ISO/IEC 14476-2:20 03是ITU-T Recommendation X.ectp ISO/IEC 14476的组成部分，其主要标题为增强型通信传输协议，其是一系列旨在支持多播传输服务的协议规范。 ISO/IEC 14476-1提供了用于单工多播传输的各种协议操作的规范。这些协议操作包括连接管理，例如连接创建/终止和连接暂停/恢复，成员管理，例如延迟加入、用户离开和成员跟踪，以及用于多播数据传输的错误控制，例如错误检测和恢复。 ISO/IEC 14476-2:20 03提供了用于在单工多播传输连接中实现期望的服务质量的QoS管理规范。 ISO/IEC 14476-2:20 03描述了以下QoS管理操作: a)QoS协商对于QoS协商，本说明书假定组播应用服务的期望QoS等级可以用一组QoS参数来表示。QoS协商是通过在发送方和接收方之间交换控制分组来执行的。发送方提出从应用的要求获得的QoS参数的目标值，然后每个接收方可以基于其系统和/或网络容量提出修改的值。发送方对接收方提出的修改值进行仲裁。QoS参数的目标值可以用作预留网络资源的输入参数。b)QoS监控ECTP中的QoS控制基于来自接收器的控制分组的反馈。来自接收器的反馈消息使得发送器能够跟踪活动接收器的数量，并且还能够监视用于多播数据传输的连接状态。QoS监测被设计成允许发送方根据QoS参数值诊断连接状态，并因此采取必要的动作以将连接状态维持在期望的QoS水平。监控的连接状态将报告给发送端的应用程序。所传送的信息可以提供用于计费目的的统计数据，例如。c)QoS维护基于来自接收器的反馈信息，发送器采取一个或多个动作以便将连接状态维持在期望的QoS水平。这些QoS维护动作包括数据传输速率的调整、连接暂停和恢复、麻烦制造者弹出和连接终止操作。这些QoS监控和维护功能，基于监控的参数状态，提供速率-基于拥塞控制。 ISO/IEC 14476-2:20 03是ITU-T建议草案X.ectp ISO/IEC 14476的组成部分，该草案有6个部分。所有协议组件，包括ITU-T建议草案X.606 ISO/IEC 14476-1中规定的分组格式和协议过程，在ISO/IEC 14476-2:20 03中也是有效的。

ISO/IEC 14476-2:2003 is an integral part of ITU-T Recommendation X.ectp | ISO/IEC 14476 having the main title of Enhanced communications transport protocol, which is a family of protocol specifications designed to support multicast transport services. ISO/IEC 14476-1 provides a specification of various protocol operations for simplex multicast transport. Those protocol operations include connection management such as connection creation/termination and connection pause/resume, membership management such as late join, user leave and membership tracking, and error control for multicast data transport such as error detection and recovery. ISO/IEC 14476-2:2003 provides a specification of QoS management for accomplishing desirable quality of service in simplex multicast transport connection. ISO/IEC 14476-2:2003 describes the following QoS management operations:

• a) QoS negotiation
• For QoS negotiation, this specification assumes that a desired QoS level for multicast application service can be expressed in terms of a set of QoS parameters. QoS negotiation is performed via exchange of control packets between sender and receivers. Sender proposes the target values of QoS parameters obtained from the application's requirements, and then each receiver can propose modified values based on its system and/or network capacity. Sender arbitrates the modified values proposed by receivers. Target values for QoS parameters can be used as input parameters for reservation of network resources.
• b) QoS monitoring
• QoS control in ECTP is based on feedback of control packets from receivers. The feedback messages from receivers enable the sender to keep track of the number of active receivers and also to monitor the connection status for multicast data transport. QoS monitoring is designed to allow the sender to diagnose the connection status in terms of QoS parameter values, and thus to take the necessary actions for maintaining the connection status at a desired QoS level. The monitored connection status will be reported to the application at the sender side. The information conveyed could provide statistics useful for billing purposes, for example.
• c) QoS maintenance
• Based on feedback information from receivers, the sender takes one or more actions so as to maintain the connection status at a desired QoS level. These QoS maintenance actions include adjustment of the data transmission rate, connection pause and resume, troublemaker ejection and connection termination operations. These QoS monitoring and maintenance functions, based on monitored parameter status, provide rate-based congestion control.

ISO/IEC 14476-2:2003 is an integral part of ITU-T draft Recommendation X.ectp | ISO/IEC 14476, which has 6 parts. All the protocol components, including packet formats and protocol procedures specified in ITU-T draft Recommendation X.606 | ISO/IEC 14476-1, are also valid in ISO/IEC 14476-2:2003.