This International Standard specifies a protocol which is used by Network Layer entities operating the protocol specified in ISO 8473 in Intermediate Systems to maintain routeing information for the purpose of routeing within a single routeing domain. The protocol specified in this International Standard relies upon the provision of a connectionless-mode underlying service.

This International Standard specifies: a) procedures for the transmission of configuration and routeing information between network entities residing in Intermediate Systems within a single routeing domain; b) the encoding of the protocol data units used for the transmission of the configuration and routeing information; c) procedures for the correct interpretation of protocol control information; and d) the functional requirements for implementations claiming conformance to this International Standard.

The procedures are defined in terms of a) the interactions between Intermediate system Network entities through the exchange of protocol data units; b) the interactions between a Network entity and an underlying service provider through the exchange of subnetwork service primitives; and c) the constraints on route determination which must be observed by each Intermediate system when each has a routeing information base which is consistent with the others.