Momentary Recovery Algorithm: A New Look at the Traditional Problem of TCP

Jae-Hyun HWANG  See-Hwan YOO  Chuck YOO  

IEICE TRANSACTIONS on Communications   Vol.E92-B   No.12   pp.3765-3773
Publication Date: 2009/12/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E92.B.3765
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Network
transmission control protocol,  loss recovery algorithm,  congestion control,  recovery overhead,  

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Traditional TCP has a good congestion control strategy that adapts its sending rate in accordance with network congestion. In addition, a fast recovery algorithm can help TCP achieve better throughput by responding to temporary network congestion well. However, if multiple packet losses occur, the time to enter congestion avoidance phase would be delayed due to the long recovery time. Moreover, during the recovery phase, TCP freezes congestion window size until all lost packets are recovered, and this can make recovery time much longer resulting in performance degradation. To mitigate such recovery overhead, we propose Momentary recovery algorithm that recovers packet loss without an extra recovery phase. As other TCP and variants, our algorithm also halves the congestion window size when packet drop is detected, but it performs congestion avoidance phase immediately as if loss recovery is completed. For lost packets, TCP sender transmits them along with normal packets as long as congestion window permits rather than performs fast retransmission. In this manner, we can eliminate recovery overhead efficiently and reach steady state momentarily after network congestion. Finally, we provide a simulation based study on TCP recovery behaviors and confirm that our Momentary recovery algorithm always shows better performance compared with NewReno, SACK, and FACK.