==Phrack Inc.==
           Volume One, Issue Two, Phile 6 of 9

Toward Universal Information Services Via ISDN

by Taran King From PROTO newsletter of AT&T Bell Laboratories

Phase one, the Present.

The local network of today, although still largely voice-oriented, is already on the path to Universal Information Services. Lightguide fiber is dramatically expanding the capacity of local networks, helping to lower the costs and increase the demand for high-band width, Information Age services. And public networks are increasingly digital and geared for data and special services. For example:

Today's public networks consist of multiple or overlay networks. The public switched network, or circuit network, mainly for voice, is the base network. Two kinds of overlay networks provide special services. Channel networks carry private lines leased by large customers and transmit much of today's data and image traffic; they also handle traffic for network operations support. Packet networks carry data communications, while packet switching is used internally to public networks for common channel signaling to set up, route and take down calls, or to give customers information.

"Overlay networks help telecommunications companies efficiently meet growing demand for digital transmission and special services," says Stan Johnston, Market Planning Manager, Network Systems Evolution, in AT&T Network Systems. "Their integration into a single network, however, would be still more effective."

Phase two, the Integrated Services Digital Network (ISDN).

The ISDN is a concept to which AT&T is committed - and it's the foundation for Universal Information Services. The central idea of ISDN, as AT&T Network Systems sees it, is to provide an individual user a link to the local central office of generous band-width - a digital subscriber line that can carry 144,000 bits per second (sure beats 2400 baud!). The band-width is subdivided into two 64,000-bit channels, which may carry voice or data or both, and one 16,000-bit channel for packetized signaling information or data transport. Such a link provides convenient "integrated" network access by accommodating voice, data and signaling over a single line.

The ISDN will make it easier for a customer to get varied services from public and private networks. More bandwidth for big customers will be available through another ISDN access standard, the extended digital subscriber line, which provides 1.5 billion bits per second as 24 channels of 64,000 bits each.

In 1986, new software from Bell Labs will enable the 5ESS switch to accommodate ISDN-sized 144,000-bit channels that standardize and simplify subscribers' use of local networks. AT&T is committed to future products that will also be ISDN-compatible. Other vendors, too, some of whom already plan to build premises, terminal, and other equipment to ISDN standards, will make ISDN a cooperative effort.

By providing integrated digital access to networks, ISDN will make important progress toward the goal of Universal Information Services. But overlay networks will continue to divvy up the transport job. And messages needing less than 144,000 bits per second will not fill their allotted bandwidth, leaving capacity underutilized.

Phase three, Universal Information Services.

Rooted in the fertile ground of 5ESS switches, ISDN equipment and technologies such as wideband packet transport, Universal Information Services will bear fruit during the 1990s. From a single kind of network will hang services as different as apples, oranges and pears. Just as network access was integrated in ISDN, transport functions will increasingly be integrated by powerful new network equipment evolved from equipment developed for the ISDN. Where customers once got standard-sized ISDN channels, they'll get big bandwidth for large jobs, little bandwitdh for small jobs.