A Proposed Technique for Solving

the Triangle Routing Problem in Mobile IP

Eng. Sherif Kamel Hussein Ph.D. Student

A. Prof. Imane Aly Saroit Ismail Information Technology Department

Faculty of Computers and Information

Cairo University

Prof. S. H. Ahmed Vice Dean

Faculty of Computers and Information

Cairo University Abstract:

Mobile IP has seen slow deployment for two major reasons; the need for enhancing

edge routers with Home Agent/Foreign Agent functionality and the fact that triangle routing

in such systems is not efficient. Triangle Routing is defined as the route that must be taken

through the Home Agent for any traffic sent by the Correspondent Node to the Mobile Node.

This route is triangle in nature and longer than the normal path between the Corresponded

Node and the Mobile Node. Many protocols and research efforts have been developed to

solve this problem.

This paper proposes a technique called Internet Service Provider Mobile IP Border

Gateway (ISP MBG) for solving the Triangle Routing Problem in conventional Mobile IP

protocol using the Internet Service Providers separated by a Mobile IP Border Gateways

(MBGs). This proposed technique has been implemented and tested on the Microsoft.net

platform. Simulation results prove that the new framework has solved the Triangle Routing

Problem in Mobile IP by providing a shorter route with a minimum transmission time for all

the datagrams transferred between the Correspondent Nodes and the Mobile Nodes.

Keywords: Mobile IP, Triangle Routing Problem, Route Optimization, Internet Service

Provider, Point of Presence, Mobile IP Border Gateway, PoPs Virtual Network.

Abbreviations:Correspondent Node (CN), Care-of-Address (CoA), Foreign Agent (FA),

Home address (Ha), Home Agent (HA), Internet Service Provider (ISP), Mobile Node (MN),

Point-of-Presence (PoP), Mobile IP Border Gateway (MBG), PoPs Virtual Network (PVN).

حل مشكمة المسار المثمثي في بروتوكول اإلنترنت المتحركأسموب مقترح ل

داء محاددي آوذلاك لباببين ميماين ا:ولال ايحتيارى تلاي تحادي رئايلقد أبدى بروتوكول اإلنترنت المتحرك انتشاررًا ب تييااا لتواياااد مشاااكم المبااارر لياااذأل ا:ن مااا ن متكااار داء الغيااار ربااالعاللميل ا:ينبااالان الاااارنلال اآالمباااررات عاللميااال ا:ب

المباارر الااذي تتبلاا البيرناارت التاال ترباال ماان اللقاادع المرباام تلااي اللقاادع عمااي أناا المباارر المامااال ويمكاان تلرياا المامااال ومماار ااو ياادير برلااذكر أن ناارك مييااودًا ممحو ااًر ااد بااذل لحاال المتحركاا وذلااك ماان ماارل الماارور عباار اللمياال ا:برباال

مال ل بروتوكول اإلنترنتمشكم المبرر الماو ااو ماار لحاال مشااكم المباارر المامااال اال بروتوكااول اإلنترناات المتحاارك التقمياادي أباامو اال ااذا البحاا يااتم ا تاارا و

عماي اباتمدام اللدياد مان مازودي ويلتماد ا:بامو المقتار مزودي مدمرت اإلنترنت ذات بوابارت الحادود ببروتوكول يبميا ااذا MBGsتاال تل اال عاان بلسااير بربااتمدام بواباارت الحاادود لبروتوكااول اإلنترناات المتحاارك عمدماا شاابكرت اإلنترناات وال

ا:بامو المقتار المحركارع أن نتارئ و اد أابتات ميكروباو ت نتعن ريق اباتمدام اللمل المقتر و د تم امتبرر ومحركرعدي وذلاك عان رياق تتبارا مبارر أ ار ما تقميال بحل مشكم المبرر المامال ل بروتوكول اإلنترنت المتحرك التقميا د رم

زمن اإلربرل ليمي البيرنرت المربم من اللقدع المربم تلل اللقدع المتحرك

- - 2

1. Introduction

The two most powerful technology trends nowadays (The Internet and Mobile

Communication) are redefining the idea of how and when people access information. Now,

new devices like cellular phones and laptops and business practices are pushing the need for

"always on IP connectivity", or in other words the desire to have continuous network

connectivity to the internet regardless of the physical location of the node. The internet

protocol (IP) requires that hosts on any network have stationary IP addresses, by which the

host is uniquely identified. However, problems rise when a host starts to move away from its

Home Network since it has to change its IP address. Since the IP protocol requires that each

host has a fixed IP address in order to be reached, the moving host will no longer be

reachable [1].

Mobile IP is an open standard, defined by the Internet Engineering Task Force (IETF)

RFC 2002, that allows users keep the same IP address, stay, connected, and maintain ongoing

applications while roaming between networks, given that any media that can support IP can

support Mobile IP. Efforts were made to enhance the standard protocol and to be able to

achieve data transmission within the wireless infrastructure. However, in trying to achieve

this goal many problems have emerged and still proposals to solve them are evolving [2].

The key feature of Mobile IP design is that all required functionalities for processing

and managing mobility information are embedded in well-defined entities, the Home Agent

(HA), Foreign Agent (FA), and Mobile Nodes (MN). The Mobile Node is a host or router that

can change its location from one link to another without changing its IP address or

interrupting existing services. The Home Agent is a router with an interface on a Mobile

Node's home link that intercepts packets destined for the home address. It tunnels packets to

the mobi1e nodes most recently reported Care-of-Address. The Foreign Agent is a router on a

Mobile Node's visited network that provides routing services to the Mobile Node while it is

registered [3, 4].

Suppose that a Mobile Node moves from its Home Network to a Foreign Network, the

correct delivery of packets to its current point of attachment depends on the Mobile Node's IP

address, which changes at every new point of attachment. Therefore, to ensure packet delivery

to the Mobile Node, Mobile IP allows the Mobile Node to use two IP addresses: The Home

address and Care-of-Address (CoA) which is static and is used for instance, to identify TCP

connections. CoA changes at each new point of attachment and can be thought of as the

Mobile Node's topologically significant address. Whenever the Mobile Node is not attached

to its Home Network, the Home Agent gets all the packets destined for the Mobile Node and

arranges to deliver them to the Mobile Node's current point of attachment [2].

