Abstract

In the past, branch office sites rarely had efficient and cost-effective connections to corporate LANs. Leased lines offered good performance but often at too high a price, while inexpensive dial-up analog links proved too slow for handling bandwidth-hungry LAN applications. Neither of the available connectivity options could deliver both acceptable performance and reasonable cost. Today, the Integrated Services Digital Network (ISDN) presents a viable option. ISDN is an increasingly popular wide-area network service that combines high bandwidth (from 64 Kbit/s to 128 Kbit/s) with a cost-effective, usage-based dial-up implementation. The worldwide availability of ISDN brings high-powered internetworking into the realm of possibility for the remote office user.

In addition to being a viable option for a primary connection, ISDN can be employed as a secondary connection between distant LANs. When used as a secondary connection in conjunction with leased lines, ISDN provides supplemental “bandwidth-on-demand,” or emergency backup in the event of a primary service failure.

Ascom Timeplex commissioned The Tolly Group to demonstrate the effectiveness of two of their ISDN products: the SYNCHRONY AR and the SYNCHRONY ER. The Tolly Group examined several aspects of ISDN that are important to branch and headquarters use: 1.) basic dial-on-demand connectivity for primary ISDN connections, 2.) leased-line backup, and 3.) bandwidth-on-demand.