TCP Vegas重选路问题及其解决方法

A Rerouting Issue with TCP Vegas and its Solution

为克服传统Vegas机制在网络层重选路后可能出现的吞吐量劣化问题,提出了一种称为“主动激励”的新机制。该机制的基本思想是:当TCP拥塞窗口(cwnd)稳定在某个平衡点上时,源端主动地增加基准往返时延,以打破这种平衡,激励Vegas进行窗口调整,通过Vegas自身的窗口调整机制使cwnd达到一个新的平衡,进而对Vegas连接的吞吐量进行有效的恢复。“主动激励”机制并不修改Vegas算法且开销很小,可作为一个独立模块内嵌到Vegas或其增强算法中,从而可以容易地对这些算法进行扩充。

To overcome the problem of original Vegas scheme which probably brings forth the throughput degradation after rerouting operations, we propose a novel mechanism called ＂active spurring＂, whose basic idea is that the source actively increases the BaseRTT to break down the equilibrium when the congestion window（cwnd） is stabilized to some equilibrium, and then Vegas is spurred to adjust the cwnd to be stabilized to a new equilibrium by the basic window adjustment mechanism in Vegas, effectively restoring the throughput of Vegas connections accordingly. ＂Active spurring＂does not modify Vegas and can be simply embedded into the TCP Vegas or enhanced TCP Vegas as an independent module with a low overhead and hence be extended easily.