Authors: H. Balakrishnan, S. Seshan, and R.H. Katz
Date: 1995
TCP is a reliable transport protocol tuned to perform well in
traditional networks where congestion is the primary cause of
packet loss. However, networks with wireless links and mobile
hosts incur significant losses due to bit-errors and handoffs.
This environment violates many of the assumptions made by TCP,
causing degraded end-to-end performance. The authors describe
the additions and modifications to the standard Internet
protocol stack (TCP/IP) to improve end-to-end reliable
transport performance in mobile environments. The protocol
changes are made to network-layer software at the base station
and mobile host, and preserve the end-to-end semantics of TCP.
One part of the modifications, called the snoop module, caches
packets at the base station and performs local retransmissions
across the wireless link to alleviate the problems caused by
high bit-error rates. The second part is a routing protocol
that enables low-latency handoff to occur with negligible data
loss. The authors have implemented this new protocol stack on
a wireless testbed. The experiments show that this system is
significantly more robust at dealing with unreliable wireless
links than normal TCP; the authors have achieved throughput
speedups of up to 20 times over regular TCP and handoff
latencies over 10 times shorter than other mobile routing
protocols.