This Recommendation | International Standard specifies a protocol that is used to provide the connectionless-mode Network service described in ITU-T 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 subnetworks, 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 one or more peer Network entities;
b) the encoding of the Protocol Data Units (PDUs) used for the transmission of data and control information, comprising a variable-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 ITU-T Rec. X.290 | ISO/IEC 9646-1.