高效的Crossbar仲裁算法——ISP

ISP: A High Performance Crossbar Arbitrating Algorithm

交换开关是高性能路由器的核心 .目前高性能骨干路由器一般采用基于输入队列的 crossbar交换开关 .高效的 crossbar仲裁算法对路由器设计十分重要 .文中提出一种轮询与 Round Robin相结合的仲裁算法—— ISP(Input Serial Polling) .轻负载时 ISP算法与 i SL IP算法性能相当 ,重负载时 ISP算法在带宽利用率、信元平均延时和公平性等方面优于 i SL IP算法 .ISP算法实现简单 ,用可编程逻辑器件实现的 16端口 ISP仲裁器工作频率可达65 MHz,一次仲裁时间小于 2 5 0 ns,因此 ISP仲裁器可用于高性能的骨干路由器中 .

Switch is very important to a high performance router. Today's high performance core routers always use input queue based crossbar switches. A high performance crossbar arbitrating algorithm is very important to the router design. This paper presents a combined polling and round robin algorithm, Input Serial Polling(ISP). ISP has almost the same performance with iSLIP algorithm when the load is low, but when the load is very high, ISP can achieve higher throughput, shorter cell delay and better equity than iSLIP. ISP algorithm is simple. Sixteen port ISP arbiter can be implemented by programmable logic, with working frequency as high as 65MHz. it can complete one arbitration within 250ns, so it can be used in high performance core routers.