OPTIMIZATION AND PERFORMANCE ANALYSIS OF TCP OVER VARIOUS ROUTING ALGORITHMS IN UMTS WCDMA NETWORKS

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OPTIMIZATION AND PERFORMANCE ANALYSIS OF TCP OVER V ARIOUS ROUTING

ALGORITHMS IN UMTS WCDMA NETWORKS

NEETU SHARMA 1 & VIJAY SINGH RATHORE 2 1Department of Computer Engineering, Gyan Vihar University, Jaipur, Rajasthan, India

2Department of Computer Engineering, Shri Karni Group of Institutions, Jaipur Rajasthan, India

ABSTRACT

Universal Mobile Telecommunication Network (UMTS) deal with various packet losses. These packet losses

developed in network due to channel fading and shadowing. Contention in network should maintain by TCP end-to-end

semantics and dependency on intermediate nodes is minimized. Recent development of advanced 3G networks and

services makes it necessary for improving TCP’s efficiency and resource utilization. In this paper, we use TCP Tahoe

protocol to compare the Performance of two dynamic state routing protocols for 3G networks is: RIP (Routing Information

Protocol) and OSPF (Open Shortest Path First). RIP and OSPF are based on similar dynamic state routing, the differences

is only in the protocol implementation methods that can escort to significant concert differentials. These protocols are

inspected based on ‘traffic sent (packets/seconds)’, ‘traffic received (packets/seconds)’ and TCP connection

(Congestion Window)’, by using TCP Tahoe algorithm.

KEYWORDS: Universal Mobile Telecommunication System (UMTS), Transmission Control Protocol Tahoe

(TCP Tahoe), Routing Information Protocol (RIP), OSPF (Open Shortest Path First), Operational Network Evaluation Tool

(OPNET)

INTRODUCTION

Third Generation (3G) technology is revolutionizing the capabilities of mobile communications. 3G mobile

networks are expected to provide more enhanced services rather than existing cellular systems; including higher bit rates

services and greater capacity and service capability. Universal Mobile Telecommunications System (UMTS) is a

3G wireless technology offering data rates up to 2Mbps. The rapid development of wireless network technologies, such as

UMTS, WiFi and WiMAX, is making it imperative to design and optimize wireless networks to get maximum benefit with

minimal cost. Being dominant in wired networks, and due to the desire for internetworking between wired and wireless

networks, Transmission Control Protocol (TCP) has become the most commonly used transport protocol in mobile Internet

technology built on wireless cellular networks [1]. TCP is a reliable connection-oriented protocol employing a

window-based congestion control mechanism to avoid network congestion [2]. TCP uses a congestion control algorithm to

control the amount of data that the sender can inject into the network [3]. On opening a connection, the TCP sender enters

the slow start phase in which congestion window (cwnd) is increased by one maximum size segment (MSS) per

acknowledgement (ack) received[9]. Exponential growth ensues until cwnd reaches the slow-start threshold (ssthresh)

when it enters the congestion avoidance phase [6]. During congestion avoidance, cwnd is incremented by 1 MSS per RTT

and this phase continues until congestion is detected. When a TCP sender detects segment loss using the retransmission

timer, it will enter into slow start. Else fast retransmit is triggered if the sender receives a third duplicate acknowledgement

International Journal of Computer Science Engineering and Information Technology Research (IJCSEITR) ISSN(P): 2249-6831; ISSN(E): 2249-7943 Vol. 4, Issue 5, Oct 2014, 73-82 © TJPRC Pvt. Ltd.

74 Neetu Sharma, Vijay Singh Rathore

Impact Factor (JCC): 6.8785 Index Copernicus Value (ICV): 3.0

(dupack) before timeout occurs. It then retransmits the lost segment, saves ssthresh as half of the current cwnd and

increments cwnd by 1 MSS for each additional dupack. When the next ack arrives it acknowledge it as new data, cwnd is

set to the ssthresh and the TCP fast recovery phase ends [8]. Sender reduces its cwnd, or enters into slow start, even if the

segment loss isdue to a temporary wireless effect rather than congestion. To improve TCP performance over wireless

networks fall into three broad categories: link layer solutions, split connection schemes and extensions to TCP itself [4].

The rest of the paper is organized as follows. Section2 gives an overview of UMTS architecture and routing protocols.

Section 3. Shows the OPNET simulation environment of UMTS. TCP performance simulation and results with various

routing algorithm and its OPNET model are given in Sections 4. The conclusions drawnand ideas for future work are

presented in Section 5.

