Let's get this straight: there is certainly a place for convergence. In the right circumstances, with the right topography and with the right business drivers, Voice Over IP (VOIP) makes sense… in the same way that in the right situation wireless LANs make sense… or outsourcing… or any one of a dozen other 'must have' technologies.

I am getting a little bit tired of being cold-called by salesmen wanting to arrange meetings and to take a 'few details'. "What are your plans for convergence?" they ask or "What is your wireless strategy?" I remember them asking much the same sort of question about ASPs a couple of years ago. On being told that we have no plans, or that our strategy is not to go anywhere near the technology in question, their tone of voice implies that we are poor unenlightened souls who live in the dark ages.

But we're far from the dark ages here. We have an extensive data network based on a 622Mbit/s core with switched Ethernet edge devices and dedicated outlets in every master and boy's room and in many other locations. We also have a conventional telephone system based on a PABX housed in the oldest part of the school, with telephones fed by copper pairs in most of our buildings. And Eton College is a fairly large organisation, occupying more than 400 buildings that make up a large part of the town. The staff live in flats and houses spread widely around the town. There are 25 boys' boarding houses, schoolrooms, libraries, sports facilities, the administration - all the usual facilities.

The PABX is full. It does not provide us with all of the facilities we need, particularly in the areas of tracing and blocking nuisance calls. A project was initiated to find a suitable replacement system. If the prospect of such a procurement already has VoIP suppliers salivating in anticipation then the bad news is that we have already placed a contract – for a conventional telephony solution.

We shortlisted three suppliers, Telewest with their Centrex offering, and NEC and Bistech both with VoIP. Costs were broken down over a five year period, including the installation costs and the anticipated running costs based on current traffic levels. All three bids offered us savings over a five year period of around £120,000. The point is, of course, that topography and the nature of the legacy system really determine the extent of any savings. Though our buildings are spread around the town we do only have the one 'site'. There are no opportunities for savings on 'internal' traffic.

The VoIP offerings would have required extensive re-cabling as the topography of the existing telephone network is quite different to that of the data network. This expense was, however, countered by Telewest's view that most of our existing copper cabling needed replacing anyway.

With costs roughly equal, the decision rested on technical and operational criteria. A case can always be made for new technology on the basis that it is 'future-proofed', although this is not a good strategy when selling a system to a man running an ATM network. It is also possible to point to the wealth of additional features which, if not already available, are just around the corner - honest! We are but simple users in terms of telephony and whereas some of these features look nice on paper, it is pretty hard to justify them when set against the drawback.

And there are plenty of operational drawbacks. I told the VoIP resellers that I was not confident that our data network could provide a reliable enough service for our telephone users. One of the suppliers offered to build an entirely separate network alongside our existing network, just to carry the telephony. They didn’t seem to quite grasp the nature of the problem.

Our central 622Mbit/s ring feeds switches in many other locations around the school - between 50 and 60 of them. Some of these are in inhospitable environments or cramped spaces. They do not all have uninterruptible power supplies. Naturally, we manage this network to the best of our ability and put a great deal of effort into making it as reliable as possible. We protect the backbone, server rooms and other vital functions with as much power regulation as we can afford but it makes no economic sense to do so for all of our edge devices.

Most of our network issues are related to power problems. Take the case of a boarding house, home to 50 boys and related staff. A power failure in the middle of the night can leave the house without network access for some hours. We don’t have 24 hour cover for our data network. Even so, the phones in the boarding house must continue to operate – an absolute requirement for safety.

With a conventional exchange, in a central location, we can get a duty operator to investigate any problems. With Centrex we don’t even have to do this ourselves. We simply cannot get access to most boarding house switches in the middle of the night and this in itself rules out the VoIP approach.

Conventional telephone systems are hugely reliable. Data networks are still less so. In a diverse data network it surely makes little sense loading additional services onto a large number of potentially vulnerable switches unless there is some real financial or operational gain. The criteria will always differ from case to case, whatever your vendor may wish you to believe. In our case the risks were just not worth taking.

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