Triangle Routing Problem is considered as one of the main problems facing the

implementation of Mobile IP such as, when a Communicating Node (CN) sends traffic to the

Mobile Node, packets first get to the Home Agent, which encapsulates these packets and

tunnels them to the Foreign Agent. The Foreign Agent de-tunnels the packets and delivers

them to the Mobile Node. The route taken by these packets is triangular in nature, and the

most extreme case of routing can be observed when the Communicating Node and the Mobile

Node are in the same subnet [5, 6]. In recent literature, many protocols have been invented to

solve the Triangle Routing problem such as; Forward Tunneling and binding cache, Dynamic

Address Allocation, Bidirectional Route Optimization, and Internet Service Provider Points of

Presence (ISPPoPs) [7, 8, 9, 10].

This paper proposes a technique for solving Triangle Routing Problem in Mobile IP

based on using a number of Internet Service Providers (ISPs) separated by a multiple Mobile

IP Border Gateways (MBGs). The Internet Service Provider is allocated to provide services

for a definite number of geographical areas, each area is composed of a fixed number of zones

served by a fixed number of Points of Presence (PoPs), each PoP serving a number of nodes

- - 3

depends on their locations. Virtual networks between PoPs are established to facilitate the

accessing of the nodes' information without any redundancy. Having Mobile IP Border

Gateways (MBG) between different Internet Service Providers will maintain the data for all

the nodes, leaving their local Internet Service Provider and transferred to another Internet

Service Provider. Hence the level of security will be increased between them. A simulation

was built to evaluate this protocol; the performance of this technique was evaluated and

compared with the Conventional Mobile IP technique.

The paper is divided into seven sections. Section 2 presents some basic concepts about

Mobile IP while Section 3 introduces the concept of the Triangle Routing Problem in Mobile

IP. A fast survey of some recent protocols proposed for optimizing the Triangle Routing

Problem is also presented. Section 4 presents the proposed ISP MBG technique used to

optimize the Triangle Routing Problem in the Conventional Mobile IP technique. Section 5

introduces the analysis and evaluation of the proposed ISP MBG technique compared with the

conventional Mobile IP technique. Section 6 presents the concluding remarks. Finally,

Section 7 presents the future work.

2. Mobile IP

Mobile IP is a modification to IP that allows nodes to continue to receive datagrams no

matter where they happen to be attached to the Internet. It involves some additional control

messages that allow the IP nodes involved to manage their IP routing tables reliably.

Scalability has been a dominant design factor during the development of Mobile IP, because

in the future a high percentage of the nodes attached to the Internet will be capable of

mobility [5, 11, 12].

2. 1 Mobile IP Terminologies

Concerning the Mobile IP a set of terminologies are considered and defined as follows:

Mobile Node (MN) a host or router that changes its point of attachment from one

network or subnetwork to another

Home address (Ha) an IP address that is assigned for an extended period of time to a

Mobile Node in the Home Network.

Home Agent (HA) a router on a Mobile Node’s Home Network which tunnels

datagrams for delivery to the Mobile Node when it is away from

home, and maintains current location information for the Mobile

Node.

Home Network (HN) a network, possibly virtual, having a network prefix matching that

of a Mobile Node’s Home Address.

Foreign Agent (FA) a router on a Mobile Node’s Visited Network which provides

routing services to the Mobile Node while registered. The Foreign

Agent de-tunnels and delivers datagrams to the Mobile Node.

Foreign Network

(FN)

any network other than the Mobile Node’s Home Network.

Care-of-Address

(CoA)

the termination point of a tunnel toward a Mobile Node, for

datagrams forwarded to the Mobile Node while it is away from

home.

Correspondent Node

(CN)

a peer with which a Mobile Node is communicating, it may be

either mobile or stationary.

Link a facility or medium over which nodes can communicate at the link

layer. A link underlies the network layer.

Node a host or a router

- - 4

Tunnel the path followed by a datagram while it is encapsulated

Virtual Network a network with no physical instantiation beyond its router (with a

physical network interface on another network).

Visited Network a network other than a Mobile Node’s Home Network to which the

Mobile Node is currently connected.

Visitor List the list of Mobile Nodes visiting a Foreign Agent.

Mobile Binding the association of Home Network with a Care-of-Address, along

with the remaining lifetime of that association

2. 2 Operation of Mobile IP

Mobile IP is doing the following three relatively separate functions: Agent Discovery,

Registration and Tunneling [11, 12].

2. 2. 1 Agent discovery

The discovery process in Mobile IP is very similar to the router advertisement process defined

in Internet Control Message Protocol (ICMP). For the purpose of discovery, a router or

another network node that can act as an agent periodically issues a router advertisement ICMP

message with an advertisement extension [11, 12].

2. 2. 2 Registration

Once a Mobile Node has recognized that it has transferred on a Foreign Network and

has acquired a Care-of-Address, it needs to alert a Home Agent on its Home Network and

requests that the Home Agent forwards its IP traffics. The registration process involves four

steps: Registration Request to Foreign Agent, Foreign Agent Relays the Request to Home

Agent, Registration Reply from the Home Agent to the Foreign Agent and finally the Foreign

Agent Relays the Reply to the Mobile Node [11, 12].

2. 2. 3 Tunneling

Once a Mobile Node is registered with a Home Agent, the Home Agent must be able, to

intercept IP datagrams sent to the Mobile Node’s Home Network so that these datagrams can

be forwarded via tunneling.

In the most general tunneling case as shown in Figure 1; the source, the encapsulator,

the decapsulator and the destination are separate nodes. The encapsulator node is considered

the entry point of the tunnel, while the decapsulator node is considered the exit point of

tunnel. Multiple source-destination pairs can use the same tunnel between the encapsulator

and decapsulator [11, 12].

Figure 1. General Tunneling

Three options for encapsulation (tunneling) are available for use by the Home Agent on

behalf of the Mobile Node mainly: IP-ln-IP Encapsulation, Minimal Encapsulation, and

General Routing Encapsulation (GRE).