UMTS PROTOCOL OVERVIEW

Universal Mobile Telecommunications System (UMTS) is a third Generation (3G) wireless network. UMTS is

likely to deliver low-cost, high-capacity mobile communications, offering data rates up to 2Mbps. 3G UMTS network

consists of three interacting domains: Core Network (CN), UMTS Terrestrial Radio Access Network (UTRAN) and User

Equipment (UE). The UE is the user equipments and the UTRAN consists with base stations (Node Bs) and radio network

controller (RNC) [5]. RNC connected with node b via Iub interface. UMTS Terrestrial Radio Access Network (UTRAN)

[5] and User Equipment (UE) are composed of various layers. The four lowest layers are: physical layer (PHY), the

Medium Access Layer (MAC), Radio Link Layer (RLC) [5] and Radio Resource Layer (RRC) in UMTS network.

Figure 1: UMTS Architecture

Figure 1 shows the UTRAN architecture. The CN includes the serving GPRS support node (SGSN) and the

gateway GPRS support node (GGSN). The various routing protocols that used in UMTS are:

A. RIP

RIP protocol is based on distance-vector protocol. To compute shortest paths RIP uses the distributed

Bellman–Ford algorithm. Each router uses RIP to exchange routing information with its neighboring routers. Each route

has a metric or cost associated with it, which is the hop count to the destination. The maximum hop count is limited to 15,

and a hop count of 16 is used to represent infinity. RIP provide a limit on the number of hops allowed in a path from the

source to destination to prevent routing loops. Routing Information Protocol has three versions: RIPv1, RIPv2, and RIPng.

1. RIP Version 1

RIP[11] uses classful routing. Subnet information not carried by periodic routing updates, perform in network.

So it does not support variable length subnet masks (VLSM). RIP does not support the VLSM so it is impossible to have

Optimization and Performance Analysis of TCP Over Various Routing Algorithms in UMTS WCDMA Networks 75


dissimilar sized subnets inside of the same network class. RIP does not provide support for router authentication, making

RIP exposed to various attacks.

2. RIP Version 2

Various deficiencies are in original RIP [11] specification. Due to deficiencies RIP version 2 and last standardized

in 1998. RIP2 recover the deficiencies in original RIP and support Classless Inter-Domain Routing (CIDR) by including

the ability to carry subnet information. The hop count limit of 15 remained to maintained backward compatibility. RIPv2

do not send routing table to host that not participate in routing. It multicast the routing table only to neighboring routers at

the particular addresses that participates in routing as opposite to RIPv1 which uses broadcast.

3. RIPng

Specifications of RIPng [11] are designed work as an IGP (Interior Gateway Protocol) in moderate. It is not

anticipated for use in more complex environments. RIPng is a distance vector protocol. RIP uses the hop count as a routing

metric. RIPng protocol computes the routes by exchanging the route information with other through an IPv6-based

network. Each network Contain Metric and IPv6 destination address prefix, prefix length associated with IPV6 Destination

address. RIPng is implemented on each router and each router contain routing table. Routing table contain one entry for

every destination node that is reachable throughout the system. RIP time to converge and scalability are not good and a hop

limit reduces the size of the network so RIP is not preferably used for routing. However, it is easy to configure on network,

because RIP does not necessitate any parameters on a router disparate other protocols.

(B) OSPF

Open Shortest Path First (OSPF) is a link-state routing protocol. In OSPF [11], each router sends link-state

advertisements (LSAs) to all other routers in its domain. Link state database (LSDB) is prepared on each router that

maintained the received link-state information. which is essentially a representation of the entire network topology. Upon

receiving link-state information, each router uses Dijkstra’s shortest path first (SPF) algorithm to independently calculate

the shortest paths to all destinations. The transmission of LSAs is done via a modified flooding algorithm, which

propagates them quickly to all routers but prunes duplicate updates. As a result, OSPF is quick to detect changes in

topology such as link failures and converges very quickly to relatively loop-free routes as compared to RIP. OSPF

associates and externally specified cost metric with each link. The cost may represent link bandwidth or any other desired

parameter such as distance, delay, reliability, and so on. When there are multiple paths of equal cost to a destination, OSPF

includes all these paths in its routing table and in the IP Forwarding Table. This allows IP to do load balancing across

equal-cost paths to a given destination.

OPNET SCENARIO

The As shown in Figure 2 UMTS simulation model consist of five user equipment (UE), one node B

(base station) access point, RNC[4], SGSN[4], GGSN[4] and a switch is used for authentication which is between ftp

server and GGSN (here we can use more than one server for different multimedia data) and an FTP server which provide

its application to mobile node. This represents the OPNET model of UMTS network. RIP & OSPF is chooses as the

Protocol to measure the performance of the network. TCP Tahoe is chosen to measure the congestion window on various

nodes of the network. The simulation model used the OPNET built-in application distribution models [12]. The built-in



OPNET application profiles were used to closely simulate traffic generated by a wireless data user. The application profiles

used was the FTP profiles. This profile was combined and parameterized in order to define the UMTS client application

profile. Packet Discarder utility is used to drop the packets at various time intervals to closely calculate the performance of

RIP and OSPF routing algorithm over TCP Tahoe.

