Specifies procedures for the transmission of configuration and routeing information between network entities, the encoding of the protocol data units used for the transmission of the configuration and routeing information, procedures for the correct interpretation of protocol control information, and the functional requirements for implementations claiming conformance to this standard. Procedures are defined in terms of the interactions between Intermediate System Network entities through the exchange of protocol data units, between a Network entity and an underlying service provider, and the constraints on route determination.