信息技术 增强型通信运输服务定义

[中文适用范围]： 此建议|国际标准以抽象的方式定义了传输层提供的外部可见服务： a) 服务的原始动作和事件； b) 与每个原语动作和事件相关的参数数据； c) 这些动作和事件之间的关系以及它们的有效顺序。 本建议书中定义的服务|国际标准是由增强型通信传输协议（与网络服务结合）提供的并且可由任何应用协议使用。 该服务还可以由其他协议提供，可能每个协议都支持本文定义的服务的子集。 本建议书中指定的原语 |国际标准支持连接模式服务和无连接服务。 在支持增强通信的无连接模式服务的一些情况下，在数据传输开始之前还可能需要某些操作，例如关于服务质量的协议。 对于连接模式或无连接模式服务的数据传输阶段，可能存在一系列数据排序特征。 本建议书没有任何暗示|关于包含或排除本文指定的服务原语的任何上述特征的国际标准。 [外文原描述]： This Recommendation | International Standard defines in an abstract way the externally visible service provided by the Transport Layer in terms of: a) the primitive actions and events of the service; b) the parameter data associated with each primitive action and event; c) the relationship between, and the valid sequences of, these actions and events. The service defined in this Recommendation | International Standard is that which is provided by the Enhanced Communications Transport Protocol (in conjunction with the Network Service) and which may be used by any application protocol. The service can also be provided by other protocols possibly each supporting a subset of the services defined herein. The primitives specified in this Recommendation | International Standard support a connection-mode service and a connectionless service. In some cases of connectionless-mode service supporting enhanced communications, certain operations may also be necessary prior to the commencement of data transfer, e.g. agreement on quality of service. For the data transfer phase of either connection-mode or connectionless-mode services, there may be a range of dataordering characteristics. No implication is made in this Recommendation | International Standard regarding the inclusion or exclusion of any of the above characteristics given the service primitives specified herein.