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Issue No. 05 - September/October (2005 vol. 4)
ISSN: 1536-1233
pp: 517-529
Sumitha Bhandarkar , IEEE Computer Society
A.L. Narasimha Reddy , IEEE Computer Society
Nitin H. Vaidya , IEEE Computer Society
This paper presents TCP-DCR, a set of simple modifications to the TCP protocol to improve its robustness to channel errors in wireless networks. TCP-DCR is based on the simple idea of allowing the link-level mechanism to recover the packets lost, due to channel errors, thereby limiting the response of the transport protocol to mostly congestion losses. This is done by delaying the triggering of congestion response algorithms for a small bounded period of time \tau to allow the link-level retransmissions to recover the loss due to channel errors. If at the end of the delay \tau the packet is not recovered, then it is treated as a packet lost due to congestion. We analyze TCP-DCR to show that the delay in congestion response does not impact the fairness towards the native implementations of TCP that respond to congestion immediately after receiving three dupacks. We evaluate TCP-DCR through simulations to show that it offers significantly better performance when channel errors contribute more towards packet losses in the network with no or minimal impact on the performance when congestion is the primary cause for packet loss. We also present an analysis to show that protocol evaluation in the wireless networks is significantly influenced by the number of flows in the network.
Index Terms- Wireless network, channel errors, TCP, delayed congestion response, local recovery.

S. Bhandarkar, N. H. Vaidya, N. E. Sadry and A. N. Reddy, "TCP-DCR: A Novel Protocol for Tolerating Wireless Channel Errors," in IEEE Transactions on Mobile Computing, vol. 4, no. , pp. 517-529, 2005.
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