IRI - chap5

1

copy From Computer Networking by KuroseampRoss 5 DataLink Layer 5-1

Introduction toComputer Networking

Guy Leduc

Chapter 5Link Layer and LANs Computer Networking

A Top Down Approach5th editionJim Kurose Keith RossAddison-Wesley April2009


Chapter 5 The Data Link LayerOur goals understand principles behind data link layer

services error detection sharing a broadcast channel multiple access link layer addressing reliable data transfer flow control done

instantiation and implementation of various linklayer technologies

2


Link Layer

51 Introduction andservices

52 Error detection 53Multiple access

protocols 54 Link-layer

Addressing 55 Ethernet

56 Link-layer switches 57 PPP 58 Link virtualization 59 A day in the life of a

web request


Link Layer IntroductionSome terminology hosts and routers are nodes communication channels that

connect adjacent nodes alongcommunication path are links wired links wireless links LANs

layer-2 packet is a frameencapsulates datagram

data-link layer has responsibility of transferring datagram from one node to adjacent node over a link

3


Link layer context datagram transferred by

different link protocolsover different links eg Ethernet on first link

frame relay onintermediate links 80211on last link

each link protocolprovides differentservices eg may or may not

provide rdt over link

transportation analogy trip from Princeton to

Lausanne limo Princeton to JFK plane JFK to Geneva train Geneva to Lausanne

tourist = datagram transport segment =

communication link transportation mode =

link layer protocol travel agent = routing

algorithm


Link Layer Services framing link access

encapsulate datagram into frame adding header trailer channel access if shared medium ldquoMACrdquo addresses used in frame headers to identify

source destbull different from IP address

reliable delivery between adjacent nodes we learned how to do this already (chapter 3) seldom used on low bit-error link (fiber some twisted

pair) wireless links high error rates

bull Q why both link-level and end-end reliability

4


Link Layer Services (more)

flow control pacing between adjacent sending and receiving nodes

error detection errors caused by signal attenuation noise receiver detects presence of errors

bull drops framebull if recovery needed signals sender for retransmission

error correction receiver identifies and corrects bit error(s) without resorting

to retransmission half-duplex and full-duplex

with half duplex nodes at both ends of link can transmit butnot at same time


Where is the link layer implemented

in each and every host link layer implemented in

ldquoadaptorrdquo (aka networkinterface card NIC) Ethernet card PCMCI

card 80211 card implements link physical

layer attaches into hostrsquos

system buses combination of

hardware softwarefirmware

controller

physicaltransmission

cpu memory

host bus (eg PCI)

network adaptercard

host schematic

applicationtransportnetwork

link

linkphysical

5


Adaptors Communicating

sending side encapsulates datagram in

frame adds error checking bits

rdt flow control etc

receiving side looks for errors rdt flow

control etc extracts datagram passes

to upper layer at receivingside

controller controller

sending host receiving host

datagram datagram

datagram

frame


Link Layer





56 Link-layer switches 57 PPP 58 Link Virtualization 59 A day in the life of a

web request

6


Error DetectionEDC= Error Detection (and sometimes Correction) bits (redundancy)D = Data protected by error checking may include header fields

bull Error detection not 100 reliablebull protocol may miss some errors but rarelybull larger EDC field yields better detection (and correction)

otherwise


Parity CheckingSingle Bit ParityDetect single bit errors

Two Dimensional Bit ParityDetect and correct single bit errors

0 0

7


Internet checksum (review)

Sender treat segment contents as

sequence of 16-bitintegers

checksum addition (1rsquoscomplement sum) ofsegment contents

sender puts checksumvalue into UDP checksumfield

Receiver compute checksum of

received segment check if computed checksum

equals checksum field value NO - error detected YES - no error detected

But maybe errorsnonetheless

Goal detect ldquoerrorsrdquo (eg flipped bits) intransmitted packet (note used at transport layeronly)


Checksumming Cyclic Redundancy Check

view data bits D as a binary number choose r+1 bit pattern (generator) G goal choose r CRC bits R such that

ltDRgt exactly divisible by G (in base-2 arithmetic) receiver knows G divides ltDRgt by G If non-zero remainder

error detected can detect all burst errors less than or equal to r bits (see later)

widely used in practice (Ethernet 80211 WiFi PPP ATM)

8


CRC ExampleWant

D2r XOR R = nGequivalently

D2r = nG XOR Requivalently if we divide D2r by G

(in base-2 arithmetic)want remainder R

r=3

R = remainderD 2r

G

$

amp

(

Divisor

Quotient

Dividend

In base-2 arithmetic-no carries-no borrows


CRC Example the polynomial view

Transmitted frameT(x) = D(x) xr - R(x)

Is divisible byG(x)

D(x) = x5 + x3 + x2 + xr=3G(x) = x3 + 1

R(x) = remainderD(x) xr

G(x)

$

amp

(

9


Why does it work We have T(x) = D(x) xr - R(x)

Therefore the remainder of T(x) G(x) is zero This is easy to check at the receiver provided that the

sender and the receiver agree on a certain G(x) Suppose some errors occur during transmission

The received frame is T(x) + E(x) The receiver will then calculate the remainder of

(T(x) + E(x)) G(x) This remainder is equal to the remainder of E(x) G(x) If there is an error such that E(x) is not divisible by

