Alas poor PSTN, I knew him well
The PSTN was given the last rites many years ago and yet, it’s still around. I’ve lost count of the number of times I’ve been asked when we will see the last of SS7. What were standard predictions – 5 or 7, even 10 years now – have all come and gone, and still it persists.
While some were preparing to shout, “The King is dead; long live the King!” he foiled them all and went into remission. Since then, it’s been a case of ‘the King is in his counting house, counting out his money’ and the VoIP Prince has had to be content with a war of attrition.
While it’s fair to say that for the last ten years or so, there have been no new infrastructure investments in the circuit switched network, the sheer size of it has meant that its outright replacement is something that couldn’t be readily contemplated. And that’s why it’s become a war of attrition.
Slowly, but surely, it’s melting away, but when there are approximately 1.4 billion active landline subscriptions globally (note 1), the infrastructure needed to service that many end points remains a significant entity. You’d be right to say the dog has had its day, but the truth is, there’s life there yet.
Beyond the obvious signs of life – a good part of that 1.4 billion still uses fixed line phones – the major area of activity within the circuit switched technology market involves media gateways. In fact, that’s even more the case as that consumer figure doesn’t account for the billions of TDM end points installed within corporate enterprises and SMBs around the world. So it’s true to say that if there is going to be a significant investment in equipment with a legacy network element, it’s likely to include a gateway.
The primary reason for that is the need for interworking between new, next generation networks and the substantial rump of the persistent fixed line network. Never the twain shall meet is not to be contemplated. On the contrary, every service provider wants – and needs – to be able to offer its services to the largest possible subscriber/consumer base. In some cases, that’s a legislative need, such as in NG9-1-1 or 112 environments, whilst in others, it’s purely economical.
There are many market sectors in which gateways are needed. Apart from the obvious need for citizens to be able to reach an IP-based PSAP when dialling 112 from their landline phone in an emergency, there are many public and private organisations with interconnectivity requirements.
If you label the basic requirement as SS7-to-SIP interworking, there are many examples, from large customer care centres, through a variety of service delivery platforms to lawful intercept, where such capability needs to be deployed.
At an enterprise level, there are many needs for gateways. Some requirements are related to specific protocols in a particular territory as is the case with DPNSS in the United Kingdom. Other requirements involve interconnecting IP PBXs to the PSTN or connecting a legacy ISDN PBX to a SIP trunk.
Such needs are commonplace and many unified communications vendors have an ongoing need for gateways as they seek to migrate their customer base from legacy equipment to modern, software-based solutions. The same applies when responding to opportunities and RFPs in competitive situations.
You might think that all of those needs would have been satisfied long since, however, that is patently not the case. The inertia of the installed base of business users of legacy equipment is only now beginning to be overcome. In addition, as IP networks evolve and transform, correspondingly new gateway functionality will be needed to maintain interconnectivity.
Reports of the demise of the King are premature. The harbingers of doom will have to be patient. Someday, we will see their predictions come true, but until then, “All hail the Gateway!
1.International telecommunication union, managing the information society report 2012