Abstract
Despite the larger performance and higher throughput compared to transmission control protocol (TCP) Reno, TCP Vegas still has a few obstacles to be deployed in new networks, such as 4G LTE systems (4th Generation, Long term evolution). One of these obstacles is the Vegas congestion control that is not used in all available bandwidth capacity of the network path and which causes minimization in packet quantity transferred from source to destination. However, many researches have shown unfair treatment of TCP Vegas connections when they compete with Reno connections. So, Vegas need more developments and more modifications to be efficient over bidirectional links with unbalanced traffic, and on wireless links. TCP-Vegas is a congestion control algorithm that reduces queuing and packet loss, and thus reduces latency and increases overall throughput, by carefully matching the sending rate to the rate at which packets are successfully being drained by the network. This paper presents results from a series of simulation experiments designed to study TCP Vegas performance in LTE network model using NS-2 network simulator. The characterization and analysis of Vegas behavior performed using the main two parameters, alpha and beta, to configure the congestion window (cwnd) phases. After used multiple values, the configuration results show that TCP Vegas perform better than TCP Reno. Key words: Transmission control protocol; TCP-Vegas, cwnd, long term evolution (LTE), NS-2.
Highlights
transmission control protocol (TCP) Vegas is a modification of TCP Reno introduced by Brakmo and Peterson (1994)
Despite the larger performance and higher throughput compared to transmission control protocol (TCP) Reno, TCP Vegas still has a few obstacles to be deployed in new networks, such as 4G long term evolution (LTE) systems (4th Generation, Long term evolution)
The NS-2 codes used in our experiments use TCP Vegas to change the default and individual parameters of congestion control algorithm over LTE connections
Summary
TCP Vegas is a modification of TCP Reno introduced by Brakmo and Peterson (1994). Vegas employs three techniques to increase throughput and decreases the packet loss, which are new retransmission mechanism, a congestion avoidance mechanism and a modified slowstart mechanism. TCP-Vegas is a proactive congestion control mechanism proposed to improve TCP performance by using round trip time (RTT) as a main parameter to monitor traffic condition and avoid congestion (Hong et al, 2006). TCP-Vegas detects congestion at an incipient stage based on increasing RTT values of the packets in the connection unlike other flavors like Reno, which detect congestion only after it has happened via packet drops. The actual flow rate will be smaller than the expected flow rate, and Vegas using this difference in flow rates to estimate the congestion level in the network and updates
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