CANOGA PERKINS CanogaOS Configuration Guide - Manual (Page 136)

CanogaOS Configuration Guide
Proprietary & Confidential Canoga Perkins Metro Ethernet Switches Page 136 of 350
18 Configuring BGP
18.1 Overview
The Border Gateway Protocol (BGP) is an inter-Autonomous System routing protocol.
The primary function of a BGP speaking system is to exchange network reachability
information with other BGP systems. This network reachability information includes
information on the list of Autonomous Systems (ASes) that reachability information traverses.
This information is sufficient for constructing a graph of AS connectivity for this reachability,
from which routing loops may be pruned and, at the AS level, some policy decisions may be
enforced.
BGP-4 provides a set of mechanisms for supporting Classless Inter-Domain Routing (CIDR)
[RFC1518, RFC1519]. These mechanisms include support for advertising a set of destinations
as an IP prefix and eliminating the concept of network "class" within BGP. BGP-4 also
introduces mechanisms that allow aggregation of routes, including aggregation of AS paths.
Routing information exchanged via BGP supports only the destination-based forwarding
paradigm, which assumes that a router forwards a packet based solely on the destination address
carried in the IP header of the packet. This, in turn, reflects the set of policy decisions that can
(and cannot) be enforced using BGP. BGP can support only those policies conforming to the
destination-based forwarding paradigm.
For more BGP information, see [RFC 1771, RFC 4271].