Encapsulation

Source

Decapsulation

Destination

Tunneling

- - 5

2. 3 Mobile IP Operation Sequence

With the three relatively separated functions; Agent Discovery, Registration and

Tunneling; a rough outlines of the operation of Mobile IP Protocol is described as shown in

Figure 2 [5].

Figure 2. Mobile IP Operation Sequence

Mobile agents (Foreign Agents and Home Agents) advertise their presence via agent-

advertisement messages. A Mobile Node receives an agent advertisement and determines

whether it is on its Home Network or a Foreign Network. When the Mobile Node detects that

it is located on its Home Network, it operates without mobility services. When a Mobile Node

detects that it has moved to a Foreign Network, it obtains a CoA on the Foreign Network. The

CoA can be either a Foreign Agent CoA or a Co-located CoA, then the Mobile Node registers

its new CoA with its Home Agent through the exchange of a registration request and

registration reply message, possibly by way of a Foreign Agent. Datagrams sent to the Mobile

Node’s Home Network are intercepted by its Home Agent, tunneled by the Home Agent to

the Mobile Node’s CoA, received at the tunnel endpoint (either at a Foreign Agent or at the

Mobile Node itself), and finally delivered to the Mobile Node. In the reverse direction,

datagrams sent by the Mobile Node may be delivered to their destination using standard IP

routing mechanisms, without necessarily passing through the Home Agent.

3. Triangle Routing Problem

One of the basic problems facing the implementation of Mobile IP is the Triangle

Routing Problem, since all the traffics between CN and MN should have to pass through a

longer path than the normal one. This section introduces the definition and the drawbacks of

the Triangle Routing Problem as shown in the following supsections.

3. 1 Triangle Routing Definition

Triangle Routing Problem is considered as one of the problems facing the

implementation of Mobile IP. When a CN sends traffics to a MN, the following sequence

must be done:

1. Packets first get the HA.

2. Home Agent encapsulates these packets and tunnels them to the FA.

3. The Foreign Agent de-tunnels the packets and delivers them to the Mobile Node.

Foreign Network

5.a. Reg.

Request

5.d. Reg.

Reply

HOME AGENT

3. Mobility

Binding

MOBILE

NODE

FOREIGN

AGENT

4.Visit list

5.b. Reg.

Request

5.c. Reg.

Reply

Correspondent

Node 7. Datagrams sent from MN to CN

Dat

a to

Mobil

e N

ode

Inte

rcep

ted b

y H

A

6.

2. Received Agent

Advertisement

1. Send Agent

Advertisement

1. Send Agent Advertisement

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As shown in Figure 3, the route taken by these packets is triangle in nature, and the most

extreme case of routing can be observed when the Correspondent Node and Mobile Node are

in the same subnet [7, 16].

Figure 3. Illustration of the Triangle Routing Problem in Mobile IPv4

3. 2 Triangle Routing Drawbacks

Conventional Mobile IP technique allows transparent interoperation between Mobile

Nodes and their Correspondent Nodes, but forces all datagrams for a Mobile Node to be

routed through its Home Agent. Thus, datagrams to the Mobile Node are often routed along

paths that are significantly longer than optimal. This indirect routing can significantly delay

the delivery of the datagrams to Mobile Nodes, and it places an unnecessary burden on the

networks and routers along its path through the internet. The Triangle Routing drawbacks can

be mentioned as follows:

1. Increases the delays per packet in datagrams transferred to the Mobile Node.

2. Wastes the network resources.

3. Home Agent bottle neck.

4. Delimits the scalability of Mobile IP protocol.

3. 3 Triangle Problem's Previous Solutions

Several research efforts were done to eliminate or address the Triangle Routing Problem

in Mobile IP [7, 8, 9, 10, 11, 12, 13, 14]. Some of such efforts are briefly mentioned as

follows:

[17, 18] presented a route optimization protocol which was developed to solve the

Triangular Routing Problem, by allowing each host to maintain a binding cache for a mobile

host wherever it is [7]. This Route Optimization technique provides a smooth handoff when

the Mobile Node moves and registers with a new Foreign Agent.

[8] presented a technique with an extension to the Mobile IP architecture. In this

technique, one Mobile Station (MS) is to handle two IP addresses between internet and intra-

domain, one is called a Current Address (CA) and another one is called a Register Address

(RA). Location Agent (LA) is a router responsible for translating both addresses between

internet and intra-domain. Register Address is used for packets routing in internet; Current

Address is used for packets in intra-domain. Mobile Agent (MA) is router on a Mobile

Station's current network which delivers packets to Mobile Station, it has a functionality

similar to FA and HA. Hard handoff technique is proposed to be used with this technique.

Also, a “packet retransmission” technique is used to avoid packet loss while hard handoff.

[9] presented a technique to support symmetric bidirectional route optimization in

Mobile IP considering ingress-filtering routers [19]. Subnet-based direct tunneling techniques

CN MN

FA

HA

Datagram MN-CN

Datagram CN- MN

Detunneld

Tunneled datagram

1

2

3

- - 7

are proposed to improve the routing efficiency for Mobile IP and a binding optimization

technique to reduce the handoff latency for Mobile Nodes. An enhanced correspondent agent

was introduced to collaborate with the Home Agent and the Foreign Agent to support these

techniques. Correspondent Agent will maintain the binding cache and intercepts all packets

sent to and from the Correspondent Nodes. Symmetrically, a Foreign Agent, at the other end

of the optimized route or tunnel, maintains a tunneling cache for bidirectional route

optimization.

[10] mentioned that, the basic idea in optimizing Triangle Routing is to get the HA as

close as possible to the MN, when the MN no longer in its Home Network. This is achieved

by shifting the Home Agent into the ISP's Domain. The ISP's network makes the Mobile IP

"aware" by enhancing ISP Points of presence (PoPs) and by creating a virtual network

composed of PoPs to distribute the state information about the MN at the original HA to all

PoPs. This ensures that no matter where the MN is, the HA is just a PoP away.

