Connection Management for an ATM Network

Asynchronous Transfer Mode (ATM) is a switching and transmission technique in which all information is carried in short fixed-length packets called cells. By interleaving information from many sources at the cell level, services with widely-varying requirements can be carried, including fixed and variable bit-rate streams, real-time and non-delay sensitive traffic and services with widely differing bandwidth requirements. ATM networks can accommodate applications ranging from multimedia conferencing with voice, video and graphical content, through standard voice grade telephony to file transfer and messaging. ATM has been adopted by the CCITT as the target transfer mode for the Broadband Integrated Services Digital Network (B-ISDN). This has given impetus to the process of standardization of protocols based on ATM. Apart from the physical layer, however, only two layers have so far received much attention; these are the ATM layer that deals with the cell headers, and the ATM adaptation layer (AAL) that deals with such issues as segmentation and reassembly and rate adaption. In order to mount some of the novel and complex applications envisioned for ATM networks, services must be provided at layers above the adaptation layer. These higher layers are for further study and there is an urgent need for them so that the capabilities of ATM networks can be fully demonstrated. This article addresses one of the areas in which further work is required. We examine in detail the facilities required to control and manage multiservice applications. The proposed techniques are embodied in connection management procedures. These procedures form the basis of the services in the control pane in the B-ISDN protocol stack. These types of services are often referred to as ''signaling mechanisms''. Here, connection management encompasses such mechanisms, but our scope is wider than this. To allow maximum flexibility, an application may use several unidirectional point-to-point or point-to-multipoint channels, that are logically associated in a call. An application may have two or more participant users and each user may need multiple outgoing or incoming channels. The connection management services described in this article provide the procedures needed to ensure that the channels and users are brought together into a unified framework. The services required are structured into a layered model, including layers for group, call, channel and circuit management. This paper describes the ATM network environment, examines service requirements for multimedia applications, and discusses architectural models. These sections set the context for the main body of work reported herein. The next sections cover related work in the research community ad in the emerging standards forums, proposed connection management facilities for multiservice networks in detail, and a number of example applications showing how the management procedures can be applied. The final section summarizes the advances made and indicates opportunities for further work.