vISDN networking

The Problem

Many organisations make use of ISDN2 connections for data communication between branch offices. For example, ISDN2 can be used to support email or to share documents between users in different locations.

The most common arrangement is to use ISDN2 bridges or routers to link local area networks in two offices. When a user in Office A carries out an action which requires access to Office B, e.g. copying a file from the remote office, a dial-up connection is made automatically over ISDN2 for the duration of the transaction.

ISDN2 bridges have been available for many years and are widely used by many organisations working out of multiple offices. However, there are several significant drawbacks with this form of communication:

• Call charges are incurred for the duration of each access. Even very short calls (a few seconds) may incur a minimum call cost.
• Costs cannot be budgeted. Generally, running costs are only known when quarterly bills are received.
• ISDN2 bridges can be difficult to configure and are notoriously temperamental. Many users report spurious opening of the ISDN2 line resulting in call charges even when the connection is not intentionally being used.

The result is that many users report ISDN2 telephone bills running into several thousand pounds per annum.

In addition, when using the remote access, it takes a certain time to establish the connection which can make the facility appear relatively unresponsive.

The Solution

As part of the IT infrastructure provided by Cygnet Solutions to support the distributed workforce, Cygnet has developed the ‘vISDN’ solution. This allows existing ISDN2 lines between offices to be utilised in a different way. Instead of using ISDN2 bridges, Cygnet installs special firewall/routers at each site which connect to existing ISDN2 lines. The offices are then connected by a Virtual Private Network (VPN) via the Internet.

The Cygnet vISDN solution provides a number of benefits:

• The total fixed cost of running the link (64K single channel) is approximately £820/annum per site—this includes line rental costs – there are no additional call charges. For 128K dual channel use, the total cost is £1350/annum.
• The link is ‘always on’ and can be used 24 hours per day, seven days per week, without incurring any additional charges
• The connection between offices is permanently open – there are no dial-up delays
• A version of vISDN is available to support voice calls in addition to data traffic over a single ISDN channel—all without call charges

Any organisation using ISDN2 lines for inter-office communications should consider use of Cygnet’s vISDN solution. The pay-back time can be less than 3 months!

For further details please contact brian.higton@cygnets.co.uk. C