This Recommendation/International Standard specifies a protocol that is used to provide the connectionless-mode Network service described in CCITT Rec. X.213 / ISO/IEC 8348 and to perform certain Network layer management functions. The protocol relies upon the provision of an underlying connectionless-mode service by real subnetworks and/or data links. The underlying connectionless-mode service assumed by the protocol may be obtained either directly, from a connectionless-mode real subnetwork, or indirectly, through the operation of an appropriate Subnetwork Dependent Convergence Function (SNDCF) or Protocol (SNDCP) over a connection-mode real subnetwork, as described in ISO/IEC 8648. This Recommendation/International Standard specifies the operation of the protocol with respect to a uniform, abstract underlying subnetwork service. Other Recommendations/International Standards specify the way in which this underlying subnetwork service is obtained from real subn etworks, such as those which conform to ISO/IEC 8802 or ISO/IEC 8208. The underlying subnetwork service may be obtained from real subnetworks other than those that are specifically covered by the other Recommendations/International Standards.
This Recommendation/International Standard specifies
(a) procedures for the connectionless transmission of data and control information from one Network entity to a peer Network entity;
(b) the encoding of the protocol data units (PDUs) used for the transmission of data and control information, comprising a varia ble-length protocol header format;
(c) procedures for the correct interpretation of protocol control information; and
(d) the functional requirements for implementations claiming conformance to this Recommendation/International Standard.
The procedures are defined in terms of
(a) the interactions among peer Network entities through the exchange of protocol data units;
(b) the interactions between a Network entity and a Network service user through the exchange of Network service primitives; and
(c) the interactions between a Network entity and an abstract underlying service provider through the exchange of service primitives.
This Recommendation/International Standard also provides the PICS proforma for this protocol, in compliance with the relevant requirements, and in accordance with the relevant guidance, given in CCITT Rec. X.290 / ISO/IEC 9646-1.