[11] presented a modified encapsulation technique is modified to give a better delay

performance for Mobile IP. Instead of encapsulation at the home agent, the encapsulation is

done at one level up in a hierarchical network. This reduces the delay of traveling the same

link twice. The processing delay is also reduced, as the processing is not centralized at the

home agent.

[12] has proposed certain extensions to Mobile IP to support route optimization. A

drawback of the proposed route optimization extensions to Mobile IP is the requirement for

the CN to be mobility aware. In this paper, the authors propose a port address translation

based route optimization technique. The proposed route optimization technique attempts to

reduce the overhead and delay involved with traditional mobile communication by means of

using port address translation (PAT) and routing the packet using an optimal path.

[13] presented a route optimization agent based, which moves the tasks of maintaining

and updating binding caches and encapsulating messages away from individual correspondent

nodes to the correspondent agents. A simulation environment has been setup to evaluate the

proposed methodology. Simulation results show that the proposed protocol outperforms the

existing protocols in terms of system message complexity, protocol simplicity, and scalability.

[14] mentioned that a permanent home address is not really necessary for many Internet

applications on a mobile host. Also, a mobile host's mobility is highly localized during a

certain period of time. By having a foreign network within a mobile host's localized footprint

to be it's virtual home network, it can greatly alleviate the triangle routing problem because of

the mobility locality nature, and, at the same time, enable the mobile host to communicate

with any conventional Internet hosts that are not mobility aware.

3. 4 Previous Route Optimization Techniques Drawbacks in Mobile IP

The great effect of using the Route Optimization techniques is to minimize the

transmission time (delay) between Correspondent Node (CN) and Mobile Node (MN) because

of the shortest path to reach Mobile Node and also to reduce the traffic and control signals

over the network. The drawbacks of the most Route Optimization techniques are classified as

follows:

1. Rigid requirements for an authentication of the clamed Care-of-Address especially when

both of Mobile Node and Correspondent Node are in different IP networks.

2. Increase the cost of hardware devices needed for the Route Optimization functions.

- - 8

3. Increase the amount of traffics over the network.

4. Increase the rate of buffering and storage buffers.

5. Increase the rate of blocking especially when the number of connections to Mobile Nodes

is increased which results in increasing in the transmission time between Correspondent

Node (CN) and Mobile Node (MN).

4. A Proposed Technique for Solving the Triangle Routing Problem

Before discussing the proposed technique it is important to mention the types of

communications in Mobile Networks. In this issue, communication types involve the

following [20]:

1. Communication between Mobile Node (MN) and Correspondent Node (CN) within the

same Network; in this case the Home Agent receives a packet destined to the Mobile

Node from a Correspondent Node and both of MN and CN are in the same network as

shown in Figure 4.

Figure 4. Connection between Two Mobile Terminals in the Same Network

2. Communication between Mobile Node (MN) and Corresponded Node (CN) in two

different Networks; when both of the Mobile Node and Correspondent Node are located

in different networks as shown in Figure 5. It is supposed for the binding information to

be transferred between the two networks and that will lead to a security related problem.

To solve this problem, Mobile IP Border Gateways (MBGs); which are devices within

the mobile networks; will maintain the binding information that must be added to the

Correspondent Node without adding functions to terminals in the external

networks [20, 21, 22].

Figure 5. Connection between Mobile Terminal and

Correspondent Node in two Different IP Networks

Other IP network

Mobile IP

network

Mobile

Terminal

FA FA

HA Gateway

Correspondent Node

HA: Home Agent

FA: Foreign Agent

Mobile IP

Core network

HA

FA FA

Mobile

Terminal

Mobile

Terminal

HA : Home Agent

FA: Foreign Agent

- - 9

4.1 Objectives of the Proposed Technique

The main objective of the proposed technique is to solve the Triangle Routing Problem

in the Conventional Mobile IP technique. The proposed technique aims are:

1. minimizing the average message delay.

2. maximizing the network throughput (minimize the network blocking rate).

3. using the network resources efficiently and eliminating the Home Agent (HA) processing

bottleneck due to the fact that all communication from Correspondent Node (CN) to

Mobile Node (MN) are necessarily routed through the Home Agent (HA).

4. increasing the level of security between different networks by using the Mobile IP Border

Gateway (MBG). This is important for maintaining the information that being used by the

Correspondent Node (CN) such as incoming packets from the external network are

tunneled or routed and delivered directly to the Mobile Node (MN) instead of routing

through the Home Agent (HA).

4. 1. 1 Architectural design of the proposed technique

Figure 6 presents the overall design of the proposed ISP MBG technique for the Route

Optimization Problem.

Figure 6. Global Views for the Proposed ISP MBG Technique

with an Example of PVN

The design introduces the following:

1. Having a number of N Internet Service Providers ISP1, ISP2,…….., ISPN each covers a

definite and different geographical place. They are separated by an L Mobile IP Border

Gateways (MBGs) [20]. MBGs will maintain either the binding (Home address, Care-of-

Address) or only the home information (Home address) for all the transferred nodes

(Mobile Nodes) from one Internet Service Provider to another. That depends on whether

we are using tunneling or routing technique to forward the traffics generated in one

Internet Service Provider and destined to Mobile Node located in another Internet Service

Agent 1

MBGL

ISP2 ISPN

MBG1

ISP1 ISPN-1

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

Zone 1 Zone 2 Zone M

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

Agent 2

Agent S-1

Agent S

Area 1

Area 2

Area S-1

Area S

PVN1

- - 10

Provider. Also, using multiple MBGs will distribute uniformly the processing load among

them.

2. Each Internet Service Provider is divided into a number of approximately S equal areas.

Each area is served by an Agent that is considered as Home Agent for the nodes within

that area and as Foreign Agent for all the nodes transferred from the other areas.

3. Each area is divided into multiple equal M zones where each zone is served by a fixed K

equal number of Points-of-Presence (PoPs).

Figure 7 shows an example of the areas and PoPs classifications of each area for an Internet

Service Provider.

