H-TCP
Encyclopedia
H-TCP is another implementation of TCP
with an optimized congestion control algorithm for high speed networks with high latency (LFN: Long Fat Networks). It was created by researchers at the Hamilton Institute in Ireland.
H-TCP is an optional module in recent Linux
2.6 kernels.
algorithm, using additive-increase/multiplicative-decrease (AIMD) to control TCP's congestion window. It is one of many TCP congestion avoidance algorithms which seeks to increase the aggressiveness of TCP on high bandwidth-delay product (BDP) paths, while maintaining "TCP friendliness" for small BDP paths. H-TCP increases its aggressiveness (in particular, the rate of additive increase) as the time since the previous loss increases. This avoids the problem encountered by HSTCP
and BIC TCP
of making flows more aggressive if their windows are already large. Thus, new flows can be expected to converge to fairness faster under HTCP than HSTCP and BIC TCP.
. Techniques to overcome this are currently in the research phase.
The Linux implementation of H-TCP also has an option for avoiding "RTT
unfairness", which occurs in TCP Reno, but is a particular problem for most high speed variants of TCP (although not FAST TCP
).
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
with an optimized congestion control algorithm for high speed networks with high latency (LFN: Long Fat Networks). It was created by researchers at the Hamilton Institute in Ireland.
H-TCP is an optional module in recent Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
2.6 kernels.
Principles of operation
H-TCP is a loss-basedPacket loss
Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination. Packet loss is distinguished as one of the three main error types encountered in digital communications; the other two being bit error and spurious packets caused due to noise.-...
algorithm, using additive-increase/multiplicative-decrease (AIMD) to control TCP's congestion window. It is one of many TCP congestion avoidance algorithms which seeks to increase the aggressiveness of TCP on high bandwidth-delay product (BDP) paths, while maintaining "TCP friendliness" for small BDP paths. H-TCP increases its aggressiveness (in particular, the rate of additive increase) as the time since the previous loss increases. This avoids the problem encountered by HSTCP
HSTCP
HighSpeed TCP is a new congestion control algorithm protocol defined in RFC 3649 for TCP. Standard TCP performs poorly in networks with a large bandwidth delay product. It is unable to fully utilize available bandwidth...
and BIC TCP
BIC TCP
BIC TCP is an implementation of TCP with an optimized congestion control algorithm for high speed networks with high latency: so-called "long fat networks".BIC has a unique congestion window algorithm...
of making flows more aggressive if their windows are already large. Thus, new flows can be expected to converge to fairness faster under HTCP than HSTCP and BIC TCP.
Strengths and weaknesses
A side effect of increasing the rate of increase as the time since the last packet loss increases, is that flows which happen not to lose a packet when other flows do, can then take an unfair portion of the bandwidthBandwidth (computing)
In computer networking and computer science, bandwidth, network bandwidth, data bandwidth, or digital bandwidth is a measure of available or consumed data communication resources expressed in bits/second or multiples of it .Note that in textbooks on wireless communications, modem data transmission,...
. Techniques to overcome this are currently in the research phase.
The Linux implementation of H-TCP also has an option for avoiding "RTT
Round-trip delay time
In telecommunications, the round-trip delay time or round-trip time is the length of time it takes for a signal to be sent plus the length of time it takes for an acknowledgment of that signal to be received...
unfairness", which occurs in TCP Reno, but is a particular problem for most high speed variants of TCP (although not FAST TCP
FAST TCP
FAST TCP is a TCP congestion avoidance algorithm especially targeted at long-distance, high latency links, developed at the , California Institute of Technology and now being commercialized by...
).
Name
The algorithm was initially introduced as H-TCP, without mention of what the 'H' stands for. However, it is often called "Hamilton TCP", for the Hamilton Institute where it was created.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....
- Transmission Control Protocol#Development of TCP