B-ISDN and the OSI protocol reference model

The evolution of public telecommunication networks toward broadband integrated services digital networks (B-ISDNs) is presented. The asynchronous transfer mode (ATM), which supports B-ISDNs, and the B-ISDN protocol reference model are discussed. It is shown that the service offered by the ATM layer in the B-ISDN protocol reference model is equivalent to the service offered by the OSI physical layer. It is also shown that the service offered by the ATM adaptation layer (AAL) type 3/4 is similar to an OSI data link service. The emergence of the metropolitan area network (MAN) standard as an intermediate support for broadband services and the similarities between the DQDB MAC and the AAL type 3/4 in its connectionless mode are discussed.<>