核心路由器转发引擎缓存需求分析

An Analysis of Memory Demand for Forwarding Engines in Core Routers

路由器是一种存储转发设备,其缓存设置的大小直接影响路由器的性能,进而还会影响整个网络的性能.本文针对路由器核心部件—转发引擎的缓存需求进行分析.首先,将流水线技术引入转发引擎设计中,提出了一条转发引擎流水线,然后分转发引擎处理能力不小于、小于外部输入速率两种情况对转发引擎缓存需求进行了分析.分析结果和实验表明:当处理能力不小于外部输入速率时,几个最长包的缓存便能满足转发引擎的缓存需求,当处理能力小于外部输入速率时,从缓存的使用效率来看,小数量缓存(10个包左右的缓存)仍然是一个合理的选择,更大的缓存对丢包率的降低作用并不明显.

All intemet touters contain buffers to store packets. Selecting appropriate buffer size can not only ensure router performance, but can also contribute to reducing uncertainty in the intemet. This paper aims to size buffers for forwarding engines known as the main part of a muter. First, a high-speed pipeline which is designed for forwarding engines is presented, and its memory analysis model is also given, then,the memory demand of forwarding engines is analyzed under two situations：the forwarding capability being not less than and less than the input rate. Our analysis results and experiments both show that, when the forwarding capability is not less than the input rate,a forwarding engine only need to buffer a several packets of maximum length, when the forwarding capability is less than the input rate, a forwarding engine only needs to buffer about ten packets in the view of buffer use efficiency, and further increasing the buffer size will have little effect.