CAMP: Fast and efficient IP lookup architecture

A large body of research literature has focused on improving the performance of longest prefix match IP-lookup. More recently, embedded memory based architectures have been proposed, which delivers very high lookup and update throughput. These architectures often use a pipeline of embedded memories, where each stage stores a single or set of levels of the lookup trie. A stream of lookup requests are issued into the pipeline, one every cycle, in order to achieve high throughput. Most recently, Baboescu et al. [21] have proposed a novel architecture, which uses circular memory pipeline and dynamically maps parts of the lookup trie to different stages. In this paper we extend this approach with an architecture called Circular, Adaptive and Monotonic Pipeline (CAMP), which is based upon the key observation that circular pipeline allows decoupling the number of pipeline stages from the number of levels in the trie. This provides much more flexibility in mapping nodes of the lookup trie to the stages. The flexibility, in turn, improves the memory utilization and also reduces the total memory and power consumption. The flexibility comes at a cost however; since the requests are issued at an arbitrary stage, they may get blocked if their entry stage is busy. In an extreme case, a request may block for a time equal to the pipeline depth, which may severely affect the pipeline utilization. We show that fairly straightforward techniques can ensure nearly full utilization of the pipeline. These techniques, coupled with an adaptive mapping of trie nodes to the circular pipeline, create a pipelined architecture which can operate at high rates irrespective of the trie size.