G(x) it is detected The choice of G(x) is thus very important

From Computer Networks by Tanenbaum copy Prentice Hall


Example of CRC Generator = G(x) = x16 + x12 + x5 + 1 G(x) detects every E(x) consisting of an odd number of error bits

Because G(x) is a factor of x + 1 (in base-2 arithmetic G(1) = 0)and a polynomial E(x) with an odd number of terms is not divisible by x+1 (in base-2arithmetic E(1) = 1 for such E(x))

More generally a G(x) composed of an even number of terms detects everyerror consisting of an odd number of error bits At least as good as a parity bit Could a parity bit be seen as a trivial CRC Any G(x) to suggest

G(x) detects every 2-bit error (in any place in the frame) G(x) detects every error burst of length le 16 bits

An error burst of length n (ge 2) is 1 erroneous bit followed by n-2 bits (correct or not)followed by an erroneous bit

So an error burst of length le 16 bits is an E(x) = Ersquo(x) xk with neither Ersquo(x) nor xk beingdivisible by G(x) because Ersquo(x) is of degree le 15 while G(x) is of degree 16

More generally a G(x) of degree r detects every r-bit error bursts G(x) detects 99997 of the 17-bit error bursts (if errors are random) G(x) detects 99998 of the 18-bit error bursts (if errors are random)


10


Link Layer






web request


Multiple Access Links and ProtocolsTwo types of ldquolinksrdquo point-to-point

PPP for dial-up access point-to-point link between Ethernet switch and host

broadcast (shared wire or medium) old-fashioned Ethernet upstream HFC 80211 wireless LAN

shared wire (eg cabled Ethernet)

shared RF (eg 80211 WiFi)

shared RF(satellite)

humans at acocktail party

(shared air acoustical)

11


Multiple Access protocols single shared broadcast channel two or more simultaneous transmissions by nodes

interference collision if node receives two or more signals at the same time

multiple access protocol distributed algorithm that determines how nodes

share channel ie determine when node can transmit communication about channel sharing must use channel

itself no out-of-band channel for coordination


Ideal Multiple Access Protocol

Broadcast channel of rate R bps1 when one node wants to transmit it can send at

rate R2 when M nodes want to transmit each can send at

average rate RM (fairness)3 fully decentralized

no special node to coordinate transmissions no synchronization of clocks slots

4 simple

12


MAC Protocols a taxonomyThree broad classes Channel Partitioning

divide channel into smaller ldquopiecesrdquo (time slotsfrequency code)

allocate piece to node for exclusive use Random Access

channel not divided allow collisions ldquorecoverrdquo from collisions

ldquoTaking turnsrdquo nodes take turns but nodes with more to send can take

longer turns


Channel Partitioning MAC protocols TDMA

TDMA time division multiple access access to channel in rounds each station gets fixed length slot (length = pkt

transmission time) in each round unused slots go idle example 6-station LAN 134 have pkt slots 256

idle

1 3 4 1 3 4

6-slotframe

13


Channel Partitioning MAC protocols FDMA

FDMA frequency division multiple access channel spectrum divided into frequency bands each station assigned fixed frequency band unused transmission time in frequency bands go idle example 6-station LAN 134 have pkt frequency

bands 256 idlefr

eque

ncy

band

stime

FDM cable


Random Access Protocols

When node has packet to send transmit at full channel data rate R no a priori coordination among nodes

two or more transmitting nodes ldquocollisionrdquo random access MAC protocol specifies

how to detect collisions how to recover from collisions (eg via delayed

retransmissions) Examples of random access MAC protocols

slotted ALOHA ALOHA CSMA CSMACD CSMACA

14


Slotted ALOHA

Assumptions all frames have same

size time is divided into

equal size slots (time totransmit 1 frame)

nodes start to transmitonly at slot beginning

nodes are synchronized if 2 or more nodes

transmit in slot allnodes detect collision

Operation when node obtains fresh

frame transmits in nextslot if no collision node can

send new frame in nextslot

if collision noderetransmits frame ineach subsequent slotwith prob p untilsuccess


Slotted ALOHA

Pros single active node can

continuously transmit atfull rate of channel

highly decentralizedonly slots in nodes needto be in sync

simple

Cons collisions wasting slots idle slots nodes may be able to

detect collision in less thantime to transmit packet

clock synchronization

15


Slotted Aloha efficiency

Suppose N nodes with many frames tosend each transmits in slot withprobability p Note not exactly slotted ALOHA

prob that node 1 has success in a slot =p(1-p)N-1

prob that any node has a success =Np(1-p)N-1

For max efficiency with Nnodes find p that maximizesNp(1-p)N-1

p = 1N For many nodes take limit of

Np(1-p)N-1 = (1-1N)N-1

as N goes to infinityit gives 1e = 037

Efficiency is the long-runfraction of successful slotswhen there are many nodes eachwith many frames to send

At best channelused for useful transmissions 37of time

limN

1$G

N

amp

(

)

N

= e$G


Pure (unslotted) ALOHA unslotted Aloha simpler no synchronization when frame first arrives

transmit immediately collision probability increases

frame sent at t0 collides with other frames sent in [t0-1t0+1]

In frame time units

16


Pure Aloha efficiencyP(success by given node) = P(node transmits) P(no other node transmits in [t0-1t0] P(no other node transmits in [t0t0+1] = p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)

