Go-to-Controller is Better: Efficient and Optimal LPM Caching with Splicing

Data center networks must support huge forwarding policies as they handle the traffic of the various tenants. Since such policies cannot be stored within the limited memory available at commodity switches, SDN controllers can manage the memory available at the switch as a cache, updating and changing the forwarding rules in the cache according to the policy and workloads dynamics. Most policies, such as Longest-prefix-match (LPM) policies, include dependencies between the forwarding rules, which introduce consistency constraints on the structure of the cached content, affecting the performance in terms of throughput and delay. Previous work suggested the concept of splicing to address such deficiencies, where modified Go-to-Controller rules can be inserted into the cache to improve performance while maintaining consistency. We present the first optimal algorithm for determining the cache content with splicing, as well as several efficient heuristics with some performance guarantees. We evaluate our solutions using traces derived from real systems and traffic, and show that splicing can reduce the cache miss ratio by as much as 30%, without increasing the cache size. We further propose a new metric which can provide a quick estimate as to the potential benefits of splicing compared to classical LPM-caching. The full version of our work appeared in [2].