Study On Congestion Control Of Multi-homing System

Emerging cloud computing, Internet of Things, and a large number of critical emergency services urgently need high throughput rates and multiple access standard provided by the next generation Internet, which is sufficient to withstand network failure, improve the ability to quickly recover and avoid huge economic losses due to temporary Service Interruption. The multipath concurrent transmission of multi-homing terminal equipment, with multiple ISP redundant connection can guarantee the key service availability. Multipath transmission protocol MPTCP and CMT-SCTP protocol are just the implementation of next generation Internet multi-homed system protocol, and the focus of current international IETF organization.The conventional single-path congestion control mechanism cannot meet the needs of multi-path transmission protocol, and multipath transmission protocol congestion control will face problems, such as fairness. This thesis firstly introduced the classification of the existing multi-path transmission technology, explained the reasons of the generating of network congestion.Then the thesis reviewed the traditional TCP and SCTP congestion control algorithm, raising the unfairness problem of Multipath concurrent transmission, introduced the congestion control algorithm based on the ideas of resource pooling. The new algorithms make every congestion window of sub-flow is coupled between the proportional change, by using factor considered global. So as to improve throughput, achieve fairness and balance congestion.To verify the validity of multi-homed system protocol congestion control, we designed two tests in the local and international test bed named NorNert. The local test especially for the three new algorithms based on the resource pooling, sets up the Bottleneck Scenario and Disjoint Paths Scenario. And got the following conclusions:the multipath congestion control mechanisms based on the resource pooling is a better solution to the general fairness and TCP-Friendliness in two scenarios, CMT/RPvl CC is only suitable for similar paths; MPTCP-like CC and CMT/RPv2CC have wider applicability and can apply to cope with dissimilar paths. The test in NorNet mainly aiming at congestion control of MPTCP, builds two-site scenario crossing Asia and Europe and three-site scenario across Americas, Asia and Europe. The results show that:When no bottleneck, there is no essential difference among Cubic, Lia and Reno in single-path and multi-path transmission;In Individual Cases, Cubic is better than Lia and Reno; When regarding the low-speed ISP as the sender, concurrent multi-path transmission significantly enhances Received Bit Rate and balances congestion; When regarding the high-speed ISP as the sender, Received Bit Rate does not change much, it meets the fairness principle of congestion control mechanisms, that is, without affecting other users of resources.