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Color images in seconds and video telephones: hot enough for you?

Color images transmitted in eight seconds and video telephones for desk to desk videoconferencing: These could be the hot devices that will stoke the fire under ISDN deployment.

A group of Wall Streeters were duly impressed by both of the applications, which owe their existence to ISDN. The folks in New York were on the receiving end of a demonstration from Chantilly, Va.

Chantilly is home to the Contel Technology Center, which reprised a demo it did last fall for a group of academic users. Contel technical staffers designed, developed, and integrated the color image transmission system.

Thanks to incredible compression and ISDN's 64 kb/s, color images can be transmitted in less than eight seconds. Contrast that with the three minutes it takes for transmission of black and white images on fax machines with gray scales, or image processing options.

The videophone setup was another crowd-pleaser, especially since the image transmission can be done at 128 KB/s, using both B channels of an ISDN line. There is some blurring of motion, but overall picture quality is high.

"This will definitely encourage ISDN," says Kap Kim, principal scientist at the technology center. "What has been needed is some sexy device to give some idea of what ISDN can do for you.

"You can talk about 2B1Q and Q.931 and most people don't care. But when they see a videophone, and realize what they can do with it, they get the message."

When enough business people demand desktop conferencing, and enough grandparents demand videophone capabilities so they can see the grandkids across the country as they talk to them, then ISDN will roll out. That's the way Kim sees it.

There were a couple of interesting sidelights to the Wall Street demonstration. First, because no ISDN link was available from Chantilly to New York (sound familiar?) the demo used two AT&T Accunet switched 56 circuits, for a total of 112 kb/s.

Also, Kim says he never gave a thought to the switches involved at the central offices. In an earlier demo with another site, there were AT&T 5ESS switches at both ends. This time, there was a Northern Telecom DMS-100 in New York. No special arrangements were made, and still the two had no trouble communicating.

The rational view

They made an interesting point about ISDN during a local area network bridging seminar at the NetWorld show in Boston.

First, the extremist views--you've heard them--were presented. One is that "ISDN shall serve the place of all networking strategies, eliminating the need for incompatible LANs, routers, fiber, and the like. Users will find eternal bliss sending data through the phones on their desks."

The opposing view is that "ISDN provides few significant capabilities beyond those achievable with a dial-up modem. ISDN has little place in the construction of real peer-to-peer data networks."

But as with so many things, the truth lies somewhere in the middle. The "rational view," as it was called, is that ISDN and existing networks should be viewed as a major application of ISDN."

Among the panelists was Dory Leifer, network manager at the University of Michigan, who talked about running IP (Internet Protocol) over ISDN. Benefits of that approach are to extend access to remote locations not served by LANs connected to the Internet; replacement of leased facilities when favorable tariffs apply or leased facilities are not available; and on-demand bandwidth to back up or supplement leased facilities.

However, Leifer concluded, IP over ISDN must be standardized, to allow "real product" development.

Working on ATM

A number of big vendors are working together on development of ATM (Asynchronous Transfer Mode) node and link systems, which will constitute the main part of a Nippon Telegraph and Telephone broadband ISDN network.

Broadband ISDN will be the core of NTT's effort to provide various new public telecommunications services, including video. The services will be provided via the two ATM systems, in accord with ATM standards in the works at CCITT.

Partners with NTT are Northern Telecom, Fujutsu, Hitachi, NEC, Oki Electric Industry, Toshiba, AT&T International, Mitsubishi, and Siemens AG.

ATM will be a key standard for broadband ISDN, providing a way to handle multimedia communications in a single system. Users will be able to pick the transmission speed they want, change the speed during transmission, or combine several different typs of communications, such as voice, image, PC, and mainframe.

ATM, for instance, will make it possible to transmit full-color, full-motion high definition TV signals over NTT's planned network.

The ATM node system's role in broadband ISDN is analogous to conventional switches in other system. The link system is analogous to conventional transmission systems.
COPYRIGHT 1991 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991 Gale, Cengage Learning. All rights reserved.

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Title Annotation:ISDN Forum
Author:Tanzillo, Kevin
Publication:Communications News
Article Type:column
Date:Apr 1, 1991
Words:778
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