TCP Vegas
Encyclopedia
TCP Vegas is a TCP 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 regarding 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 "flavors" of TCP congestion avoidance algorithms. 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 FreeBSD
, and several router firmware packages such as Tomato and DD-WRT
, and possibly other operating system
s as well.
TCP congestion avoidance algorithm
Transmission Control Protocol uses a network congestion avoidance algorithm that includes various aspects of an additive increase/multiplicative decrease scheme, with other schemes such as slow-start in order to achieve congestion avoidance....
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
University of Arizona
The University of Arizona is a land-grant and space-grant public institution of higher education and research located in Tucson, Arizona, United States. The University of Arizona was the first university in the state of Arizona, founded in 1885...
by Lawrence Brakmo
Lawrence Brakmo
Lawrence Brakmo is currently a member of technical staff at Google. Previously Brakmo was a researcher and project manager at NTT DoCoMo USA Labs. Before that he was affiliated with the Western Research Lab of Digital Equipment Corporation/Compaq/Hewlett-Packard. Brakmo received his Ph.D...
and Larry L. Peterson
Larry L. Peterson
Prof. Larry L. Peterson is a noted American computer scientist at Princeton University, in Princeton, New Jersey.Dr. Peterson received his B.S. in Computer Science from Kearney State College, Nebraska, in 1979, and M.S. and Ph.D. degrees in Computer Science from Purdue University in 1982 and 1985,...
.
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 regarding 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 "flavors" of TCP congestion avoidance algorithms. It is one of a series of efforts at TCP tuning
TCP tuning
TCP tuning techniques adjust the network congestion avoidance parameters of TCP connections over high-bandwidth, high-latency networks. Well-tuned networks can perform up to 10 times faster in some cases.- Bandwidth-delay product :...
that adapt congestion control and system behaviors to new challenges faced by increases in available bandwidth in Internet components on networks like Internet2
Internet2
Internet2 is an advanced not-for-profit US networking consortium led by members from the research and education communities, industry, and government....
.
TCP Vegas has been implemented in the Linux kernel
Linux kernel
The Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....
and FreeBSD
FreeBSD
FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
, and several router firmware packages such as Tomato and DD-WRT
DD-WRT
DD-WRT is a Linux-based firmware for several wireless routers, most notably the Linksys WRT54G . Like other similar projects, DD-WRT is third-party firmware designed to replace the firmware that ships pre-installed on many commercial routers...
, and possibly other operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s as well.
See also
- TCP congestion avoidance algorithmTCP congestion avoidance algorithmTransmission Control Protocol uses a network congestion avoidance algorithm that includes various aspects of an additive increase/multiplicative decrease scheme, with other schemes such as slow-start in order to achieve congestion avoidance....
- Development of TCP
External links
- University of ArizonaUniversity of ArizonaThe University of Arizona is a land-grant and space-grant public institution of higher education and research located in Tucson, Arizona, United States. The University of Arizona was the first university in the state of Arizona, founded in 1885...
- Advanced Protocol Design - Vegas.