P (success by any node) = Np (1-p)2(N-1)

hellip choosing optimum p and then letting n go to infinity

= 1(2e) = 018

Even worse than slotted Aloha


Efficiency wrt average trafficload Let G = pN be the average aggregated traffic load

(or demand) per frame time = nr of transmission attempts per frame time N stations sending one frame with probability p in every

frame time Efficiency

Slotted ALOHA Np(1-p)N-1 = G (1-GN)N-1

ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)

Efficiency (for a given G) when N gtgt Slotted ALOHA G e-G

ALOHA G e-2G

If G ltlt 1 efficiency asymp G perfect

limN

1$G

N

amp

(

)

N

= e$G

17


Efficiency Optimum out of 100 frame times- 37 are used effectively- 26 are collisions- 37 are just empty


ALOHA versus Slotted ALOHA

frame


CSMA (Carrier Sense Multiple Access)

CSMA listen before transmitIf channel sensed idle transmit entire frame If channel sensed busy defer transmission

LBT Listen Before Talking (and deference)

human analogy donrsquot interrupt others

18


CSMA collisions

collisions can still occurpropagation delay meanstwo nodes may not heareach otherrsquos transmission

collisionentire packet transmissiontime wasted

spatial layout of nodes

noterole of distance amp propagationdelay in determining collisionprobability


persistent CSMA(if channel is busy listen until it isfreed)

non persistent CSMA(if channel is busy program anew attempt later)

p-persistent CSMAWhile true doif channel is freethen

with probability p immediate transmission or

with probability 1-p stay idle during at least propagation time (τ) else listen until the channel is freed

Trade-off between efficiency and delaybull This introduces a useless delay at low loadsbull But the efficiency of the channel is better at high loads

p-persistent CSMA

19


Efficiency

Efficiency versus load for various randomaccess protocols


frame


B = Channel Data Rate (so-called Bandwidth) (bps)F = (Maximum) Frame size (bits)L = Length of the channel (m)c = Propagation speed (ms)

τ = Propagation delay = L c (s)T = Transmission delay = F B (s)

a = τ T = BL cFLet a = 1 rarr F = 100 BL c = plusmn 5 10-7 BL (with c = plusmn 200000 kms)Let B = 10 Mbps L = 25 km rarr F = 12500 bits (= 15625 bytes)This is roughly the Ethernet frame size

Engineering a CSMA network

20


CSMACD (Collision Detection)CSMACD carrier sensing deferral as in CSMA

collisions detected within short time colliding transmissions aborted reducing channel

wastage collision detection

easy in wired LANs measure signal strengthscompare transmitted received signals

difficult in wireless LANs received signal strengthoverwhelmed by local transmission strength

human analogy the polite conversationalist


CSMACD collision detectionCSMACD CSMA

Lost time le 2 τ(worst case 2 max propagation timeswhen the 2 stations are at the 2 ends)+ detectabort time No abort so loss is T

21


To detect collision the sender must still be transmitting when the collisionpropagates back to it So the condition is

T gt 2τ which means FB gt 2 Lcwhich leads to a minimal Fmin = 2BLc = plusmn BL 10-8 bits

Let B = 10 Mbps L = 25 km rarr Fmin = plusmn 250 bits (= plusmn 32 bytes) Ethernet has chosen 64 bytes = 512 bits (extra margin due to other delays)

A B

(a)

A B

(b)

A B

(c)

A B

(d)Collision attime τ

Noise burst getsback to A at 2τ

Packet startsat time 0

Packet almostat B at τminusε

Minimal frame size with CSMACD



ldquoTaking Turnsrdquo MAC protocols

channel partitioning MAC protocols share channel efficiently and fairly at high load inefficient at low load delay in channel access

1N bandwidth allocated even if only 1 activenode

Random access MAC protocols efficient at low load single node can fully

utilize channel high load collision overhead

ldquotaking turnsrdquo protocolslook for best of both worlds

22


ldquoTaking Turnsrdquo MAC protocolsPolling master node

ldquoinvitesrdquo slave nodesto transmit in turn

typically used withldquodumbrdquo slave devices

concerns polling overhead latency single point of

failure (master)

master

slaves

poll

data

data


ldquoTaking Turnsrdquo MAC protocolsToken passing control token passed

from one node to nextsequentially

token message concerns

token overhead latency single point of failure

(token)

T

data

(nothingto send)

T

23


Summary of MAC protocols

channel partitioning by time frequency or code Time Division Frequency Division

random access (dynamic) ALOHA S-ALOHA CSMA CSMACD carrier sensing easy in some technologies (wire) hard in

others (wireless) CSMACD used in Ethernet CSMACA used in 80211

taking turns polling from central site token passing Bluetooth FDDI IBM Token Ring


Link Layer



protocols 54 Link-Layer



web request

24


MAC Addresses and ARP

32-bit IP address network-layer address used to get datagram to destination IP subnet

MAC (or LAN or physical or Ethernet)address function get frame from one interface to another

physically-connected interface (same network) 48-bit MAC address (for most LANs)

bull burned in NIC ROM also sometimes software settable


LAN Addresses and ARPEach adapter on LAN has unique LAN address

Broadcast address =FF-FF-FF-FF-FF-FF

= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN(wired orwireless)

25


LAN Address (more)

