Purpose of a routing protocol and autonomous systems

Purpose of a routing protocol and autonomous systems 

6.2.3 
This page will explain why routing protocols and autonomous systems are used.
The goal of a routing protocol is to build and maintain a routing table. This table contains the learned networks and associated ports for those networks. Routers use routing protocols to manage information received from other routers and its interfaces, as well as manually configured routes.
The routing protocol learns all available routes, places the best routes into the routing table, and removes routes when they are no longer valid. The router uses the information in the routing table to forward routed protocol packets.
The routing algorithm is fundamental to dynamic routing. Whenever the topology of a network changes because of growth, reconfiguration, or failure, the network knowledgebase must also change. The network knowledgebase needs to reflect an accurate view of the new topology.
When all routers in an internetwork operate with the same knowledge, the internetwork is said to have converged. Fast convergence is desirable because it reduces the period of time in which routers would continue to make incorrect routing decisions.
Autonomous systems divide the global internetwork into smaller and more manageable networks. Each AS has its own set of rules and policies and an AS number that will distinguish it from all other autonomous systems.
The next page will introduce the two main classes of routing algorithms.