Efficient FIB caching using minimal non-overlapping prefixes

Abstract

The size of the global Routing Information Base (RIB) has been increasing at an alarming rate. This directly leads to the rapid growth of the global Forwarding Information Base (FIB) size, which raises serious concerns for ISPs as the FIB memory in line cards is much more expensive than regular memory modules and it is very costly to increase this memory capacity frequently for all the routers in an ISP. One potential solution is to install only the most popular FIB entries into the fast memory (i.e., a FIB cache), while storing the complete FIB in slow memory. In this paper, we propose an effective FIB caching scheme that achieves a considerably higher hit ratio than previous approaches while preventing the cache-hiding problem. Our experimental results show that with only 20K prefixes in the cache (5.36% of the actual FIB size), the hit ratio of our scheme is higher than 99.95%. Our scheme can also handle cache misses, cache replacement and routing updates efficiently.