MAC address allocation administered by IEEE manufacturer buys portion of MAC address space

(to assure uniqueness) analogy (a) MAC address like Social Security Number (b) IP address like postal address MAC flat address portability

can move LAN card from one LAN to another IP hierarchical address NOT portable

address depends on IP subnet to which node is attached


ARP Address Resolution Protocol

Each IP node (hostrouter) on LAN hasARP table

ARP table IPMACaddress mappings forsome LAN nodes

lt IP address MAC address TTLgt TTL (Time To Live) time

after which addressmapping will be forgotten(typically 20 min)

Question how to determineBrsquos MAC addressknowing Brsquos IP address

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26


ARP protocol Same LAN (network)

A wants to send datagramto B and Brsquos MAC addressnot in Arsquos ARP table

A broadcasts ARP querypacket containing Bs IPaddress dest MAC address =

FF-FF-FF-FF-FF-FF all machines on LAN

receive ARP query B receives ARP packet

replies to A with its (Bs)MAC address frame sent to Arsquos MAC

address (unicast)

A caches (saves) Brsquos IP-to-MAC address pair in itsARP table until informationbecomes old (times out) soft state information

that times out (goes away)unless refreshed

All other stations had alsocached Arsquos IP-to-MAC pair

ARP is ldquoplug-and-playrdquo nodes create their ARP

tables withoutintervention from netadministrator


Addressing routing to another LAN

R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A

walkthrough send datagram from A to B via R assume A knows Brsquos IP address

two ARP tables in router R one for each IPnetwork (LAN)

27


A creates IP datagram with source A destination B In routing table at source Host find Rrsquos IP = 111111111110 A uses ARP to get Rrsquos MAC address for 111111111110 A creates link-layer frame with Rs MAC address as dest

frame contains A-to-B IP datagram Arsquos NIC sends frame Rrsquos NIC receives frame R removes IP datagram from Ethernet frame sees itrsquos

destined for B R uses ARP to get Brsquos MAC address R creates frame containing A-to-B IP datagram sends to B

R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A

This is a really importantexample ndash make sure youunderstand


Link Layer


52 Error detection

53Multiple accessprotocols

54 Link-LayerAddressing

55 Ethernet


web request

28


Ethernetldquodominantrdquo wired LAN technology cheap $20 for NIC first widely used LAN technology simpler cheaper than token LANs and ATM kept up with speed race 10 Mbps ndash 10 Gbps

Metcalfersquos Ethernetsketch


Star topology bus topology popular through mid 90s

all nodes in same collision domain (can collide with eachother)

today star topology prevails active switch in center each ldquospokerdquo runs a (separate) Ethernet protocol (nodes

do not collide with each other)

switch

bus coaxial cable star

29


Ethernet Frame StructureSending adapter encapsulates IP datagram (or other

network layer protocol packet) in Ethernet frame

Preamble 7 bytes with pattern 10101010 followed by one

byte with pattern 10101011 used to synchronize receiver sender clock rates


Ethernet Frame Structure (more) Addresses 6 bytes

if adapter receives frame with matching destinationaddress or with broadcast address (eg ARP packet) itpasses data in frame to network layer protocol

otherwise adapter discards frame Type indicates higher layer protocol (mostly IP

but others possible eg Novell IPX AppleTalk) CRC checked at receiver if error is detected

frame is dropped

30


Ethernet Unreliable connectionless

connectionless No handshaking between sending andreceiving NICs

unreliable receiving NIC doesnrsquot send acks nor nacksto sending NIC stream of datagrams passed to network layer can have gaps

(missing datagrams) gaps will be filled if app is using TCP otherwise app will see gaps

Ethernetrsquos MAC protocol unslotted CSMACD


Ethernet CSMACD algorithm1 NIC receives datagram

from network layercreates frame

2 If NIC senses channel idlestarts frame transmissionIf NIC senses channelbusy waits until channelidle then transmits

3 If NIC transmits entireframe without detectinganother transmission NICis done with frame

4 If NIC detects anothertransmission whiletransmitting (collision)aborts and sends jamsignal

5 After aborting NICenters exponentialbackoff after mthcollision NIC chooses K atrandom from012hellip2m-1 NIC waitsK512 bit times returns toStep 2

31


Ethernetrsquos CSMACD (more)Jam Signal make sure all

other transmitters areaware of collision 48bits

Bit time 01 microsec for 10Mbps Ethernetfor K=1023 wait timeis about 50 msec

Exponential Backoff Goal adapt retransmission

attempts to estimatedcurrent load heavy load random wait

will be longer first collision choose K from

01 delay is K 512 bittransmission times

after second collision chooseK from 0123hellip

after ten collisions choose Kfrom 01234hellip1023

with this backoff algorithmEthernet is sort ofp-persistent CSMA with anadaptive p

Seeinteract with Javaapplet on AWL Web sitehighly recommended


S = T (T + α times 2τ)= 1 (1 + α times 2τT)= 1 (1 + α times 2BLcF )For large N α convergestowards e (plusmn27) for ap-persistent CSMA withp = 1N (ideal case)

So for N gtgt S cannotbe better than1 (1 + e times 2τT)= 1 (1 + 54 τT)