Figure 7. PoPs Classifications for ISP

4. For each Internet Service Provider assuming that we have K PoPs virtual networks

(PVNs) that can be placed in a fashion that is similar to (Ping-Pong) overlay network

creation. This virtual network handles state information about all Mobile Nodes and

Correspondent Nodes. For example, when a Mobile Node registers with one Points-of-

Presence (PoPs), in one of the defined zones, the registration information will be available

to all other zones through the PVN connecting that PoP with the other equivalent PoPs in

the other zones. Figure 8 shows an example of PoPs Virtual Networks (PVNs) for ISP.

PVNi

i1..k

PoPi(Area1,Zone1), PoPi (Area1,Zone2),…, PoPi (Area1, ZoneM),

PoPi (Area2,Zone1), PoPi (Area2,Zone2), …., PoPi (Area2,ZoneM),…..,

PoPi (Areas ,Zone1), PoPi (AreaS,Zone2)……. PoPi (AreaS,ZoneM).

Figure 8. PVNs for ISP

5. Each PoP serving a definite X number of nodes with a range W of addresses. The nodes

that are within the same agent serving the PoP are called Local Nodes and those are in

different agents, and transferred to the agent serving that PoP; are called External Nodes.

The range of W addresses for each PoP is divided as follows:

1. A addresses for local nodes that are in service (Home address)

2. B addresses for local nodes that are in waiting (Home address)

3. C addresses for external nodes that are in service (Care-of- Address)

4. D addresses for external nodes that are in waiting (Care-of-Address)

ISP

Area 1

(Agent 1)

Area 2

(Agent 2)

Area S-1

(Agent S-1)

Area S

(Agent S)

Zone 1

Zone 2

Zone M-1

Zone M

PoP 1

PoP 2

PoP K-1

PoP K

- - 11

4. 1. 2 Sequences of the propose technique

When a node is generated, it will be supported by the PoP serving its position, all of the

home information concerning that node will be saved at that PoP. When a Mobile Node (MN)

moves to another area or agent, the new agent will provide the node with the Care-of-Address.

The home information for the node in the new position could be accessed through the PoP

Virtual Networks (PVNs) that connects the node's home PoP to its new position serving the

PoP. Figure 9 shows the operation sequence of the proposed technique.

The operation sequence for the proposed algorithm depends on whether both of the

Correspondent Node and the Mobile Node are located in the same Internet Service Provider

or both belong to different Internet Service Providers. So, when Correspondent Node needs to

establish connection with the Mobile Node we have the following cases:

1. Both CN and MN belong to the same Internet Service Provider.

a. CN connects to its home PoP (Pk-1)asking about the information for the Mobile Node.

b. The correspondent PoP searches its neighboring PoPs (P1, P2,….Pk-2, Pk) in the same

Zone, one of them is guaranteed to be connected to the virtual network of the Mobile

Node.

c. The PoP which is connected to the Mobile Node's Virtual Network (i.e. P1) connects

directly to the Mobile Node and the connection is established.

2. Both CN and MN belong to different Service Providers

a. The Mobile IP Boarder Gateway will keep the home information (Home address) for all

the Mobile Nodes that are transferred form one ISP to another.

b. The Correspondent Node connects to its home PoP (Pk-1) asking about the information

for the Mobile Node.

c. The Correspondent PoP will ask its neighboring PoPs (P1, P2,….Pk-2, Pk) about the

Mobile Node's home information. One of the PoPs (P1) is guaranteed to be connected

to the virtual network of Mobile Node.

d. The PoP which is connected to the MN's Virtual Network (i.e. P1) connects to MBG

which has the original home information for the destined MN. MBG connects to the

nearest PoP in the destination ISP which is connected to the new virtual network of

Mobile Node

e. The connection is established between Correspondent Node and Mobile Node.

ISP1 ISP2

Figure 9. Operation Sequence for the Proposed Technique

Agent 1

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

PoP1 PoP2

PoPK-1 PoPK

Agent 2

Area 1

Area 2

MBG

Home information for

the transferred MN

(Agent, Area, Zone,

PoP)

MN1 MN2

CN

PVN

1.c 2.e

2.d 2.a

1.a

2.b

1.b 2.c

- - 12

5. Evaluation of the Proposed Technique

Simulation modeling is based on system programming such as data structures,

flowcharts, programming languages and other tools that can be used to build up and

characterizing system performance. For simplicity, it is preferable to depend on the

simulation model.

5. 1 System Parameters

The key point for establishing any system is to define its main parameters. This section

introduces the simulation parameters, data structure and connection parameters for the

designated system respectively in the following three subsections:

5. 1. 1 Simulation parameters

A network with two Internet Service Providers is considered, each with two similar

areas. Each area is divided into two equal zones, where each zone is served by four PoPs.

Each PoP actually is serving 20 nodes with 30 addresses. The addresses are classified as 20

addresses for the nodes in service and 10 addresses for the nodes in waiting. The addresses for

the nodes in service are classified as 15 addresses for the local generating nodes and 5

addresses for the externally generating nodes. By the same way for the addresses concerning

the nodes in waiting. They are classified as 5 addresses for the local generating nodes and 5

addresses for the externally generating nodes. The addresses for the nodes are considered as

integer numbers given to each node consecutively and depend on the location of the node,

area, zone, PoP, and ISP it belongs to. Figure 10 shows an example of the nodes and address

classification for PoPi of the address classification for both PoP1 and PoP2 of area1, zone1 and

ISP1.

The total number of Zones all over the architecture design is 8 zones, each zone with 4

PoPs. The total number of PoPs is 32 PoPs and can be calculated by the following equation:

PN = PK x NZ where; PN is the total number of PoPs

PK is the number of PoPs within the Zone

NZ is the total number of Zones

Because of the total number of PoPs all over the architectural design is 32 PoPs and

each PoP is serving 20 nodes, the simulation is done for a total number of nodes equals to 640

nodes.

NT = PN x NC where; NT is the total number of generating nodes

NC is the number of generating nodes in each connection.

Figure 10. Nodes and Address Classifications for PoPi

PoP i

N1 N15 N16 N20 N21

N25

N26

N30

1-------15

Locally in

services

16-----20

Locally in

waiting

21-----25

Externally in

services

21-----25

Externally in

waiting

- - 13

5. 1. 2 Data structures

The main data structures implemented in the simulation are: nodes, PoPs, ISPs, Areas,

Agents, and Mobile IP Border Gateway (MBG). The class definitions and the structure

definitions for all the data structures are implemented using C Sharp on the Microsoft.net

platform.

