BGP Crash Course


BGP: A "path vector" protocol used for inter-AS communication (RFC 1771).

BGP is a policy-oriented protocol.  Consists of:
Protocol: How ASes talk to each other.
Import/Export Policies: Language that indirectly affects best route choices and readvertisements.
Decision Process: Process by which a "best route" is selected.

How does it work?
Route advertisements: neighbor announces reachability to a certain prefix (e.g., 12.0.48.0/20)
Any network that hears this advertisement can (presumably) send traffic destined for that prefix to that neighbor.