本标准是关于宽带综合业务数字网（B-ISDN）的一系列美国国家标准之一。这些标准描述了B-ISDN能力、架构模型和网络接口，包括协议功能和规范，以及信令特性。本标准描述了恒定比特率服务（CBR AAL）的ATM适配层协议。ATM适配层（AAL）执行必要的功能，使ATM层提供的服务与AAL服务用户所需的服务相匹配。 它向用户提供ATM层无法提供的服务。本文档主要介绍恒定比特率服务的ATM适配层。以前称为T1。630-1999（R2005）。

This standard is one of a series of American National Standards on Broadband Integrated Services Digital Network (B-ISDN). These standards describe the B-ISDN capabilities, architectural model, and network interfaces including protocol functionalities and specifications, and signaling characteristics. This standard describes the protocol of the ATM Adaptation Layer for Constant Bit Rate Services (CBR AAL). The ATM Adaptation Layer (AAL) performs the necessary functions to match the services provided by the ATM Layer to the services required by the AAL service user. It provides to its users services that are not available from the ATM Layer. This document concentrates on the ATM Adaptation Layer for Constant Bit Rate Services. Formerly known as T1.630-1999(R2005).