Asynchronous Transfer Mode (ATM)

Asynchronous transfer mode (ATM) is a cell-oriented switching and multiplexing technology that uses fixed-length (53 byte; 48 bytes of data, and 5 bytes of header information) packets — called cells — to carry various types of traffic, such as data, voice, video, multimedia, and so on, through multiple classes of services. ATM is a 1 connection-oriented technology, in which a connection is established between the two endpoints before the actual data exchange begins. ATM provides a highly complex technology, with features intended for applications ranging from global telco networks to private local area computer networks. ATM has been a partial success as a technology, with widespread deployment, but generally only used as a transport for IP traffic; its goal of providing a single integrated end-to-end technology for LANs, public networks, and user services has largely failed. However, as it often happens in technology development, various important ATM concepts have been inherited by other technologies, such as MPLS. To accelerate the deployment of ATM technology, the ATM Forum, a consortium of service providers and equipment vendors in the communication industries was created to develop implementation and specification agreements. Later, ATM Forum was merged with other industry forums to form MPLS Frame Relay ATM (MFA) forum [23]. In this chapter, we present a brief overview on ATM protocol layers, the current status on Traffic Management, and discuss related technologies such as MPLS, as well as technologies using the ATM protocol layer stack, such as DSL, FTTP, and UMTS.