Number of active stations = N

Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames


Channel efficiency of an adaptivep-persistent CSMA

Let α = the average number of slots (2 τ) before any successful transmission

32


8023 Ethernet Standards Link amp Physical Layers

many different Ethernet standards common MAC protocol and frame format different speeds 2 Mbps 10 Mbps 100 Mbps

1 Gbps 10 Gbps different physical layer media fiber cable


linkphysical

MAC protocoland frame format

100BASE-TX

100BASE-T4

100BASE-FX100BASE-T2

100BASE-SX 100BASE-BX

fiber physical layercopper (twistedpair) physical layer


Manchester encoding

used in 10BaseT each bit has a transition allows clocks in sending and receiving nodes to

synchronize to each other no need for a centralized global clock among nodes

Hey this is physical-layer stuff

33


Manchester encoding - Signaldistortion

Transmittedsignal

Receivedsignal

after 1200 mon RG11 coax

Manchester signal at 4Mbps


Link Layer


52 Error detection 53 Multiple access




web request

34


Hubshellip physical-layer (ldquodumbrdquo) repeaters

bits coming in one link go out all other links at samerate

all nodes connected to hub can collide with oneanother

no frame buffering no CSMACD at hub host NICs detect collisions

twisted pair

hub


Switch link-layer device smarter than hubs take

active role store forward Ethernet frames examine incoming framersquos MAC address selectively

forward frame to one-or-more outgoing links whenframe is to be forwarded on segment usesCSMACD to access segment

transparent hosts are unaware of presence of switches

plug-and-play self-learning switches do not need to be configured

35


Switch allows multiple simultaneoustransmissions

hosts have dedicateddirect connection to switch

switches buffer packets Ethernet protocol used on

each incoming link but nocollisions full duplex each link is its own collision

domain switching A-to-Arsquo and B-

to-Brsquo simultaneouslywithout collisions not possible with dumb hub

A

Arsquo

B

Brsquo

C

Crsquo

switch with six interfaces(123456)

1 2 345

6


Switch Table

Q how does switch know thatArsquo reachable via interface 4Brsquo reachable via interface 5

A each switch has a switchtable each entry (MAC address of host interface

to reach host time stamp) Is a MAC forwarding table

Looks like an IP forwarding table Q how are entries created

maintained in switch table something like a routing

protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36


Switch self-learning

switch learns which hostscan be reached throughwhich interfaces when frame received

switch ldquolearnsrdquo location ofsender incoming LANsegment

records senderlocationpair in switch table

A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo

MAC addr interface TTLSwitch table

(initially empty)A 1 60


Switch frame filteringforwardingWhen frame received

1 record link associated with sending host2 index switch table using MAC dest address3 if entry found for destination

then if dest on segment from which frame arrived

then drop the frame else forward the frame on interface indicated else flood forward on all but the interface

on which the frame arrived

37


Self-learningforwardingexample

A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo



A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo frame destination

unknown flood

Arsquo A

destination Alocation known

Arsquo 4 60

selective send


Interconnecting switches

switches can be connected together

A

B

Q sending from A to F - how does S1 know how toforward frame destined for F via S4 and S2

A self learning (works exactly the same as insingle-switch case)

S1

C D

E

FS2

S4

S3

HI

G

38


Self-learning multi-switch exampleSuppose C sends frame to I I responds to C

Q show switch tables and packet forwarding in S1S2 S3 S4

A

B

S1

C D

E

FS2

S4

S3

HI

G

12


Institutional network

to externalnetwork

router

IP subnet

mail server

web server

39


All principles seen so far are applicable to a subnet withseveral switches if there is no cycle in the topology No cycle = no redundancy in case of failure

Part of subnet can be disconnected

A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2


More than one switch in asubnet


Problem Frame F (whose destination address is unknown to bothswitches) will loop

Solution build a logical spanning tree topology over the real topology

LAN 1

LAN 2

FInitial frame

F1 F2

Frame copiedby left switch

Frame copiedby right switch


Problem with cycles

40


Build a logical tree reaching allLANs

1 Determine the root switch(smallest switch id)

Switches regularly flood controlmessages (BPDUs) on all theiroutput ports

BPDU = ltSource switch id root asassumed distance to rootgt

All switches will soon discoverthe root id

A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch


Spanning tree (1)Root switch A sends ltAA0gt on LAN1 and LAN2

B sends ltBA1gt on LAN 3


2 Build the tree By continuously receiving these

BPDUs (possibly on severalports) a switch knows itsdistance to the root and whichport leads to the root by thatshortest distance (root port r)

A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr


Spanning tree (2)Root portRoot switch

41


3 Decide if non-root ports are (data)forwarding or (data) blockingA port is forwarding (f) on a givenLAN if the BPDUs this switch sendson this LAN are smaller thanthose other switches (would) send

Smaller = shorter distance or equaldistance and smaller switch id

Exampleon LAN6 E sends ltEA2gt G would sendltGA2gt and J would send ltJA3gtSo E is elected to be the only one toforward frames on LAN6 J is too faraway from the root and G gt E

A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f

Spanning tree (3)Forwarding port

Blocking port



Some switches (eg G and J) are not part of the tree Another case could be that some ports of some switches are blocking

They could become part of the tree if another switch or port would fail(leading to no refresh of BPDUs)

