Broadband ISDN and ATM
Broadband ISDN and ATM, Even if the above services become popular. the telephone companies are still faced with a far more fundamental problem: multiple networks. POTS (Plain Old Telephone Service) and Telex use the old Circuit-switched network. Each of the new data services such as SMDS and frame relay uses its own packet-switching network. DQDB is different from these, and the internal telephone company call management network (SSN /) is yet another network. Maintaining all these separate networks is a major headache, and here is another network, cable television, that the telephone companies do not control and would like to.
The perceived solution is to invent a single new network for the future that will replace the entire telephone system and all the specialized networks with a Single integrated network for all kinds of information transfer. This new network will have a huge data rate compared to all existing networks and services and will make it possible to offer a large variety of new services. This IS not a small project, and it is certainly not going to happen overnight, but it is now under way.
The new wide area service is called B-ISDN (Broadband Integrated Services Digital Network). It will offer video on demand. live television from many sources. full motion multimedia electronic mai. CD-quality music, LAN inter-connection. high-speed data transport for science and industry and many other serVices that have not yet even been thought of, all over the telephone line.
The underlying technology that makes B-ISDN possible is called ATM
(Asynchronous Transfer Mode) because it is not synchronous (tied to a master
clock), as most long distance telephone lines are. Note that the acronym ATM
here has nothing to do with the Automated Teller Machines many bankS provide
(although an ATM machine can use an ATM network to talk to its bank).
A great deal of work has already been done on ATM and on the B-ISDN system that uses it, although there is more ahead. For more information on this subject, see (Fischer et al., 1994; Gasman, 1994; Goralski, 1995; Kim et al., 1994;
Kyas, 1995; McDysan and Spohn, 1995: and Stallings, 1995a).
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