TCP Vegas

TCP Vegas is a TCP congestion control, or network congestion avoidance, algorithm that emphasizes packet delay, rather than packet loss, as a signal to help determine the rate at which to send packets. It was developed at the University of Arizona by Lawrence Brakmo and Larry L. Peterson.

TCP Vegas detects congestion at an incipient stage based on increasing Round Trip Time (RTT) values of the packets in the connection unlike other flavors like Reno, NewReno etc. which detect congestion only after it has actually happened via packet drops. The algorithm depends heavily on accurate calculation of the Base RTT value. If it is too small then throughput of the connection will be less than the bandwidth available while if the value is too large then it will overrun the connection. A lot of research is going on the fairness provided by the linear increase/decrease mechanism for congestion control in Vegas. One interesting caveat is when Vegas is inter-operated with other versions like Reno. In this case, performance of Vegas degrades because Vegas reduces its sending rate before Reno as it detects congestion early and hence gives greater bandwidth to co-existing TCP Reno flows.

TCP Vegas is one of several varieties of TCP congestion avoidance algorithm. It is one of a series of efforts at TCP tuning that adapt congestion control and system behaviors to new challenges faced by increases in available bandwidth in Internet components on networks like Internet2.

TCP Vegas has been implemented in the Linux kernel and possibly other operating systems also.