OpenFlow交换机动态共享限速机制的研究

A Mechanism of Dynamic Meter Sharing on OpenFlow Switch

每流限速一直以来都是互联网服务质量保障(QoS)的一大挑战,由于受到硬件资源的限制,很难找到一种快速高效的算法在数据包级对流量进行区分限速.OpenFlow1.3协议对每流限速(Meter)部分,给出了具体定义和描述,该文参照该协议标准,提出了具体的Meter实现方案,并在ONetSwitch硬件平台上,进行了实验验证和性能测试.本文通过对网络流量的统计分析,发现网络中共存的流数量往往只占总流量的万分之一,因此使多条流分时共享硬件资源,可以有效解决每流限速的难题.参考动态队列共享(DQS)的思想,该文提出动态共享限速(DMS)算法,在多条流之间进行调度,实现多条流分时共享限速通道,在硬件资源受限,限速通道数量一定,同时需要限速的流数量大于限速通道数量时,能够有效地实现对各条流进行限速的功能.实验结果表明,Meter能够为每条流有效分配限速通道,从而在网络中对多条流以不同的速率区分限速.

Per-flow rate-limiting is one of quality of the service（QoS）challenge in networking system.It is difficult to find a method that is both quick and efficient to manage flows which need to be limited to different rates due to the limitation of hardware resources.However,in OpenFlow-1.3specification,the Meter part describes the definition of per-flow rate limiting.According to the description of Meter,this paper provides a detailed implementation of Meter based on ONetSwitch hardware platform and verifies the performance through multiple groups of experiment.Through the statistic of flows in network,there are only 100 active flows in million network in-progress flows.Therefore,the per-flow rate limiting problem may be resolved through multiple flows time sharing hardware resources.Referencing the idea of Dynamic Queue Sharing（DQS）,Dynamic Meter Sharing（DMS）was proposed in this paper to schedule among different flows that sharing the same rate limiting pipe,but during different period.However,the number of rate limiters is limited due to the limitation of hardware resources.When flow numbers exceed the number of rate limiters,it is unavoidable to allocate some flows to a shared rate limiter waiting for idle ones.Although the critical＂per-flow rate limiting＂is not achieved,Meter has an advantage over traditional rate limiting method.The results show that Meter allocate an independent rate limiter for per-flow,then realize limiting multiple flows in different rate.