Two Dimensional Router: Design and Implementation

Packet classification has attracted research attentions along with the increasing demands for more flexible services in the Internet today. Among different design approaches, hardware based classification is attractive as it can achieve very fast performance. We present our design and implementation of a two dimensional router (TwoD router). It makes forwarding decisions, in hardware level, based on both destination and source addresses. This can fundamentally increase routing semantics to support services beyond destination-based routing. Our TwoD router is also motivated by our effort towards developing two dimensional IP routing. With one more dimension, the forwarding table grows explosively. Theoretically, the storage footprint increases from O(N) (the number of destination prefixes) to O(N2). It is no longer possible to fit such forwarding table into TCAM, the de facto router standard. In this paper, we propose a new forwarding table structure through a neat separation of TCAM and SRAM where we harvest the speed of TCAM and the storage/flexibility of SRAM. Under this structure, we first develop schemes to maintain forwarding correctness. We then develop algorithms to further compress TCAM and SRAM storage. With a pipelining scheme, we show that the lookup speed of our TwoD router is the same to the conventional routers. We also develop algorithms that minimize memory rewrites during update operations. We evaluate our design with an implementation on a commercial router, Bit-Engine 12004, using real data sets to support two practical services, policy routing and load balancing of CERNET2. Our design does not need new hardware. The evaluation results show that our TwoD router can be practical for ISPs like CERNET2.