Ternary Content-Addressable Memory (TCAM) chips are used to store Forwarding Information Bases (FIB) in modern routers. TCAM provides next-hop lookup for IP packets at the line-rate. However, TCAM is expensive and energy-consuming; in addition, the constant FIB growth may lead to TCAM overflow problem. Yet only a small portion of FIB entries carries the most of network traffic. Thus, FIB caching, namely, installing the most popular entries in a fast memory, e.g., TCAM, may significantly minimize TCAM usage. To date, FIB caching architecture has not been widely deployed in backbone routers due to high cache-miss latency and the lack of an efficient cache replacement strategy. In this work, we leverage the concept of the programmable data plane to design a Programmable FIB Caching Architecture (PFCA) with two levels of cache. We present a pipeline-based algorithm to detect the least popular prefixes in a cache for a victim selection. We tested the prototype of PFCA using real traffic traces and an FIB with more than 599K entries, and showed that PFCA can be implemented using P4 programmable data plane language. Our results show that PFCA achieves 99.8% hit ratio for Level-1 cache with 20K entries and nearly 99.9% hit ratio for Level-2 cache with 40K entries. We also demonstrate that PFCA significantly reduces the number of BGP updates in the cache and thus makes the cache more stable.

中文翻译：

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PFCA：可编程的FIB缓存体系结构

三元内容可寻址存储器（TCAM）芯片用于在现代路由器中存储转发信息库（FIB）。TCAM以线速为IP数据包提供下一跳查找。但是，TCAM昂贵且耗能。此外，FIB的持续增长可能会导致TCAM溢出问题。但是，FIB条目中只有一小部分承载了大部分网络流量。因此，FIB缓存，即在快速存储器（例如TCAM）中安装最流行的条目，可能会大大减少TCAM的使用。迄今为止，由于高缓存丢失延迟和缺乏有效的缓存替换策略，FIB缓存体系结构尚未在骨干路由器中广泛部署。在这项工作中，我们利用可编程数据平面的概念来设计具有两级缓存的可编程FIB缓存体系结构（PFCA）。我们提出了一种基于管道的算法来检测缓存中用于受害者选择的最不流行的前缀。我们使用实际流量跟踪和具有超过599K条目的FIB测试了PFCA的原型，并表明PFCA可以使用P4可编程数据平面语言来实现。我们的结果表明，PFCA对于具有2万个条目的Level-1缓存达到了99.8％的命中率，对于具有4万个条目的Level-2缓存达到了99.9％的命中率。我们还证明了PFCA大大减少了缓存中BGP更新的数量，从而使缓存更加稳定。我们的结果表明，PFCA对于具有2万个条目的Level-1缓存达到了99.8％的命中率，对于具有4万个条目的Level-2缓存达到了99.9％的命中率。我们还证明了PFCA大大减少了缓存中BGP更新的数量，从而使缓存更加稳定。我们的结果表明，PFCA对于具有2万个条目的Level-1缓存达到了99.8％的命中率，对于具有4万个条目的Level-2缓存达到了99.9％的命中率。我们还证明了PFCA大大减少了缓存中BGP更新的数量，从而使缓存更加稳定。