Chapter 4 - IP Routing

Abstract

This chapter focuses on the fundamental aspects of the link state protocols, which include the reliable network topology discovery mechanism, the distributed shortest path computation, and the routing table calculation. The chapter reviews the dynamic aspects of the distributed routing and delineates the various steps occurring during the network convergence. Running a routing protocol is done for each node to build a routing table that contains the shortest path to each reachable Internet protocol (IP) prefix. The entire path does not have to be stored to route the packet, instead, the router maintains a data structure called the forwarding information base (FIB) that contains the next hop for each reachable IP prefix along with other protocol information. There are several routing protocols, which can be divided into two categories—the distance vector routing protocols and the link state routing protocols. Different failure profiles can occur in an IP/Multi-Protocol Label Switching (MPLS) network. There are two families of failure detection mechanisms that can be used to detect such failures and their respective performance and scalability—the lower layers failure notification and the hello-based mechanisms.