Sunday, December 5, 2010

Salient features of the BGP routing protocol

* Border gateway protocol - as the name implies it is a protocol used among gateway nodes of the ASs

* Focuses on reachability (loop free) rather than optimality. - why? - it is hard to come across a single routing metric since transit ASs have different internal routing protocols and routing metrics.

* Trust is important in BGP - because it relies solely on route advertisements from peers

* Does not fall into distance vector or link state routing - advertizes complete path as a list of ASs

* Looping within BGP is avoided by advertising complete path AS prefixes - if an AS already sees itself in the list, it determines that the path is no longer useful.