Who am I Competing Against?: Identifying Adversarial Protocols Against TCP in a Congested Link

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• Idris Rai, Makerere University, Uganda
• Thursday 16 July 2009, 14:00-15:00
• SS03, William Gates Building.

If you have a question about this talk, please contact Andrew Rice.

Classical TCP designs have never considered the identity of the competing transport protocol as useful information to TCP sources in congestion control mechanisms. When competing against a TCP flow on a bottleneck link, a UDP flow can unfairly occupy the entire link bandwidth and suffocate all TCP flows on the link. If it were possible for a TCP source to know the type of the flow that deprives it of link access, perhaps it would be better for the TCP source to react in a way that it avoids starvation.

In this talk we use coefficient of variation and power spectral density of throughput traces to identify the presence of UDP transport protocols that competes against a TCP flow on a bottleneck link. Our results show clear traits that differentiate the presence of competing UDP flows from TCP flows independent of round trip times variations. Signatures that we identified include an increase in coefficient of variation whenever a competing UDP flow joins the bottleneck link for the first time, noisy spectral density representation of a TCP flow when competing against a UDP flow in the bottleneck link, and a dominant frequency with outstanding power in the presence of TCP competition only. In addition, the results show that signatures for congestion caused by competing UDP flows are different from signatures due to congestion caused by competing TCP flows of regardless their round trip times. The results in this paper present the first steps towards development of more ’intelligent’ congestion control algorithms with added capability of knowing the identity of aggressor protocols against TCP , and subsequently using this additional information for rate control.

This talk is part of the Computer Laboratory Digital Technology Group (DTG) Meetings series.

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