Autonomous Systems (contd)
One router represents the AS to the external world (the core and other AS). This router also collects reachability info (“external routes”) from other AS and diffuses it into its domain.
AS is identified by a 16-bit AS number
Traffic types: Local = traffic originating or terminating at AS. Transit = non-local traffic
AS types:
- Stub AS => only single connection to one other AS => it carries only local traffic.
- Multihomed AS: Connected to multiple AS, but does not allow transit traffic
- Transit AS: carries transit traffic under policy restrictions