Saturday, October 2, 2010

Will TCP Vegas ever be Used?

TCP Vegas is a flavor of TCP that uses round-trip time estimates, rather than loss detection to adjust sending rates. Vegas came out at the time when TCP Reno was prevalent in the Internet, and it offered performance advantages over Reno. The inventors of Vegas discovered a 40-70% throughput increase, as well as up to one-half the loss of TCP Reno.

While the Vegas algorithm seemed like a promising alternative, it received some criticism by experts, including Van Jacobson, the inventor of the original TCP's congestion-control mechanism. Jacobson argued that Vegas violates the flow model, and that the Internet could not support Vegas. Also, Vegas was originally thought to perform worse when competing with Reno flows. And since Vegas was invented, newer versions such as NewReno and SACK TCP have emerged since then that have higher throughput and less loss.

It makes me wonder if Vegas outperforms the newer versions of TCP. If it works better than SACK TCP, and can be built to follow the flow model, then it may be still be advantageous to use TCP Vegas.

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