So switches have to listen to BPDUs on blocking ports to detect failures

1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN

Switch thatis part of the

spanning tree

Switch that isnot part of thespanning tree

I

The resulting spanning treeRouting on a spanning treeis not optimal

Same spanning tree for allsource-destination pair

Compare to layer-3 routing


42


Switches vs Routers both store-and-forward devices

routers network layer devices (examine network layerheaders)

switches are link layer devices routers maintain IP routing and IP forwarding

tables implement routing algorithms switches maintain MAC forwarding tables

implement filtering learning and spanning treealgorithms

Switch


Summary comparison

hubs routers switches

traffic

isolation

no yes yes

plug amp play yes no yes

optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer





56 Hubs and switches 57 PPP 58 Link Virtualization 59 A day in the life of a

web request


Point to Point Data Link Control one sender one receiver one link easier than

broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line ADSL line

popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control

bull Data link used to be considered ldquohigh layerrdquo inprotocol stack

44


PPP Design Requirements [RFC 1557]

packet framing encapsulation of network-layerdatagram in data link frame carry network layer data of any network layer

protocol (not just IP) at same time ability to demultiplex upwards

bit transparency must carry any bit pattern in thedata field

error detection (no correction) connection liveness detect signal link failure to

network layer network layer address negotiation endpoint can

learnconfigure each otherrsquos network address


PPP non-requirements

no error correctionrecovery no flow control out of order delivery OK no need to support multipoint links (eg polling)

Error recovery flow control data re-ordering all relegated to higher layers

45


PPP Data Frame

Flag delimiter (framing) Address does nothing (only one option) Control does nothing in the future possible

multiple control fields Protocol upper layer protocol to which frame

delivered (eg PPP-LCP IP IPCP etc)


PPP Data Frame

info upper layer data being carried check cyclic redundancy check for error

detection

46


Byte Stuffing - Principle ldquodata transparencyrdquo requirement data field must

be allowed to include flag pattern lt01111110gt Q is received lt01111110gt data or flag

Sender adds (ldquostuffsrdquo) extra lt01111110gt byteafter each lt01111110gt data byte

Receiver two 01111110 bytes in a row discard first byte

continue data reception single 01111110 flag byte


Byte Stuffing - Variant of PPP

flag bytepatternin datato send

flag byte pattern plusstuffed escape byte intransmitted data

47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

The original data (the frame payload)

Bit stuffing the data as they appear on the line

The data as they are stored in the receiverrsquos memory after destuffing

Bit stuffing rule for that flag add a 0 after five 1s alwaysSo no flag pattern in the payload

Rule remove 0 after five 1s If six 1s in a row check if it is a flag

Bit stuffingUsed in other data link protocolsUse same flag as delimiter = 01111110



Link Layer





56 Hubs and switches 57 PPP 58 Link Virtualization a

Network as a Link Layer 59 A day in the life of a

web request

48


The Internet virtualizing networks

ATM or MPLS or Ethernet net satellite net

IP router

Internetwork layer (IP) addressing internetwork

appears as a single uniformentity despite underlying localnetwork heterogeneity

network of networks

Router ldquoembed IP packets in local

packet format or extract themrdquo route (at IP level) to next IP

router

Those networks are seen as virtual links by IP routers

Switch


IPentity

Non-IP ldquonetworkrdquo 1(encapsulating IP packets)

IPentity

IProuter

IPpackets

IPpackets

Global Internetwork (IP) Service


IP over anything (not just linksor isolated LANs)

Transportentity

Transportentity

Examples-Network 1 can be a subnet composed of one or several Ethernet switches-Network 2 can be a large ATM or MPLS backbone network

Seen as a link by IP Seen as a link by IP

49


Link Layer







web request


Synthesis a day in the life of a web request

journey down protocol stack complete application transport network link

putting-it-all-together synthesis goal identify review understand protocols (at

all layers) involved in seemingly simple scenariorequesting www page

scenario student attaches laptop to campusnetwork requestsreceives wwwgooglecom

50


A day in the life scenario

Comcast network 68800013

Googlersquos network 64233160019 64233169105

web server

DNS server

school network 68802024

browser

web page


A day in the lifehellip connecting to the Internet

connecting laptop needs toget its own IP address addrof first-hop router addr ofDNS server use DHCP

router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP

DHCP request encapsulatedin UDP encapsulated in IPencapsulated in 8021Ethernet

Ethernet frame broadcast(dest FFFFFFFFFFFF) on LANreceived at router runningDHCP server

Ethernet demuxrsquoed to IPdemuxrsquoed UDP demuxrsquoed toDHCP

51



DHCP server formulatesDHCP ACK containingclientrsquos IP address IPaddress of first-hoprouter for client name ampIP address of DNS server

router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

encapsulation at DHCPserver frame forwarded(switch learning) throughLAN demultiplexing atclient

Client now has IP address knows name amp addr of DNS server IP address of its first-hop router

DHCP client receives DHCPACK reply


A day in the lifehellip ARP (before DNS before HTTP) before sending HTTP request

need IP address of wwwgooglecomDNS

DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS query created encapsulatedin UDP encapsulated in IPencasulated in Eth In order tosend frame to router need MACaddress of router interface ARP

ARP query broadcast receivedby router which replies withARP reply giving MAC addressof router interface

client now knows MAC addressof first hop router so can nowsend frame containing DNSquery

