一种改进的用于TCP/IP的后向显式拥塞指示算法

Revised Backward Explicit Congestion Notification Algorithm for TCP/IP

显式拥塞指示(ECN)和路由器中的主动队列管理(AQM)的结合运用,提高了TCP/IP协议对拥塞控制的能力。其中,后向显式拥塞指示(BECN)建议拥塞的路由器直接把拥塞信息通过ISQ返回给发送端,以减少对拥塞的反应时间。但是,BECN对拥塞窗口的减小程度不足,每收到一个ISQ包BECN的拥塞窗口仅减少1,严重影响到拥塞解除的性能。提出用乘性减少代替线性减少以增强BECN的性能,即每收到一个ISQ包拥塞窗口乘以一个小于1的系数。仿真结果表明,乘性减少BECN比线性减少BECN在性能上有显著的提高。

The combination of explicit congestion notification （ECN） and active queue management in routers （AQM） was introduced to improve the performance of congestion control in TCP/IP. Backward ECN （BECN） suggests a congested router to directly return the congestion information to the sender through ICMP source quench （ISQ） messages to reduce the reaction time to congestion. But, in BECN the shrinking degree to the congestion window is insufficient by reducing only one for each arrival of an ISQ packet, which effects the congestion release efficiency. This study proposes that linear decrease （LD） is replaced by multiplicative decrease （MD）, i.e., the congestion window is multiplied by a fraction less than 1. The simulation result shows that BECN/MD outperforms BECN/LD remarkably.