本建议|国际标准规定了一种协议，用于提供ITU-T Rec.X.213 | ISO/IEC 8348中描述的无连接模式网络服务，并执行某些网络层管理功能。该协议依赖于通过真实子网和/或数据链路提供底层无连接模式服务。协议假定的底层无连接模式服务可以直接从无连接模式真实子网获得，或者通过连接上的适当子网相关收敛函数（SNDCF）或协议（SNDCP）的操作间接获得- 模式实子网，如ISO/IEC 8648所述。本建议|国际标准规定了协议在统一、抽象的“底层子网服务”方面的操作。其他建议|国际标准规定了从实际子网（如符合ISO/IEC 8802或ISO/IEC 8208的子网）获取“基础子网服务”的方式。“基础子网服务”可从实际子网获得，而非其他建议|国际标准中具体涵盖的子网。本建议|国际标准规定: a） 将数据和控制信息从一个网络实体无连接传输到一个或多个对等网络实体的过程；b） 用于传输数据和控制信息的协议数据单元（PDU）的编码，包括可变长度协议报头格式；c） 正确解释协议控制信息的程序；d）声称符合本建议|国际标准的实施的功能要求。这些程序定义为:a）对等网络实体之间通过协议数据单元交换的交互； b） 网络实体和网络服务用户之间通过交换网络服务原语进行的交互；c）网络实体和抽象底层服务提供者之间通过交换服务原语进行的交互。本建议|国际标准还根据相关要求和ITU-T Rec.X.290 | ISO/IEC 9646-1中给出的相关指南，提供了本协议的PICS形式

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