Abstract : As a key component of high-performance switches and routers, the Packet Forwarding Engine (PFE) is mainly responsible for selecting the appropriate output port for tens of thousands of packets within an extremely short time frame. And the performance of PFE is determined by the group membership algorithm. In this paper, we put forth a hybrid strategy–Caching Scalar-pair and Vectors Routing and Forwarding (CSVRF), consisting of Virtual Output Port Bitmap Caching (VOPBC) and Fractional-N SVRF to address major multicast forwarding issues such as scalability, which is implemented by using Content Address Memory (CAM). In CSVRF, we first introduce a virtual output port bitmap cache table, which includes the most popular combinations of output port bitmap (OPB), and divides the big scalar-pair into N sub-groups to achieve the reusability of prime. The results demonstrate that the memory space and the forwarding latency are effectively reduced. In memory space, we only required 10% memory space compared with the original SVRF demands, and also decrease 10% memory usage compared with pure VOPBC. And we only occupy nearly 1‱ and 5% packet processing time compared with the original SVRF and the Fractional-N SVRF in high port-density (like 1024 ports) respectively. We proved our conclusions by mathematical models and simulations via Matlab, respectively. We believe that our scheme not only effectively reduces the less memory usage and processing time but also has good scalability in high port-densities.
Index terms : Multicast, Packet Forwarding Engine, Membership Querying, Routing and Forwarding