routing domain (RD)

A routing domain is a subnet in which a group of topologically contiguous end systems use the same Layer 3 protocol and support a routing instance.

Routers within the same domain communicate using interdomain routing protocols known as Interior Routing Protocol( IRP), such as Intermediate System to Intermediate System Protocol( IS-IS) or Open Shortest Path First( OSPF). Routers in different domains operate with an Exterior Routing Protocol( ERP) such as the Interdomain Routing Protocol( IDRP). Routing domains are uniquely identified by their Routing Domain ID( RDID).