BGP Analyses

A good routing protocol must be scalable and able to handle performance issues that arise. In this section, i will discuss about scalability and performance management wrt to BGP. All the routers in an AS are not required to participate in BGP but rather, a single router at the border is capable of handling BGP information with adjacent neighbors. It doesn't mean only a single router in an AS is capable of handling BGP updates and routing.Other routers within an AS can be set to act as multiple BGP gateway routers but however, these routers have to posses consistent BGP update information and accurate knowledge of the routes in their RIB.  Since, route processing uses the routers memory, the amount of information that the router receives and processes has to be managed for efficiency thus, incremental updates are used in BGP after the initial full update that routers exchange. This is to make sure that only what needs to be updated get updated to conserve bandwidth and power. To further ease the work of routers BGP implements route aggregation or summarisation whereby a group of networks could be represented as a single entity. For example :

12.19.0.0 is the IP block of an ISP, this ISP has about 100 networks (12.19.1.0 - 12.19.100.0) instead of this router advertising all these networks, just the block 12.19.0.0 in the routing update suffices.

In other to know an estimate amount of bandwidth information that is used during the initial update of BGP, lets assume that the total number of routes in the network is N, the mean of the AS path distance is M and the total number of the A. Assuming a uniform distribution, the worst case amount of bandwidth consumed is  O(N + M * A).