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SIP takes over the need for ISDN …

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The Integrated Services Digital Network (ISDN) has been with us for almost 25 years and has transformed to a large extent the entire telecoms industry. It would also be true to say that the adoption of digital services within the UK’s enterprise community via the use of ‘ISDN’ PBXs became the de-facto connectivity standard many years ago.

What is interesting to note however is that despite the term ‘Integrated’, ISDN was and still is, primarily a telephony service; a digital switched voice network providing better quality calls than the previous analogue environment and at what was (before the introduction of SIP), ultimately a more competitive price. Yet with ISDN30 just a convenient way to provision exchange lines (and ISDN2 to a lesser degree),  we’ve had to wait until the realisation of high availability IP networks and principally the widespread acceptance of SIP before terms like  ‘unified communications’ could have any real meaning.

The total number of ISDN channels in the UK peaked in 2007 at approximately 4.7 Million and has been in major decline ever since, losing by the end 2012 almost a quarter of its all-time high.

This move away from ISDN has been defined by a number of factors, including the now ubiquitous use of mobile phones as well as the more significant migration to all things SIP. It’s also worth noting that whilst the current industry forecasts for SIP (SIP trunking in particular) represent in effect a direct alternative to ISDN, the actual number of channels replaced is often fewer, simply because customer audits reveal what for many what was an historic over capacity; net result, for every 10 ISDN channels lost, only 8 might re-appear as SIP; not a great incentive for the ISDN based incumbents thinking of replacing their installed base.

So, having accepted that the overall decline in ISDN as inevitable, the only real debate is how fast?  How quickly will we reach the tipping point and what happens when we do?

Arguably all IT/Comms managers responsible for their companies communications needs will be under no illusions about the future of voice; endorsed by their own PBX suppliers who have no doubt been extolling the virtues of IP and UC for many years. For many customers therefore, and particularly for those with existing WANs, the only legacy architecture that remains is the ISDN connection to the PSTN itself.

So the question remains; whilst most have some migration strategy in mind, (and for many that reality might be that their ISDN PBX just isn’t IP compatible), what would happen if the decline in ISDN become a stampede?

Not as far-fetched as it might first appear, consider what might happen if some European Telco announced the end of life for their own ISDN service? It has to happen at some point and there’s no reason to think it wouldn’t be sometime within the next few years. How would the market react? What would the other Telco’s do? How many would follow suit?

More importantly, how might that impact customers whose only real strategy was to wait and see; anticipating a move to SIP only once they’d extracted the very last drop of use from their legacy PBX?

It would be reasonable to expect that such a situation would see a wholesale rush to exit ISDN; with a  snow-balling  effect fuelled as vendors and service providers attempt to cater for what would undoubtedly represent a major period of disruption and by equal measure, opportunity.

Such a rapid change to the telecom landscape would also focus thoughts on supply and demand, making for an interesting debate on the current competitive nature of SIP.

Consider also the markets ability to meet the demand. Upgrading software levels on PBXs in order to cater for SIP, replacing entire systems or at the very least, sourcing, installing and configuring ISDN/SIP gateways.

From the SIP provider’s perspective, the volume of installations would dictate the need to have at the very least a high volume industrialised approach to provision, how many existing providers could lay claim to having that? A few, not many. There would certainly be winners and losers.

The real point of this exercise is to anticipate and consider the options, the industry accepts the inevitable decline of ISDN and as we’ve clearly seen it’s well under way. The notion that something may happen that would dramatically increase the rate of this decline is not unrealistic and if we’ve learned anything from human nature it is to expect the unexpected.

So from a customer’s perspective, whatever their strategy, the longer they delay the move to SIP, the greater their chances of having to do it in a hurry – and that’s not good for anyone.