Investigations On TCP Friendly Congestion Control

With the vast development of the technology of media and network,,the multimedia streaming applications including Picture phone, Long-distance education and Video conference have become the main operations in the internet. But Internet can't provide a good environment for this development. In existing environment, the multimedia data are always lost or have long delay which led to a serious quality problem. The network researchers have found out the reason is that the existing transport protocol doesn't have an effective congestion control for multimedia streaming applications. So, the data streaming can't fit the requirement of multimedia transport and can't use the bandwidth fairly with other streaming especially the TCP data streaming. In order to solve this problem of multimedia streaming applications, the TCP friendly congestion control has been brought forward and it becomes a hot point of network protocol research.We have known that TFRC is very good after comparing the current TCP friendly congestion control mechanisms. Using loss event rate to judge the congestion state of the network in TFRC can solve the problem of other mechanisms. Its sending rate is smoother because it doesn't cut down the rate half when one packet has dropped. In addition, TFRC uses the TCP throughput equation to adjust sending rate, so it can share the bandwidth fairly with TCP data streaming. Even if TFRC is very good, it has a problem. There is a low sending rate threshold to guarantee the playback quality when translating multimedia streaming. However, TFRC can't satisfy it and make useless transport when congestion happens. So, TC-TFRC as an improvement of TFRC has been proposed. This mechanism forces streaming media to use a low sending rate when congestion happens and keeps the TCP friendliness by using"sufferable transient timer"to limit the time source sending rate with the low sending rate. The results of simulation show that TC-TFRC can solve the problem of TFRC.Through our further research we find that there are shortcoming of"sufferable transient timer"and the way in which TC-TFRC adjust its sending rate. TC-TFRC sources send too much data beyond the tolerance of Internet when the congestion is...