Originally two AAL types, AAL types 3 and 4, were combined in support of both connection-oriented and connectionless traffic.Examples include X.25 packet and Frame Relay traffic.

• 最初的两种AAL类型，AAL类型3和类型4组合在一起支持面向连接和无连接传输业务，例如，X.；25信息包和帧延时传输。