TCP is a reliable transport protocol tuned to perform well intraditional networks made up of links with low bit-error rates.Networks with higher bit-error rates, such as those with wirelesslinks and mobile hosts, violate many of the assumptions made byTCP, causing degraded end-to-end performance. In tbis paper, wedescribe the design and implementation of a simple protocol, calledthe snoop protocol, that improves TCP performance in wirelessnetworks. The protocol modifies network-layer software mainly at abase station and preserves end-to-end TCP semantics. The main ideaof the protocol is to cache packets at the base station and performlocal retransmissions across the wireless link. We have implementedthe snoop protocol on a wireless testbed consisting of IBM ThinkPadlaptops and i486 base stations communicating over an AT&TWavelan. Our experiments show that it is significantly more robustat dealing with unreliable wireless links as compared to normalTCP; we have achieved throughput speedups of up to 20 times overregular TCP in our experiments with the protocol.