Simulation-based Analysis of TCP Behavior over Hybrid Wireless & Wired Networks

This paper describes an ns-based simulation analysis of TCP Tahoe, Reno, NewReno and SACK congestion control over hybrid wireless and wired networks. We compare the throughput performance between the four TCP versions. Since RTT variation statistics are used by some researchers to distinguish the congestion losses from wireless channel losses, we compute RTT variation statistics under different kinds of simulation topologies such as high-speed wireless last hop, slow wireless backbone with both long router queue length and small queue length. The simulation results show that: (1)the average throughput of SACK and NewReno are slightly higher than those of Tahoe and Reno; (2)simple RTT variation schemes can not always predict congestion from wireless link error well. Moreover they do not work well under all kinds of simulation topologies and background load environments.