Performance Evaluation of TCP/IP in 802.11 Wireless Networks

B.C. Dhinakaran, D. Nagamalai, and L.S. Gap (Korea)


Snoop protocol, Congestion protocol, Handoff, Selective acknowledgments (SACK)


The increasing popularity of wireless networks indicates that wireless links will play an important role in future internetworks. TCP is a reliable transport protocol tuned to perform well in habitual networks made up of links with low bit-error rates. TCP was originally designed for wired networks, where loss of data is assumed to be due to congestion. However, networks with wireless and other lossy links also suffer from significant losses due to high bit error rates and handoff. But the assumption made by TCP, that loss of data is due to congestion in wireless environment causes degraded end-to-end performance. Hence a variety of mechanisms were proposed to improve TCP performance over wireless links. In this paper we wish to analyze the design and implementation of a simple protocol, called the snoop protocol that improves the performance of TCP in wireless networks. The protocol modifies the network layer software mainly at the base station and preserves end-to end TCP semantics. The main feature of this protocol is to cache packets at the base station and to perform local retransmission across the wireless links. The results of several experiments performed by implementing snoop protocol on a wireless test bed consisting of IBM think pads laptops and Pentium based personal computer running BSD/OS 2.1 from BSDI show that a reliable link layer protocol that is TCP-aware provides very good performance.

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