Network Routing

6Interior Gateway Protocols

• 6.1 Introduction
• 6.2 Distance Vector Protocols
  • 6.2.1 Routing Information Protocol
  • 6.2.2 Interior Gateway Routing Protocol
• 6.3 Link State Protocols
  • 6.3.1 Open Shortest Path First Protocol
  • 6.3.2 Intermediate System to Intermediate System Protocol
• References
• Abbreviations/Terminologies
• Questions
• Exercises

6.1 Introduction

A network is termed an autonomous system (AS) [1‐3] if the administrative decisions related to the network, such as the network topology, addressing scheme, assignment of addresses to the hosts, and routing decisions, can be taken by the administrator of the network. The scope of an administrative domain may not be confined to a single network but can be over a combination of networks connected to each other and sharing common routing information. Still, these networks remain under the administrative control of only one administrator for the purpose of sharing the common routing table in a centralized, shared, or distributive mode. An AS is characterized as a network in which the nodes are connected to each other in such a fashion that any node can communicate with any other node unless there is some link or node failure in the network. The routers in an AS share routing information among each other, using a common routing protocol, and the network is managed by a single organization.

Generally, two different ASs are connected across a geographical distance over a wide area network, and the Internet service provider (ISP) provides the connectivity to ...