Incremental update procedure for IP lookup tables

Abstract

In the basic operation of a network, an IP router plays an important role for transferring packets. When a packet arrives, the router has to look up the longest matching prefix in a routing table and forward the packet to the corresponding next-hop. When a router is switched off for maintenance, there will be some information packets transferring between other routers for updating the routing table. A router may receive several million packets per second from each input link. Thus a high speed IP prefix matching process is required. Bit shuffling is a suggested method to handle the IP look up problem. This project investigates the update procedure and evaluates the internal and external memory update cost in updating a routing table under the bit shuffling method. It focuses on the prefixes with length 21-24 bits. The memory update cost of a prefix considers as the numbers of memory access required for inserting or deleting a prefix. For the on-chip memory, 99% of memory access is below 17 and the maximum one is 53. For the off-chip memory, 98% of memory access is below 15. The memory update cost must be an odd number and below 29.