ARP query

EthPhy

ARP

ARP

ARP reply

52


A day in the lifehellip using DNS

DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS

IP datagram containing DNSquery forwarded via LANswitch from client to 1st hoprouter

IP datagram forwarded fromcampus network into comcastnetwork routed (tables createdby RIP OSPF IS-IS andorBGP routing protocols) to DNSserver

demuxrsquoed to DNS server DNS server replies to

client with IP address ofwwwgooglecom


DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS


A day in the lifehellip TCP connection carrying HTTP

HTTPTCPIP

EthPhy

HTTP

to send HTTP requestclient first opens TCPsocket to web server

TCP SYN segment (step 1in 3-way handshake) inter-domain routed to webserver

TCP connection established64233169105web server

SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

web server responds withTCP SYNACK (step 2 in 3-way handshake)

53


A day in the lifehellip HTTP requestreply

HTTPTCPIP

EthPhy

HTTP

HTTP request sent intoTCP socket

IP datagram containingHTTP request routed towwwgooglecom

IP datagram containingHTTP reply routed back toclient

64233169105web server

HTTPTCPIP

EthPhy

web server responds withHTTP reply (containingweb page)

HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

web page finally ()displayed


Chapter 5 Summary principles behind data link layer services

error detection sharing a broadcast channel multiple access link layer addressing

instantiation and implementation of various linklayer technologies Ethernet switched LANs

bull learning building spanning tree PPP Link virtualization networks as a link layer

54


Chapter 5 letrsquos take a breath journey down protocol stack complete (except PHY) solid understanding of networking principles practice hellip could stop here hellip but lots of interesting topics

Multicasting Wireless networks Mobility Multimedia networking Secure networking Network management

2


Link Layer





56 Link-layer switches 57 PPP 58 Link virtualization 59 A day in the life of a

web request


Link Layer IntroductionSome terminology hosts and routers are nodes communication channels that

connect adjacent nodes alongcommunication path are links wired links wireless links LANs

layer-2 packet is a frameencapsulates datagram

data-link layer has responsibility of transferring datagram from one node to adjacent node over a link

3












algorithm








4

















controller


cpu memory

host bus (eg PCI)

network adaptercard

host schematic


link

linkphysical

5











datagram datagram

datagram

frame


Link Layer






web request

6




otherwise




0 0

7


















8


CRC ExampleWant




r=3

R = remainderD 2r

G

$

amp

(

Divisor

Quotient

Dividend





Is divisible byG(x)

D(x) = x5 + x3 + x2 + xr=3G(x) = x3 + 1


G(x)

$

amp

(

9


















10


Link Layer






web request










11













4 simple

12







longer turns





idle

1 3 4 1 3 4

6-slotframe

13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




3












algorithm








4

















controller


cpu memory

host bus (eg PCI)

network adaptercard

host schematic


link

linkphysical

5











datagram datagram

datagram

frame


Link Layer






web request

6




otherwise




0 0

7


















8


CRC ExampleWant




r=3

R = remainderD 2r

G

$

amp

(

Divisor

Quotient

Dividend





Is divisible byG(x)

D(x) = x5 + x3 + x2 + xr=3G(x) = x3 + 1


G(x)

$

amp

(

9


















10


Link Layer






web request










11













4 simple

12







longer turns





idle

1 3 4 1 3 4

6-slotframe

13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




4

















controller


cpu memory

host bus (eg PCI)

network adaptercard

host schematic


link

linkphysical

5











datagram datagram

datagram

frame


Link Layer






web request

6




otherwise




0 0

7


















8


CRC ExampleWant




r=3

R = remainderD 2r

G

$

amp

(

Divisor

Quotient

Dividend





Is divisible byG(x)

D(x) = x5 + x3 + x2 + xr=3G(x) = x3 + 1


G(x)

$

amp

(

9


















10


Link Layer






web request










11













4 simple

12







longer turns





idle

1 3 4 1 3 4

6-slotframe

13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




5











datagram datagram

datagram

frame


Link Layer






web request

6




otherwise




0 0

7


















8


CRC ExampleWant




r=3

R = remainderD 2r

G

$

amp

(

Divisor

Quotient

Dividend





Is divisible byG(x)

D(x) = x5 + x3 + x2 + xr=3G(x) = x3 + 1


G(x)

$

amp

(

9


















10


Link Layer






web request










11













4 simple

12







longer turns





idle

1 3 4 1 3 4

6-slotframe

13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




6




otherwise




0 0

7


















8


CRC ExampleWant




r=3

R = remainderD 2r

G

$

amp

(

Divisor

Quotient

Dividend





Is divisible byG(x)

D(x) = x5 + x3 + x2 + xr=3G(x) = x3 + 1


G(x)

$

amp

(

9


















10


Link Layer






web request










11













4 simple

12







longer turns





idle

1 3 4 1 3 4

6-slotframe

13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




7


















8


CRC ExampleWant




r=3

R = remainderD 2r

G

$

amp

(

Divisor

Quotient

Dividend





Is divisible byG(x)

D(x) = x5 + x3 + x2 + xr=3G(x) = x3 + 1


G(x)

$

amp

(

9


















10


Link Layer






web request










11













4 simple

12







longer turns





idle

1 3 4 1 3 4

6-slotframe

13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




8


CRC ExampleWant




r=3

R = remainderD 2r

G

$

amp

(

Divisor

Quotient

Dividend





Is divisible byG(x)

