Broadband Packet Switching Technologies: A Practical Guide to ATM Switches and IP Routers

CHAPTER 13

IP ROUTE LOOKUPS

The emergence of new multimedia networking applications and the growth of the Internet due to the exponentially increasing number of users, hosts, and domains have led to a situation where network capacity is becoming a scarce resource. In order to maintain the good service, three key factors have been considered in designing IP networks: large-bandwidth links, high router data throughput, and high packet forwarding rates [16]. With the advent of fiber optics, which provides fast links, and the current switching technology, which is applied for moving packets from the input interface of a router to the corresponding output interface at gigabit speeds, the first two factors can be readily handled. Therefore, the key to the success of the next generation IP networks is the deployment of high-performance routers to forward the packets at the high speeds.

There are many tasks to be performed in packet forwarding; packet header encapsulation and decapsulation, updating a time-to-live (TTL) field in each packet header, classifying the packets into queues for specific service classes, etc. The major task, which seems to dominate the processing time of the incoming packet, is searching for the next-hop information of the appropriate prefix matching the destination ...