ATM is a standards-based multiplexing and switching technology used to deliver multimedia services over broadband networks. It uses fixed length cells and virtual circuits to transport data, voice and video traffic in a rapid manner while providing deterministic behavior between endpoints in the network.

The key ATM features include:
• set up of end-to-end data paths using standard signaling and ATM routing
• segmentation of packets into cells and re-assembly at the destination
• statistical multiplexing and switching of cells
• network wide congestion control
• advanced traffic management functions including:

- negotiation of a ‘traffic contract’ to determine the parameters that affect the end-to-end delivery of packets
- traffic shaping to maintain the traffic contract
- traffic policing to enforce the traffic contract
- connection admission control to ensure that traffic contracts of new customers do not adversely affect existing customers

There are several advantages to using ATM for providing multimedia transport services. It uses virtual circuits to set up an end-to-end data path for which a quality of service (QoS) can be guaranteed in a deterministic fashion. Also, ATM switches interpret cell headers on the fly, using embedded information to efficiently route traffic through the switching fabric. This dynamic method of path determination provides enormous scalabilty and network adaptability. It also allows the ATM network to provide excellent traffic management capabilities. Finally, ATM is the first worldwide standard to be embraced by the computer, communications, and entertainment industries as a means of supporting multimedia traffic, including video, audio, voice and data. North American and European telcos and PTTs have been instrumental in the development of these standards over the past several years in the ITU, ANSI and ATM Forum.

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