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Monday 30th of November 2009

SS7 – Reports of its death are somewhat premature

by Robin Kent
February 27, 2009

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At the start of the 21st century, many people in the telecommunications industry were predicting the death of SS7 as a mass market signalling protocol.

It was seen to be too old, too expensive and not advanced enough to cope with the changes that were predicted to revolutionise telecoms such as convergence; a move to all IP; and increased video consumption over the Internet.

However, SS7 hasn’t laid down and died. While many predicted its demise, SS7 now underpins the delivery of many so-called ‘next generation’ fixed and mobile services.

As network technology advanced at the start of the 21st century, SS7 was, we were led to believe, all set to be replaced by more advanced signalling protocols that could support more complex Value Added Services (VAS).

At this time, many telecommunications manufacturers were switching their attention from SS7 to what they considered to be its replacement, IP.

Telecommunication operators were busy planning network upgrades while service providers were dreaming up next generation IP-driven services that would guarantee new revenue streams and reduce costs.

Many believed that all of this would mean root and branch changes to their existing signalling infrastructure. Even industry analysts Forrester Research predicted that by 2010, 45 per cent of the voice telephone market would be handled by VoIP technologies.[1]

It seemed that the end was in sight for SS7 and that with new IP networks would come new signal processing protocols and codecs.

However, what was predicted by some industry luminaries couldn’t have been any further from the truth.

Rather than being phased out and consigned to the long list of redundant networking technologies, the use of SS7 has actually grown since the start of this decade.

In a 2006 report, industry analysts Venture Development Corporation said that the “2005 market for SS7 Network Elements was approximately $7 billion and is predicted to grow to almost $8 billion by 2008.[2]

This is backed up by a recent survey conducted by Adax Europe[3], 72 per cent of telecommunication vendors had not phased out SS7 entirely.

The question is why?

SS7 was developed in the 1980s to overhaul the world’s existing telecommunications infrastructure. By creating a common signalling protocol, it was thought it would make interoperability between the different national telecommunications networks easier, rather than being developed in the piecemeal fashion that they had been since the start of the 20th century. SS7 was designed with the aim of being a universal signalling protocol.

It was designed to be robust, stable and, most importantly, able to cope with the anticipated increase in demand for channels placed on the telecommunication industry that would result from more people using more advanced telecommunications services.

In this respect, SS7 has fulfilled its role perfectly. It is this stability and reliability that has given it longevity.

SS7 offers a much greater level of reliability than IP at the moment; it was designed to provide the most stable network possible. IP, by its nature and design, does not offer the same high levels of reliability.

Whilst SIGTRAN attempts to address this problem at protocol level, it is still dependent on the inherently unstable IP transport.

As a result of this, many operators who have looked to transfer to an IP infrastructure have instead just moved their media traffic to IP and left the signalling to SS7 to ensure network stability and performance.

Nevertheless, it hasn’t just been SS7’s inherent reliability that has helped it maintain its position. As mobile phones have become more and more popular, users have been taking advantage of the value-added services (VAS) they offer, such as SMS and MMS.

These services are supported by SS7, and the SMS revolution would not have happened were it not for SS7.

As the popularity of text messages has increased, so too has reliance on SS7 as operators have looked to manage these value-added services.

The same can be said for services on fixed-line networks, such as caller ID, call waiting and tele-voting.

Whilst most VAS applications are supported by the IP signalling protocol SIGTRAN, there has not been a wholesale switch.

This has mainly been because most VAS applications are SMS-based, and so work best when supported by SS7, especially with the development of more secure SMS based services such as pre-pay and bill payment.

Telecommunications operators have so completely adopted SS7 it is now an entrenched part of their networks and it is still being used because the inherent benefits of the protocol far outweigh those of converting SS7 to IP.

It would also require considerable investment.

The SS7 installed base is so huge that if an operator is looking to expand his network or increase subscriber capacity, it is probably more cost effective to expand their existing SS7 network than to build a whole new IP-based infrastructure.

The number one priority of telecommunication operators was, and always must be, to ensure the consistency and quality of service (QoS) of their networks.

Migrating from a well established technology to its successor is always going to result in teething troubles, but the longer this can be put off the better, especially in the current economic environment where operators are putting major CAPEX projects on hold.

In a 2007 research note from Venture Development Corporation, they say that “…major threats [from VoIP towards SS7] are not expected for another 5-10 years when more and more IP-to-IP calls begin to penetrate”.[4] This is reinforced by the 72 per cent of people surveyed by Adax who hadn’t yet phased out their SS7 infrastructure or plan to in the near future.[5]

So, while many predicted the demise of SS7, it has had a lifespan that most technologies can only dream of, and which doesn’t seem to be coming to an end of anytime soon.

As for the next five years, there is likely to be an expanding subscriber base in emerging markets like India, China, Brazil and Africa which will drive continued, growth in SS7.

After this time we may then see a gradual tailing off in growth, but we won’t see the sudden fall in SS7 usage that was predicted five, or even three, years ago and which was heralded to be the death knell for SS7.

It seems that there is life in the old horse yet.

Robin Kent is the director of operations at Adax Europe.


1 “European Incumbent Telcos VoIP Road Map.” Forrester Research, Inc., Lars Godell. October 2003

2“A White Paper on: 2005-2006 Telecom Core Infrastructure Market Intelligence Service” Venture Development Corporation, Robert Johnson. August 2006

3 “Is SS7 Still Alive and Kicking?” survey, Adax Europe, 1 May 2008

4 “A Research Note On: Signalling Networks are Dead. Long Live SS7!” Venture Development Corporation, Laurie Seymour, July 2007.

5 “Is SS7 Still Alive and Kicking?” survey, Adax Europe, 1 May 2008

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