Pragmatic Router Fib Caching

Several recent studies have shown that router FIB caching offers excellent hit rates with cache sizes that are an order of magnitude smaller than the original forwarding table. However, hit rate alone is not sufficient - other performance metrics such as memory accesses, robustness to cache attacks, queuing delays from cache misses etc., should be considered before declaring FIB caching viable.In this paper, we tackle several pragmatic questions about FIB caching. We characterize cache performance in terms of memory accesses and delay due to cache misses. We study cache robustness to pollution attacks and show that an attacker must sustain packet rates higher than the link capacity to evict the most popular prefixes. We show that caching was robust, even during a recent flare of NTP attacks. We carry out a longitudinal study of cache hit rates over four years and show the hit rate is unchanged over that duration. We characterize cache misses to determine which services are impacted by FIB caching. We conclude that FIB caching is viable by several metrics, not just impressive hit rates.