BT’s intention to retire the UK integrated services digital network (ISDN) infrastructure by 2025 heralds the start of a ten year process for migrating all ISDN and PSTN customers to Session Initiation Protocol (SIP) Trunking.

Although new to most UK businesses, SIP is more familiar in the US and much of Continental Europe where the market has moved beyond the early stages to the mainstream. In 2013, Verizon announced it would no longer take orders for ISDN service in the North-Eastern United States and in Germany today, new ISDN lines are no longer available and existing lines are to be phased out by 2018.

With most of its Central and Eastern European networks already running all-IP, Deutsche Telekom is on track to meet this deadline, says Kevin Baynes, Country Manager, Sonus UK & Ireland.

According to a 2015 Infonetics Research report into SIP Trunking Services, the market is expected to reach $8.5 billion by 2019 with 43 million SIP trunks in service. So why the world moving to SIP? The answer is that although ISDN is a robust and reliable technology, it simply doesn’t support the same functionality, flexibility and ROI when compared to SIP.

The SIP environment benefits

SIPs simplified architecture allows enterprises to reduce costs, rapidly deploy new applications and solutions and seamlessly grow as their business does. This is because voice, video and data can all be consolidated on the same service provider’s “pipe” as part of a Unified Communications (UC) model.

This means one monthly bill, one central server from which to deploy UC across your entire enterprise network and, as your business grows, one call to your SP and the bandwidth required for new connections can be added within hours. Billing and cost accounting as well as dial plans, compliance recording and more, can also be centrally managed by IT managers when SIP is combined with an SBC.

Because SIP trunking is based on the Internet, it essentially take location out of the equation. This means you can establish Points of Presence (POPs) in local areas where you do business without having a physical presence there. A local number can be dialled by a customer, even if you are based in another country, making your organisation look more local. In reality the call is routed via the ITSP to one of your locations, eliminating the need for off-putting long distance calls or 0800 numbers.

SIP Trunking is available today from a wide range of carriers, cable operators, ISPs and competitive providers around the world. Although there are hundreds of providers, the installed base has become concentrated with the large operators because in a service market based on lower cost, scale is crucial for business success.

AT&T, Level 3, Verizon, XO, CenturyLink, Sprint and Windsteam have started to dominate the market and in Europe it is the big incumbent providers such as Deutsche Telecom, Telefonica and Telstra. BT is following suit.

SIP Environments and Session Border Controllers (SBC)

Whichever region you are in, there are a couple of tried and tested recommendations when considering migrating to SIP:

Firstly – read the small print on your service level agreement carefully as this will set out in black and white what you should expect in terms of network uptime, call completion rates and quality score.

Secondly – invest in a Session Border Controller (SBC) for SIP-based communications. This is crucial for preventing cyber-crimes like communications-based denial of service (DOS) attacks. Unlike traditional firewalls, which aren’t prepared for real-time SIP traffic, SBCs for SIP environments support security features such as topology hiding, encryption and more.

Security is only part of SBC’s value; it is the glue that lets different UC systems, codecs and SIP implementations “talk” to each other. It also enables your legacy telephone network and new IP-based PBX work together so you if you do decide to migrate to SIP Trunking, you don’t have to throw out your existing phone system.

Best of both worlds

As ISDN takes a bow from the global stage, organisations that have not already migrated to SIP would do well to deploy an SBC in anticipation of the inevitable move. With an SBC in place today, you can start saving money immediately and it will make the migration to SIP much simpler when the time comes.

The author of this blog is Kevin Baynes, Country Manager, Sonus UK & Ireland

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