Discriminating Congestion Losses from Wireless Losses using Inter-Arrival Times at the Receiver

• Authors: Saad Biaz;Nitin H. Vaidya
• Venue: Discriminating Congestion Losses from Wireless Losses using Inter-Arrival Times at the Receiver
• Year: 1998

TCP has been designed and tuned to perform well under the assumption that all losses are an indication of congestion. When a TCP connection traverses a wireless link, packets may be lost due to wireless transmission errors, in addition to congestion losses. TCP implicitly assumes that all packet losses are due to congestion, and triggers congestion control mechanism when a packet loss is detected. It has been previously demonstrated that this feature of TCP affects performance adversely when packets are lost due to transmission errors. To avoid the performance degradation, techniques to distinguish between corruption and congestion losses without any explicit information from the network (routers or switches) are of interest. The objective of this paper is to present a simple scheme which can be implemented at the receiver to distinguish congestion losses from corruption losses. The scheme works in the case where the last hop to the receiver is a wireless link and has the smallest bandwidth among all links on the connection path. With such mechanism, the receiver can attempt to detect the real cause of the packet loss and inform the TCP sender to take the appropriate actions. Specifically, if the loss is a transmission error, the receiver can speed up the recovery and avoid shrinkage of sender''s congestion window. We added our mechanism to TCP-Reno to evaluate the performance improvement. We compared our scheme against Ideal TCP-Reno which is TCP-Reno that can perfectly (but artificially) distinguish between congestion losses and wireless transmission losses. Under favorable conditions, our scheme performs similarly to Ideal TCP-Reno and can lead to significative throughput improvement.