5. 1. 3 Connection parameters

For the wireless communication design and implementation of the proposed technique,

the connection parameters for the implemented algorithm are the key point for running the

program. The connection parameters can be classified as follows:

1. The distance in kilometers equivalent to the distance of 1 pixel.

2. Link speed for PoP connection

3. Link speed for Agents connection

4. PoP nodes count to serve.

5. PoP nodes count to wait

6. Agent nodes count to serve

7. Agent nodes count to wait

5. 2 System Construction

Figure 11 shows the design architecture of the proposed ISP MBG technique. Each PoP

can be identified using the following three parameters respectively; ISP number, Agent

number and Zone number:

Pi = PoPj,k,l i = j,k,l where; Pi: the ith

PoP

j : Internet Service Provider number

k : Agent number

l : Zone number

Also, we have two similar PoPs Virtual Networks (PVNs) for the two Internet Service

Providers. Each is classified as follows: the first one connects all PoPs1, the second one

connects all PoPs2, the third one connects all PoPs3 and finally the fourth one connects all

PoPs4.

ISP 1 ISP2 Figure 11. Design Architecture

Zone 1 Agent 1 Zone

2

Zone 3 Agent 2 Zone 4

Zone 1 Agent 3 Zone 2

Zone 3 Agent 4 Zone

4

P1 P2

P3 P4

P1 P2

P3 P4

P1 P2

P3 P4

P1 P2

P3 P4

P1 P2

P3 P4

P1 P2

P3 P4

P1 P2

P3 P4

P1 P2

P3 P4

MBG

(1) (2)

(3) (4)

- - 14

1

1

.....

),(

zi

mm

m

PPD

1

1

.....

),(

Zm

mm

imL

PPD

5. 3 Performance Parameters

To evaluate the performance of the proposed ISP MBG technique, the following five

measuring criteria are measured: Link Distance, Transmission Time, Blocking, Buffering and

Security.

5. 3. 1 Link distance

The link distance is calculated in kilometers equivalent to the pixels distance between

the two connecting nodes through the PoP links or the Agent links (1 pixel = 0.2km). The link

distance can be calculated and formulated using the following equation:

Dt (Pi, Pz) =

Where; P: Transmission point (PoP or MBG)

D: Euclidian distance

Dt: Total link distance between two transmission points

5. 3. 2 Transmission time

Measuring the transmission time depends on the location of both Mobile Node (MN)

and Correspondent Node (CN) and whether both are located in the same area, same Internet

Service Provider or either in different areas or different Internet Service Providers. The

transmission time is calculated and formulated using the following general form of equation:

T (Pi, Pz) =

Where; P: Transmission point (PoP or MBG)

T (Pi, Pz):Total transmission time between two transmission points Pi and Pz

L: Link speed

D: Euclidian distance

5. 3. 3 Blocking

Blocking is an important parameter to measure the overall performance of the network

and its throughput. The blocking is measured as the number of blocked connections. Each

connection has a pair of connecting nodes, (i.e. N connections = 2N Nodes).

5. 3. 4 Buffering

Buffering is considered as one of the network resources that must be optimally used. In

the conventional Mobile IP technique, we have storage buffers for the agents whether they are

Home Agents or Foreign Agents. In the proposed ISP MBG technique, each PoP has its own

storage buffers which hold a limited number of nodes. The nodes are classified as nodes in

service and nodes in waiting, with a range of addresses for the nodes that are either locally

generated within the Agent (Home addresses) or imported from the other Agents. Using Point

of Presence Virtual Network (PVN) will provide an efficient tool for accessing the Node's

information between PoPs.[The measuring evaluation of this parameter is out of our scope].

5. 3. 5 Security

- - 15

It is one of the rigid requirements for the performance evaluation between the

conventional Mobile IP technique and the proposed one. It is measured as how much the

technique itself provides a self-securing technique to protect the data transferred among the

nodes located in different networks.[The evaluation of this parameter is out of our scope]

5. 4 Simulation Results

The purpose of the simulation is to evaluate the performance of the proposed technique

using Internet service Providers' PoPs and MBG compared with the conventional Mobile IP

technique. The running for the implemented algorithm is done and calculated based on

generating randomly a total number of nodes N= 640 nodes in 32 steps, each step includes 20

more nodes (i.e 10 connections). In each step, the whole algorithm is executed, and the

connection is also randomly done between each pair of nodes. To obtain real results, the

algorithm is executed many times and the comparison is done based on the average values of

the results.

5. 4. 1 Simulation results for link distance

Figures 12.a and 12.b show the total link distance and the average link distance per

connection for both the proposed ISP MBG and the conventional Mobile IP technique

respectively. It is clear that the proposed ISP MBG technique outperforms the conventional

Mobile IP technique. The route taken by the conventional Mobile IP technique has to pass

through the Home Agent which tunnels the data to the Foreign Agent. The route in the

proposed ISP MBG technique is taken through the home PoP of CN and the PoP virtual

network of MN which leads directly to the MN in case of one ISP. In case of using two

Internet service Providers the route has to pass through MBG to the MN's PoP virtual network

in the second ISP which leads directly to the MN.

At the point where no blocking appears (refer to section 5.3.3 where the number of

connections 28) the total link distance is increasing and the average link distance per

connections is almost constant, as all the entering connections will be served. At the point

where the blocking appears (refer to section 5.3.3 where the number of connections ≥ 28), the

total link distance and the average link distance will be slightly increased. As the rate of

blocking increases the total link distance is also increasing. For the case where the system is

saturated and due to the random generation of nodes and their connections are added to the

simulation, the distribution of nodes becomes more fair and the blocking is slightly decreased

which causes the average link distance to be consequently decreased.

