TCP-ArtaVegas: Improving the Fairness of TCP-Vegas Nima Afraz
Morteza Analoui
Faculty of Computer and IT Engineering Qazvin Branch, Islamic Azad University Qazvin, Iran
[email protected]
School of Computer Engineering Iran University of Science and Technology Tehran, Iran
[email protected]
Abstract— Despite the fact that delay based congestion control algorithms like TCP-Vegas can achieve a higher performance compared to loss based algorithms, some issues including fairness have been identified with the algorithm. These issues are preventing delay based congestion control algorithms to be widely implemented on the internet. This paper will tackle the fairness problem of TCP-Vegas with the modification of its congestion avoidance mechanism. The strength of our Modified version of TCP-Vegas, named TCP-ArtaVegas, is that the modification needs to be implemented only in the end hosts. Simulation results shows that TCP-ArtaVegas significantly improved the fairness of bandwidth allocation in heterogeneous network topologies. (Abstract) Keywords—congestion control; TCP-Vegas; transport protocol; (key words)
mechanism will not add any new parameters and only needs slight changes at the end hosts. The rest of this paper is organized as follows. A brief review of the TCP-Vegas original congestion avoidance schema is given in the next section. Fairness problem of TCPVegas is thoroughly described in section III. Section IV introduces our solution. In section V the simulation results will be reported and in section VI we will conclude our findings. II. TCP-VEGAS TCP-Vegas was developed at the University of Arizona by Lawrence Brakmo and Larry L. Peterson [2, 3]. The core idea of TCP-Vegas was using packet delay as congestion indicator instead of packet loss which have been used for congestion sign in loss-based congestion control algorithms. TCP-Vegas adjusts its congestion window by following algorithm:
I. INTRODUCTION With the Continuous growth of internet users and the number of internet based devices, it becomes more important to consider a way to provide the required bandwidth available for them. Considering the cost of implementing new network infrastructures, it will be more economic if we try to utilize the available network infrastructure and related standards or protocols. Internet traffic has attracted considerable attention to itself and Transmission control protocol (TCP) especially its congestion control mechanism which is responsible for managing network traffic. The traditional congestion control algorithms like TCP Reno [1] and other variants of loss-based congestion control algorithms are based on considering packet loss as the sign of network congestion. On the other hand delay-based congestion control algorithms like TCP-Vegas [2] are using a proactive way to detect the congestion on the network by using the amount of abrupt increment in round trip time between sender and receiver as a congestion indicator. Studies have shown that TCP-Vegas outperforms TCP Reno in utilization, throughput and packet loss [3], [4], [5]. However, there are still some issues with TCP-Vegas discussed in [6]. One of these issues is the unfairness of bandwidth allocation while TCP-Vegas connections are competing TCP Reno connections. This paper proposes a new algorithm that made some modifications to the congestion avoidance mechanism of TCP-Vegas in order to address its fairness issue. This modification on the TCP-Vegas congestion avoidance
CWND =
CWND+ 1
if
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