Study On Congestion Controls In Background Transport Network

Conventional Transmission Control Protocol (TCP) is a connection-oriented reliable transport layer protocol, which is widely used to transmit files and e-mails. TCP flows usually keep increasing congestion windows until packets lose. But many time-insensitive applications like software update and files sharing tend to use idle capacity in the network, rather than disturbing interactive services. Such applications can use background congestion controls which have lower priority than standard TCP.This paper mainly discusses several common delay-based congestion controls for background transport network, such as TCP Nice, TCP Low Priority and Low Extra Delay Background Transport (LEDBAT). Among them, the author focuses on the new congestion control LEDBAT. Based on LEDBAT, this paper proposes a new background congestion control named as G-linked TCP. G-linked TCP associates sending window gain G with queuing delay to fasten the sending rate, and properly descends sending window to achieve fairness between intra-protocol flows. Evaluation results show that, in given scenario, G-linked TCP spends much shorter time than other congestion controls to utilize the link capacity. Meanwhile, G-linked TCP keeps low priority to common TCP traffic like TCP Reno, Compound TCP and CUBIC. Besides, G-linked TCP effectively resolves the unfairness problem "latecomer advantage", enhancing the Jain fairness index close to1even with different network settings. These characteristics make G-linked TCP qualified as a background traffic control for Internet.