International Journal of Computer Applications (0975 – 8887) Volume 108 – No 20, December 2014 24 Proportional Study of TCP Variants over Heterogeneous Wireless Networks Abdul Razaque Computer Science Department University of Bridgeport CT-06604, USA Khaled Elleithy Computer Science Department University of Bridgeport CT-06604, USA ABSTRACT Transmission control protocol (TCP) was initially designed for static networks to provide the consistent data delivery. The enhancement of TCP performance was also achieved with different types of networks with the introduction of new TCP deviations. However, there are still many factors that affect the performance of TCP. Mobility is one of the primary performance-affecting drivers in heterogeneous network. The research of state in this paper is to determine the best TCP variant from the mobility point of view. We simulate some TCP variants such as TCP-Tahoe, TCP-Reno, TCP-New Reno, TCP- Vegas, TCP-SACK and TCP-Westwood from the mobility point of view. The scenarios presented in this paper are supported by on- demand link weight (ODLW) routing protocol that helps find the efficient route with Quality of Service (QoS) provisioning. The scenarios are designed for the walking persons to vehicles, and particularly suited for rocky and deserted areas. To demonstrate the strength of these TCP variants, the scenarios are simulated and evaluated the QoS parameters such as round trip time (RTT) fairness, end-to-end delay, and the number of broken links. Finally, based on the outcomes, we identify the best TCP variant that could be used for several applications in the future over heterogeneous wireless networks. General Terms Wireless communication networks, experiments and simulation. Keywords TCP variants, heterogeneous network, RTT, throughput, broken links, end-to-end delay 1. INTRODUCTION The fact is that the TCP was originally designed for the wired network, and even its good performance is in the wired network[1].The researchers have put their efforts for improving the performance of TCP in wireless networks, and all this work confirmed that TCP in its present structure is not appropriate for MANET[2]. TCP has high overhead due to packet loss that may cause the buffer congestion because the MANET’s losses is due to an error or the frequently of the mobility [3]. So, the TCP cannot be efficient in current form[4]. Furthermore, the main reason of the weak performance of the standard TCP in the wireless network is the inability of discovering the lost packets[5]. So, we can realize that both characteristics have the same reason of packet loss, which is the based on the network congestion[6]. However, some new protocols have been introduced and implemented to avoid packet loss due to congestion. We evaluate some of the existing TCP variants, and then demonstrate how they in a heterogeneous network particularly MANET. The MANET network is a particular network due to the ability of its nodes to communicate with each other via intermediate nodes. So, it can be set up in any remote areas without infrastructure-based support. The nodes, which are the part of MANET require the data and information from the database. However, the database is available in a wired network. Therefore, MANET can be integrated with wired network to obtain the required data and information [7]. Some applications run over the database, which are supported by TCP variants. This paper aims to exhibit the weaknesses and strengths of TCP variants in the heterogeneous network especially MANET. Simulation is conducted using NS2. TCP variants use different congestion control mechanisms, which include congestion window, recovery mechanism, retry limit, maximum packet size and backup mechanism[8]. To determine the performance for each TCP variants, as new architecture and approaches are required to find out complete behavior of the variants. This motivation results to introduce such network to analyze the effectiveness for each TCP Variants. The random waypoint mobility model is also used for controlling the moments of nodes. In order to analyze the impact of mobility in the heterogeneous network, it is essential that underlying mobility model should attain the realistic scenario or at least significant features. To this conclusion, we deem that this paper makes the reasonable contribution. The scope of this paper is to analyze some existing TCP variants over heterogeneous network. The focus of study is particularly around the performance metrics such as throughput, RTT fairness, end-to-end delay, and broken links in presence of the mobility. The remaining paper is organized as follows. In Section 2, we present related work. In Section 3, we present heterogeneous network design. In Section 4, we explain handover process. In Section 5, we present simulation setup and analysis of the result. In Section 6, we present the discussion of the results and finally section 7 concludes the work and future directions. 2. RELATED WORK In this section, we present the salient features of existing TCP variants. The performance of TCP Reno, New Reno, SACK and Tahoe was evaluated in [9]with respect to goodput under three routing protocols over static multi-hop network. The authors demonstrated that Reno had edge over other TCP variants. However, the scenario was not fully explained. Our work is entirely different from their work because we use