next up previous
Next: Gigabit Networks Up: Other Networks Previous: ISDN

ATM Networks- Broadband ISDN

A more recent approach to the increasing demands for bandwidth is ATM. ATM stands for ``Asynchronous Transfer Mode'' and gives bandwidths from 25 Mbit/s. One application the telephone companies have in mind for ATM is ``video-on-demand'', i.e. you sit at home and instead of sending away the spouse to the local video shop you can call a database provider who will then direct a data stream containing the video and audio information of the chosen film directly to you.

Alternative approaches to the ``video-on-demand'' problem involve combinations of standard telephony (for a data control channel) and cable-TV for the distribution of the film. Basically you can receive a particular film at a free channel in the cable network after you have ordered it via the telephone. Another technique currently used for this is ADSL. A fast digital connection (1Mb) is used to send the video/audio information in a compressed form to the home.

There is some concern that there will not be enough demand for the kind of bandwidth provided by ATM, but this seems to be a question of price policies and cost of access equipment.

For music related interactive real-time applications it seems particularly important that ATM is claimed to provide guaranteed bandwidth and delay times (although this point is under discussion). The Internet (or ATM) as it is today is not sufficient since it cannot guarantee a fixed bandwidth and maximum delay times as needed for highly demanding applications. It is likely that the Internet will gradually provide better performance and there are ongoing discussions on how to change the protocols to meet this demand.



Thomas Sjöland
Thu Mar 16 12:05:17 MET 1995