Chapter 2: ISDN Helps People Work Together

ISDN: Dialed LAN Connectivity

ISDN offers a better way. Using single BRI connections dialed through standard telephone lines, a growing array of ISDN LAN bridges and routers offer fast, virtually immediate high-speed inter-LAN connections.

When information needs to be sent to or retrieved from another LAN, an "intelligent" bridge automatically dials and establishes a 64Kbps connection through a single B channel. If higher bandwidths are needed, a second B channel is automatically dialed and bonded into the connection for transmission speeds of 128Kbps before compression.

When transmission is completed, the entire connection is automatically torn down. Users pay only for actual transmission times rather than expensive dedicated digital circuits.

The result is a virtual, on-demand connection to every LAN or host on a corporate campus - as well as most vendor and customer systems - for literally the cost of a dialed telephone call.

Are speeds fast enough? The answer is an enthusiastic yes, especially from users who have in the past tried to link LANs using analog modems or X.25 packet switching. For while the data rates of ISDN do not come close to the raw speeds of a LAN, the unshared bandwidth of ISDN has proved that it can produce almost the same response times that users expect from an office LAN. As B-channel compression speeds continue to increase, user response times should improve just as quickly.

Some typical users of LAN-to-LAN connections include:

Deutsche Telekom, Inc., the North American sales arm of Deutsche Telekom AG in Germany, Europe's largest telecommunications company. LANs in each of its six sales offices in the United States and Canada can quickly and effectively be linked through ISDN. "Any office can get quick access to another, for file sharing, e-mail, database lookup, sales reports and more," says Horst Schad, administrative support manager. "To make a connection, all we have to do is press a function key. Disconnecting takes longer: we have to press a key twice."

Manchester Equipment Corporation, a major supplier of ISDN and other telecommunications equipment and services in the New York area. The firm is itself a committed user of ISDN for a range of dialed connectivity, with ten ISDN Intellipath(TM) lines serving its two buildings in Hauppauge. The dialed connections offer several advantages, according to Ed Hodgson, manager of consulting services. First, they establish high-speed links between LANs in each building. Using Gandalf bridges on each LAN, typical data speeds of about a megabit a second are possible.

"We used to link our LANs with Switched 56 leased lines," he notes. "Today, ISDN gives us twice the speed, and more, for about half the price."

In addition, Manchester Equipment uses ISDN to back up leased frame relay data connections to two sites in Florida, and one in Needham, MA. ISDN has also become a primary channel for video connections between these locations using Intel ProShare equipment.