(a) Comparison between total Link Distances

0

200

400

600

800

1000

1200

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

#of Connections (unit 10)

Dis

tanc

(km

)

ISP MBG Conventional Mobile IP

- - 16

(b) Comparison between Average Link Distances

Figure 12. Link Distance Comparison

5. 4. 2 Simulation results for transmission time

Figure 13.a and 13.b show the total transmission time and the average transmission time

(in seconds) per connection against the number of connections for both the conventional

Mobile IP technique and the ISP MBG technique respectively. The figures show a great

reduction in the transmission time using the proposed ISP MBG technique, compared with the

conventional one. That result is expected because of using PoPs and PVNs: the home

information for any node will be available anywhere among the networks and not only

restricted on the Home Agents that could be far away from the connecting nodes.

At the point where no blocking appears (refer to section 5.3.3 where the number of

connections 28) the total transmission time is increasing and the average transmission time

per connections is almost constant, as all the entering connections will be served. At the point

where the blocking appears (refer to section 5.3.3 where number of connections ≥ 28) the total

transmission time and the average transmission time are slightly increased. As the rate of

blocking increases the total transmission time is also increasing. For the case where the

system is saturated and due to the random generations of nodes and their connections are

added to the simulation, the distribution of nodes becomes more fair and the blocking is

slightly decreased which causes the average transmission time to be consequently decreased.

(a) Total Transmission Time for the Conventional and Proposed Techniques

0

50000

100000

150000

200000

250000

300000

350000

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

#of Connections ( Unit 10)

To

tal

Dis

tnac

e (k

m)

ISP MBG Conventional Mobile IP

0

1000

2000

3000

4000

5000

6000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

#of Connections ( Unit 10)

To

tal

Tra

nsm

issio

n T

ime (

sec)

ISP MBG Conventional Mobile IP

- - 17

(b) Average Transmission Time for the Conventional and Proposed Techniques

Figure 13. Transmission Time Comparison

5. 4. 3 Simulation results for blocking

Figure 14 details the average number of blocking in both the conventional Mobile IP

technique and the proposed one. Each blocked connection is considered as single pair of

connecting nodes. The figure shows that as long as the number of connections 28 (i.e.

number of nodes 560, "560= number of connections {28} x number of generating nodes in

each connection {20}") the blocking rate is almost zero in both the conventional mobile IP

technique and the proposed ISP MBG technique.

If the number of connection is increased (number of connections ≥ 28) meaning that the

number of nodes is also increased (number of nodes ≥ 560) the blocking rate will be increased

for both the conventional Mobile IP technique and the proposed one. The number of blocked

connections using the newly proposed ISP MBG technique is less than that the conventional

Mobile IP technique. In the conventional Mobile IP technique, the HA is overwhelmed with

an excessive amount of nodes' control messages compared with the proposed technique in

which the control messages are divided among the PoPs. Each PoP covers a number of nodes

and the virtual network between PoPs helps in getting the information easily.

Figure 14 Blocking Comparison

0

2

4

6

8

10

12

14

16

18

20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

#of Connections (unit 10)

Tra

nsm

issio

n T

ime (

sec)

ISP MBG Conventional Mobile IP

0

2

4

6

8

10

12

14

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

#of Connections

Blo

cked

Con

nect

ions

ISP MBG Conventional Mobile IP

- - 18

As the number of blocked connections decreased that leads to increase the number of paired

successful connections which means the throughput will be increased.

5. 4. 4 Buffering

Concerning Buffering; it has been found that the proposed ISP MBG technique provides

better buffering than that the Conventional Mobile IP technique. This is due to the fact that

using PVN with the proposed technique facilitates the process of handling and accessing

information for the nodes in correspondences between PoPs without any redundancy.

Comparatively, the conventional technique requires more buffers due to the redundancy of

having a multiple copies of nodes' home information at each PoP of the Internet service

Provider. This leads to less use of buffering storages than that of the conventional technique

which needs storage buffer for each node to hold all of its information at each PoP. Also, as a

cost wise, it has been found that the cost for the Agent's buffers is higher than that of the

PoP's buffers

5. 4. 5 Security

The Security design has a great concern in Mobile IP. The proposed ISP MBG

technique is considered as the self securing system. Using Mobile IP Border Gateway (MBG)

will keep the information (Home address or binding information) for all Mobile Nodes

crossing their network to another network. So, any CN in one network does not need to

maintain any private external information concerning the new IP network were the MNs visit

and all of the MN's information could be accessed directly so the Mobile Border Gateway.

Comparatively, the conventional Mobile IP technique needs rigid requirements for the

authentication to prevent the malicious users from interrupting the connection between MN

and CN that maintains the binding information (Ha, CoA).

6. Concluding Remarks

In this paper, a proposed technique called Internet Service Provider Mobile IP Border

Gateway (ISP MBG), has been introduced to solve the Triangle Routing Problem in

conventional Mobile IP Protocol. The design of this technique is based on using a number of

Internet Service Providers (ISPs) separated by a Multiple Mobile IP Border Gateways

(MBGs) which are used to keep the binding information or the home information for the

transferred Mobile Nodes between ISPs. Each ISP is composed of an approximately a number

of an equal areas, each is served by an Agent and is composed of a multiple equal zones.

Each zone is served by a definite number of Points of presences (PoPs). Each PoP is serving

a number of nodes with a range of addresses. Virtual Networks are used to connect the PoPs

in such a way the redundancy in keeping the nodes information will be minimized or almost

cancelled. The main function of the proposed technique is to get the shortest routing path for

the packets transferred between the Correspondent Nodes and Mobile Nodes based on the

PoPs information, PVN and the MBG.

The simulated network design of our case study is based on using two Internet Service

Providers separated by one mobile IP border gateway. Each ISP is divided into two equal

areas. Each area is divided into two equal zones and each zone is served by four points of

presence (PoPs). Each PoP is serving 20 nodes with a range of 30 addresses. The simulation

results for the Link Distance, Transmission Time, Blocking, Buffering and Security show that

the proposed (ISP MBG) technique outperforms the conventional Mobile IP technique by

minimizing the Link Distance, Transmission Time, Blocking, Buffering. Also, it gives a

higher level of security than that used with conventional Mobile IP technique.

- - 19

Table 1 summarizes the performance comparison between the conventional Mobile IP

technique and ISP MBG technique.

