Analysis of TCP-Reno and TCP-Vegas over AOMDV Routing Protocol for Mobile Ad Hoc Networks

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In TCP-Reno, when the packet loss occurs, a TCP receiver sends a duplicate ACK immediately while a TCP sender utilizes a fast retransmit mechanism, where the arrival of 3 duplicate ACKs indicates that a packet has been lost and recovers the missing packet without waiting for a retransmission timer to expire. A fast recovery algorithm, in turn, governs the transmission of new data packets until a non-duplicate ACK arrives.

TCP-Vegas introduces a proactive congestion avoidance technique which does not violate the congestion avoidance paradigm of TCP. It is able to utilize extra bandwidth without the network congestion and oscillation in window size, whereas TCP Reno always updates its window size to guarantee full bandwidth utilization, which leads to packet losses constantly.

In order to test performance in a large-scale network, node speed and the offered traffic load are varied in 100 nodes random topologies, and packet loss rate, throughput, NRL and average delay are measured as performance metrics. TCP-Reno performs better than TCP-Vegas in the analysis of packet loss rate, throughput and NRL, except average delay. Even though TCP-Vegas controls network congestion with a delay estimate scheme, it is difficult to obtain a precise estimate in mobile environment, where packet losses are likely to be due to node movement and wireless channel errors. TCP Vegas suffers worse than TCP-Reno whereas its estimation scheme helps to reduce average delay. Even though TCP Reno’s packet losses detection mechanism gets worse average delay, it offers significant performance improvement in all background changes.

On the other hand, AOMDV’s core mechanism that salvages packet losses by maintaining the next hop information in the routing tables is mutually advantageous over itself and transport protocols when node mobility and traffic loads increases. All in all, TCP-Reno is the best protocol to apply in MANET with AOMDV routing protocol if compared with TCP-Vegas.

Source:
Mazliza Othman and May Zin Oo, “Analysis of TCP-Reno and TCP-Vegas over AOMDV Routing Protocol for Mobile Ad Hoc Networks“, Proc. of the 12th International Conference on Advanced Communication Technology (ICACT 2010), pp. 1104-1108, 7 – 8 February, 2010, Phoenix Park, Korea (ISBN:978-89-5519-145-5)