D(x) = x5 + x3 + x2 + xr=3G(x) = x3 + 1


G(x)

$

amp

(

9


















10


Link Layer






web request










11













4 simple

12







longer turns





idle

1 3 4 1 3 4

6-slotframe

13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




9


















10


Link Layer






web request










11













4 simple

12







longer turns





idle

1 3 4 1 3 4

6-slotframe

13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




10


Link Layer






web request










11













4 simple

12







longer turns





idle

1 3 4 1 3 4

6-slotframe

13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




11













4 simple

12







longer turns





idle

1 3 4 1 3 4

6-slotframe

13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




12







longer turns





idle

1 3 4 1 3 4

6-slotframe

13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




13




bands 256 idlefr

eque

ncy

band

stime

FDM cable








14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




14


Slotted ALOHA












Slotted ALOHA




simple




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




15








Np(1-p)N-1 = (1-1N)N-1




limN

1$G

N

amp

(

)

N

= e$G





In frame time units

16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




16



= p (1-p)2(N-1)



= 1(2e) = 018







ALOHA Np(1-p)2(N-1) = G (1-GN)2(N-1)


ALOHA G e-2G


limN

1$G

N

amp

(

)

N

= e$G

17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




17





frame






18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




18


CSMA collisions












p-persistent CSMA

19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




19


Efficiency



frame






20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




20











21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




21





A B

(a)

A B

(b)

A B

(c)

A B














22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




22






failure (master)

master

slaves

poll

data

data






(token)

T

data

(nothingto send)

T

23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




23








Link Layer






web request

24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




24










= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53


25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




25


LAN Address (more)












1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788

26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




26








address (unicast)








R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




27





R

1A-23-F9-CD-06-9B

222222222220111111111110

E6-E9-00-17-BB-4B

CC-49-DE-D0-AB-7D

111111111112

111111111111

A74-29-9C-E8-FF-55

222222222221

88-B2-2F-54-1A-0F

B222222222222

49-BD-D2-C7-56-2A



Link Layer


52 Error detection



55 Ethernet


web request

28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




28









switch


29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




29











frame is dropped

30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




30














31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




31

















Channel efficiency

S10

09

08

07

06

05

04

03

02

01

0 1 2 4 8 16 32 64 128 256

1024 byte frames

512 byte frames

256 byte frames

128 byte frames

64 byte frames




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




32






linkphysical


100BASE-TX

100BASE-T4





Manchester encoding




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




33



Transmittedsignal

Receivedsignal




Link Layer






web request

34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




34






twisted pair

hub







35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




35








A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6


Switch Table






protocol

A

Arsquo

B

Brsquo

C

Crsquo


1 2 345

6

36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




36






A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo









37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




37



A

Arsquo

B

Brsquo

C

Crsquo

1 2 345

6

A Arsquo

Source ADest Arsquo




unknown flood

Arsquo A


Arsquo 4 60

selective send




A

B



S1

C D

E

FS2

S4

S3

HI

G

38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




38




A

B

S1

C D

E

FS2

S4

S3

HI

G

12



to externalnetwork

router

IP subnet

mail server

web server

39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




39




A B

LAN 1

C D E

F G H

LAN 4

LAN 3LAN 2






LAN 1

LAN 2

FInitial frame

F1 F2




Problem with cycles

40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




40







A B2

C31

LAN

4

G

I

D E F

6 75

H J8 9

Switch







A B2

C31 4

G

I

D E F

6 75

H J8 9

r

r

r

rr

r

r

rr



41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




41





A B2

C31 4

G

I

D E F

6 75

H J8 9

rf

r

r

rr

r

r

rr

f f f

f f f

f f


Blocking port






1 2 3 4

5 6 7

8 9

A B C

D E F

H

LAN


spanning tree


I





42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




42







Switch


Summary comparison


traffic

isolation

no yes yes


optimal

routing

no yes no

cut

through

yes no yes

Some do

43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




43


Link Layer






web request






44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




44













45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




45


PPP Data Frame





PPP Data Frame


detection

46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




46











47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




47


0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0

0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0 0 1 0

Stuffed bits

0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0









Link Layer







web request

48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




48




IP router



network of networks



router


Switch


IPentity


IPentity

IProuter

IPpackets

IPpackets




Transportentity

Transportentity



49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




49


Link Layer







web request







50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




50





web server

DNS server


browser

web page




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCPDHCP




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




51




router(runs DHCP)

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCPUDP

IPEthPhy

DHCP

DHCP

DHCP

DHCP

DHCP







DNSUDP

IPEthPhy

DNS

DNS

DNS




ARP query

EthPhy

ARP

ARP

ARP reply

52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




52



DNSUDP

IPEthPhy

DNS

DNS

DNS

DNS

DNS






DNS serverDNSUDP

IPEthPhy

DNS

DNS

DNS

DNS



HTTPTCPIP

EthPhy

HTTP




SYN

SYN

SYN

SYN

TCPIP

EthPhy

SYN

SYN

SYN

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK

SYNACK


53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




53



HTTPTCPIP

EthPhy

HTTP





HTTPTCPIP

EthPhy


HTTP

HTTP

HTTPHTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP

HTTP







54




54




IRI - chap5

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