Table 1. Comparative Parameters for the Conventional and Proposed Techniques

Technique

Parameters

ISP MBG

Technique

Conventional Mobile IP

Technique

Link Distance Short link distance Long link distance

Transmission Time Low transmission time High transmission time

Blocking low rate of blocking High rate of blocking

Buffering - Less buffering storages

- Low cost

- More buffering storages

- High cost

Security High level of security Low level of security

The ISP MBG technique is considered to be the best suited technique for the ISPs with

larger topographical reach, because of the drastic performance improvement obtained in this

case.

This work can be considered applicable for the following: better performance related to

the criteria of measuring parameters ,no addition of external hardware devices are required,

more reliablility and flexibility of the simulation model,and scalability for using more PoPs

and nodes .

The implemented algorithm could be extendable to any number of ISPs, Areas, Zones,

PoPs, Nodes, but the evaluation will be related to the configuration of the system that is used

in building up the simulator and how much the behavior of the system is adapted to the

measuring parameters.

7. Future Work

This work can be extended to include investigation of using multiple ISPs and multiple

MBGs. In that case MBG is not only restricted to hold the home information for the nodes

crossing their local ISP or to guide in establishing the route to the MN located in an external

ISP, but rather the investigated subjects in that area are continuing enhance the functionalities

of MBG to do more advanced tasks.Such tasks include, tunneling, conditional Processes for

the route optimization, and others .Moreover, using multiple MBGs will distribute the

processing load among the MBGs.

References

1. C. Smith and D. Collins, “3G Wireless Networks”, “McGraw-Hill, United States, 2002.

2. A. Jamalipour, “The Wireless Mobile Internet”, John Wiley & Sons Ltd., England, 2003.

- - 20

3. Philip J. and Nesser II, “Survey of IPV4 Addresses in Currently Deployed IETF

standards”, Internet-drafts, draft-ietf-ngtrans-ipv4 survey-01.text, Work on Progress,

August 2001.

4. S.Choi, R.Mukhtar, J.Choi, and M.Zukerman, “Efficient Marcro Mobility Management

for GPRS IP Networks”, Optical Internet Research Center (OIRC), Korea, May 2002.

5. W.Stallings, “Wireless Communications and Networks”, Prentice Hall, New Jersey,

United States, 2002.

6. T. Janevski, “Traffic Analysis and Design of Wirless IP Netowrks”, Artech House Inc.,

Boston, London, 2003.

7. C. Perkins, “IP Mobility Support for IPV4”, RFC 3344, Work on Progress, August 2002.

8. W.Wu, W.Chen, F.Young and H.Liao, “Dynamic Address Allocation in Mobile IP”,

Department of Electrical Engineerng ,Feng Chia University ,November,11999.

9. C.Wu, A.Cheng, S.Lee, J.Ho and D.Lee, “Bi-directional Route Optimization in Mobile IP

Over Wireless LAN”, Institute of Information Science, Academia Sinica, Taiper, Taiwan,

Vol. 2,PP.1168-1172,2002.

10. “An Efficient, Global Mobile IPV4 Routing Frame Work using Internet Service provider,

Point of Presence ISP PoP”, http:\\networks.ecse.rpi.edu/papers/mip.pdf.

11. C.Kumar, N.Tyagi , Tripathi R., "Performance of Mobile IP with new Route Optimization

Technique", IEEE International Conference, Institute of Engineering and Rural Technol,

Allahadad, India, PP. 522-526, January 23-25, 2005.

12. D.Badami, N.Thanthry, T.Best, R.Bhagavathula and R.Pendse., "Port Address Translation

based Route Optimization For Mobile IP", Vehicular Technology Conference, IEEE 60th

,

Department of Electrical and Computer Engineering, Wichita State University, KS, USA,

Vol. 5, PP. 3110-3114, September 26-29, 2004.

13. R.Vadali, L.Jianhui, W.Yiqiong and C.Guohong , "Agent based Route Optimization For

Mobile IP", Vehicular Technology Conference, IEEE VTS 54th

,Department of Computer

Science and Engineering, Pennsylvania State University, University Park, PA ,USA ,Vol.

4, PP. 2731-2735, October 7-11, 2001.

14. G.Qiang and A.Acampora , "A Virtual Home Agent based Route Optimization for Mobile

IP", Wireless Communication and Networking Conference, IEEE,Center for Wireless

Communications ,California University ,San Diego, La Jolla, Ca, USA, Vol. 2, PP. 592-

596, September 23-28, 2000.

15. C. Perkins “Mobile IP”, IEEE, 50th Anniversary Communicative Issue, PP. 66-82. May

2002.[Originally Published in IEEE Communication Magazine,Vol 35 ,Number 5 ,PP. 84-

98, May 1997].

16.C. Perkins, “Mobile IP: Design Principles and Practices”, Addison-Wesley, United States,

1998.

17. B.Ayani, “Smooth Handoff in Mobile IP”, Master Thesis presented to University of

California in Berkeley, May 2005.

18. T.Hille, J.Kempt, P.Mccann, A.Singh, H.Soliman, and S.thalanany, “Low Latency

Handoffs in Mobile IPV4”, Internet-drafts, ietf-mobileip-low laterncy-handoffs-v4-05. txt,

Work on Progress, December 2003.

19. G.Montenegro, “Reverse Tunneleng for Mobile IP", RFC 3024, Work on Progress,

January 2001.

20.Y.Takagi ,T.Ihara and H.Obnishi,"Mobile IP Route Optimization Method for Next

Generation Mobile Networks", Electonics-and-Communications in Japan,Part

1,Vol.86,No.2 ,PP.31-41, February 2003.

21.M.Caesar and J.Rexford , ,"BGP Routing Policies in ISP Networks " IEEE Network,

University of California and Princeton University ,PP.5-11,November/December 2005.

- - 21

22.T.Ihara, H.Ohnishi and Y.Takagi , "Mobile IP Route Optimization Method for a Carrier-

scale IP Netowrk",The Proceedings of 6th

IEEE International Conference on Engineering

of Complex Computer Systems, ICECCS 2000, , PP. 120-121, September 11-14, 2000.