MICROTEL/11/1

ISDN multiplexer boosts communications efficiency in award-winning recruitment company

ISDN multiplexers supplied by Microtel are being used in a novel way to boost efficiency and create cost savings for an award-winning computer recruitment company.

Computer Futures, a market leader in the IT staffing sector, is using the PRI-MUX devices (manufactured by DATAX, a Telindus company) to interface between its internal routers and PABX systems and external BT and other carriers' ISDN networks, in such a way that the system is automatically configured to provide the most cost-effective use of resources.

The fast-growing recruitment company operates a number of offices in the UK and mainland Europe, all of which are critically dependent on telephone systems for their operation. Essentially, each office is a call centre with recruitment consultants sitting at terminals and talking to employers, contractors and candidates while simultaneously accessing information from their comprehensive database.

The core voice communication link to each office is an ISDN 30 connection, typically delivered on the BT fibre network, which also provides the WAN link to the database servers. A second ISDN 30 link over copper cable - BT's CWSS (Copper Wideband Serving Section) HDSL system - is used for data communication. The critical nature of these links in providing both voice and data communications means that back-up is essential to eliminate any chance of down-time, and this was initially provided by the company installing a second ISDN system to take over if the main fibre link failed.

It soon became apparent, however, that this was an expensive solution, requiring a full back-up ISDN system that was not being used most of the time. As a result, Rob Robb, IT Infrastructure Manager at Computer Futures, suggested that redundancy could be provided by developing a system that could reallocate the voice and data channels between the two existing links so that either could provide full back-up if the other went down. An important requirement was that it should be a system with central management that could be standardised over the whole of the company's operations in whatever location and country.

Initially, Computer Futures Group IT Department contacted Microtel (part of the Kenton Research Group), with whom they had dealt before on the development of customised interfacing solutions, to see if they could produce such a system. It turned out that this was unnecessary, since they already had a standard product – the DATAX PRI-MUX - which could be used in this application.

The PRI-MUX is a four-port device which essentially acts as a configurable smart ISDN multiplexer. It was originally developed to provide least-cost routing and switching between ISDN networks, a facility not currently being used by Computer Futures but by no means ruled out if the costs of the different carriers change substantially in the future.

The unit consists of a 4-port ISDN switch with a time-division multiplexed (TDM) cross-connect capability. An on-board SNMP (Simple Network Management Protocol) agent facilitates system management, and the LAN port also features Telnet and TFTP protocols. Full self-diagnostic capabilities are also included.

In the Computer Futures installation, the four ports are linked to the main BT ISDN fibre system, the BT copper data connection, the in-house Lucent Index PABX system and a CISCO router. With all four ports enabled, the multiplexer provides total flexibility in allowing the ISDN channels to be cross-connected between lines and equipment. In addition to providing a facility for automatically reallocating channels in the event of any problems, the unit is fully programmable by the user, and provides full visibility, reporting and alarm capabilities on everything that is happening in the system. All live traffic is continuously monitored, and each unit can be remotely re-programmed to stop, re-route and answer calls. There is total flexibility of access between ports, and total control over the back-up scenario in the event of any faults.

It also offers an easy route to expansion when an office outgrows the basic 30 channels, since additional channels can be added on the back-up circuit rather than adding a complete new 30-channel system. The company is also looking at the possibility of using the capacity it offers for video-conferencing services.

Computer Futures will eventually have 24 sites throughout the UK and mainland Europe fitted with the PRI-MUX system. Each site is provided with a very advanced level of software support thanks to the SNMP software facility, which gives the company's managers to ability to reconfigure any of the remote sites as system requirements change. All configuration details are downloaded over the WAN using TFTP and kept at a central location with tape back-up, so that they can be instantly downloaded to provide back-up in the event of a problem.

The Telindus PRI-MUX also gives good status and call trace facilities, so that the unit itself can be used to check whether the configuration is correct and that calls are being routed correctly.