A Forwarding Approach for Routers Supporting PIM-SM in the IPv6 Networks

Protocol independent multicast-sparse mode can use either a shared tree or a shortest path tree to deliver IPv6 multicast packets, consequently the multicast IP lookup engine requires, in some cases, two searches to get a correct forwarding decision, and this will lead to a new requirement of doubling the lookup speed. The ordinary method to satisfy this requirement in TCAM-based (ternary content addressable memory) lookup engines is to exploit parallelism among multiple TCAMs, however, parallel methods always incur more resources and higher design difficulty. We propose in this paper a approach to solve this problem. By arranging multicast forwarding table in class sequence in TCAM together with using the intrinsic characteristic of the TCAM, our approach can use just one search and a single TCAM to get the right lookup result, while keeping the hardware of lookup engine unchanged. Experimental results have shown that the approach can make it possible for just one TCAM to satisfy forwarding IPv6 multicast packets at the full link rate of 20 Gb/s with the current TCAM chip level.