A collection of IP networks and routers under the control of one administrative entity.
- Identified by a unique AS Number (ASN), assigned by IANA.
- Contains multiple routers and uplinks to other ASes.
- The boundary between AS domains defines the boundary between Intra-AS and Inter-AS routing.
Routing
Intra-AS
Operates within a single AS. Aka. Interior Gateway Protocol (IGP).
Inter-AS
Operates between different ASes. Aka. Exterior Gateway Protocol (EGP).
| Scope | Principle | Protocols |
|---|---|---|
| Intra-AS | Distance Vector | RIP |
| Intra-AS | Link State | OSPF, IS-IS |
| Inter-AS | Path Vector | BGP |
See Routing for algorithm details.