Figure 2: Snapshot of Simulation Scenario of UMTS

The simulation is performed using OPNET 14.5 Modeler and results are obtained for UMTS network under

Routing Information Protocol (RIP) and Open Shortest Path First (OSPF). Simulation time is 600 seconds and simulation

is performed in logical network that provides soft limits to the parameters. For evaluation of performance under protocols

RIP and OSPF parameters to be considered and their values for these parameters are:

Table 1: Simulation Parameter

Simulation Parameters Value Simulation Time 600 Sec Number of Nodes 05 Environment Size Logical Environment Traffic Type Constant Bit Rate Seed 128 Value per Statistics 100 Update Interval 500000

Simulation Based on Kernel type Preferences

Number of runs One for each scenario

SIMULATION RESULTS AND DISCUSSIONS

This simulation result is analyzed from the scenario 1 for 05 users for TCP Tahoe performance for RIP routing

protocol in Figure 3 and scenario 2 for 05 users also for TCP Tahoe for OSPF routing protocol in. Here we analyze the

performance of routing algorithm by implement the TCP Tahoe. For transmission of packets initially a request is sent from

Node B to SGSN through RNC, after receiving acknowledgment of request from SGSN, connection is established between

sender and receiver.



(a) Scnerio1 Observations

Scnerio1 depict the configuration of UMTS network which uses the RIP routing protocol for sending and

receiving the packets over the network. TCP Tahoe performance is analyzed over RIP protocol by congestion window, sent

segment sequence number and traffic send and receives through RIP protocol.

Figure 3: Snapshot for TCP Tahoe for RIP Routing Protocol

Scnerio2 Observations

Scenario 2 depict the configuration of UMTS network which uses the OSPF routing protocol for sending and

receiving the packets over the network. TCP Tahoe performance is analyzed over OSPF protocol by congestion window,

sent segment sequence number and traffic sent by OSPF routing protocol.

Figure 4: TCP Tahoe Performance for OSPF Routing Protocol

SIMULATION RESULTS

Global Statics

Both scenarios show different results for various statistics. First we collect the global statistics for OSPF & RIP

protocols. Figure 5 graph shows the traffic send and received for both OSPF & RIP routing protocols. The graph depicts

that OSPF send more FTP data rather than RIP on TCP Tahoe connection.



Figure 5: Traffic Sent & Received OSPF and RIP

Figure 6 graph sows the Network Convergence Activity for OSPF & RIP. This graph shows that RIP shows less

convergence activity rather than OSPF.

Figure 6: Network Convergence Activity for OSPF & RIP

Node Statistics

The number of statistics is collected on various nodes in the UMTs network. Node statistics is collected for TCP

Tahoe connection for both RIP & OSPF routing algorithm. Figure 7 graph shows the TCP congestion window on FTP

server for both OSPF & RIP algorithm.

Figure 7: TCP Tahoe Congestion Window Size at FTP Server for OSPF and RIP



Figure 8: TCP Connection Delay

Figure 9: TCP Tahoe Congestion Window for RIP & OSPF at UE_1

Figure 10: TCP Tahoe Connection Delay at UE_2 for OSPF & RIP

From the TCP performance summary on RIP & OSPF routing protocols, shown in graphs, it is also observed that

our performance evaluation for TCP Tahoe shows that size of the congestion window for OSPF is greater than RIP.

It shows that as higher the congestion window size it increases the number of packets send and minimize the congestion on

network. If size of the congestion window reduces means less number of packets is being transferred. Results show on FTP

server and also on UEs and it significantly shows the TCP Tahoe performance on OSPF is better than RIP with high packet

error rates.



CONCLUSIONS

We have proposed and implemented a TCP Tahoe protocol for two different routing algorithms i.e. RIP & OSPF.

Various statistics is collected for both routing algorithm for a secure TCP Tahoe connection. The results show the

congestion window for both routing algorithm using secure TCP Tahoe connection. Congestion window is decreases when

the congestion level increase and increases the congestion window when the congestion level goes down in network. Delay

is also calculated for both scenarios. We model UMTS network and run the simulation to validate the model by comparing

its performance with that of the standard TCP Tahoe connection on different routing algorithm over UMTS model. The

simulation results showed that the congestion is significantly reduces in TCP Tahoe OSPF model as the congestion

window of OSPF is greater than then in RIP. OSPF performs better under TCP Tahoe rather than RIP. In future work we

implement this model for other QOS classes. This model is only send and receives the FTP traffic. So it only implement for

background classes. Further we enhance the number of nodes of users and check its performance according to increase the

size of network. Furthermore this model can be extended to support the handover and mobility management with high level

of Quality of Service.

ACKNOWLEDGEMENTS

Authors are greatful to Gyan Vihar University Jaipur for providing support to carried out this research work.

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OPTIMIZATION AND PERFORMANCE ANALYSIS OF TCP OVER VARIOUS ROUTING ALGORITHMS IN UMTS WCDMA NETWORKS

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