TABLE OF CONTENTS Stewart Day
Hewlett-Packard Australia Ltd., Victoria, Australia
Asynchronous transfer mode (ATM) is the base switching technology that the ITU-T (formerly CCITT) chose for the Broadband Integrated Services Digital Network (B-ISDN). Though it was originally envisioned that ATM be deployed once the new broadband services appeared, industry (particularly through the ATM Forum) has accelerated the practical application of the technology to the point where ATM itself is becoming the enabler for new services. In addition, ATM is being used to solve existing problems such as LAN interconnection and the continued evolution of MANs and WANs (metropolitan area and wide area networks). ATM can be deployed in all types of local and wide area networks.
ATM is a cell-based architecture. Cells are short, fixed length-packets. ATM cells, each with a fixed length of 53 bytes, can be processed more efficiently than bit streams or variable-length packets. This efficiency allows high-bandwidth switching and multiplexing in both local and wide area environments.
Cell technology provides a powerful mechanism for transporting different traffic types on a common communications infrastructure. By keeping cells small and regular, real-time traffic (such as voice and video) can be segmented and packetized, then multiplexed onto pathways carrying other traffic types (such as data) without loss of quality.
A second advantage of ATM is the ability to maximize switching efficiency and bandwidth usage. In existing Time Division Multiplexed (TDM) networks, data is divided into...
