The death of ISDN?


With far more reliable and powerful broadband, EFM and GEA available, we examine the increasing use of SIP Trunks as a viable alternative to traditional lines and reveal the additional features and benefits they can provide.

A latest SIP survey in January this year showed that the SIP/IP trunking market shows no sign of slowing down with growth of 25% June-December 2014. The market has seen a growth of 60% year on year since 2012.

Exploring what were the key customer drivers, although costs versus ISDN is still the most important, there is an increasing understanding that other benefits such as ‘Flexibility’ and ‘Business Continuity’ are also key.

In the coming year we expect to see more focus on what applications can be layered on top of a SIP trunk, and how Services Providers can really address Hybrid Hosted and SIP environments and bring benefits of Unified Communications to both traditional PBX and hybrid customer scenarios.

Because all the services are in the cloud you get extension dialling across sites by default and the ability to intelligently link any mix of traditional PABX, Hosted UC sites, home and mobile workers across the business estate.This presents a compelling and powerful business case for the customer that extends beyond simply reducing their access charges.

Another recent innovation is our introduction of burstable SIP Trunks. This means that a multi-site customer can oversubscribe the trunks at a site level to allow them to “borrow” spare capacity from other sites if their local traffic demands it. This ability to rationalise total trunks, and have them dynamically available at whichever site they are needed, is naturally a persuasive proposition for the customer.

Key Question:

Are users sufficiently confident in SIP to ditch their ISDN lines?

Stephen Ashley-Brian, Product Manager – SIP Trunking at Gamma, says that the figures speak for themselves; with over 1 million ISDN channels having ‘disappeared’ since 2008, SIP has been a major benefactor. The question of confidence is therefore largely redundant as pretty well all the elements needed to ensure call quality are well understood by both vendors and customers alike

Jon Nowell, Head of Communication Services Product Management at TalkTalk Business: Not completely – telephony still remains the number one mission critical service and not all SIP services provide the SLAs and SLGs that businesses need. Resellers need to guarantee and deliver the same level of reliability that users have come to expect from ISDN, while providing easy migration and interoperability with existing PBX systems.

But for that confidence to be well placed, organisations should ensure that they follow a few simple rules:

  • Ensure that you purchase SIP trunking from a trusted provider, with a resilient infrastructure and watertight SLA. If possible, try to go with a personal recommendation from another business that has already made the switch.
  • Ensure that your broadband is up to the job. SIP trunking is only part of the equation – If your ISP is unreliable, your broadband connection is not optimised for VoIP (too much latency or jitter), or you use the same connection for voice and data, you are likely to run into problems.
  • Always have a backup. With the cost of SIP trunking and business broadband reducing all the time, you can afford to have a backup SIP trunking solution and broadband connection from a different vendor, and still save money compared to ISDN.

SIP is a main line product and has been for the past few years. Companies will only change from ISDN to SIP when there is a compelling driver or trigger such as, moving, changing telephony application, upgrading replacing a data circuit, disaster recovery applications etc.

Very small businesses are likely to only have a broadband running on an analogue line. Typically they are ok with the idea that if the broadband line goes down for some reason then they can shift their communications to a mobile device.

We are seeing more and more uptake in SIP from customers that were traditionally ISDN customers. In the past, a lot of providers were offering services without the proper infrastructure, and that obviously affected reliability. SIP’s reputation has improved enormously, and that is due to the improved quality of services offered.

Also, whilst some established businesses are more hesitant to move from an existing ISDN set up to SIP, this hesitation simply doesn’t exist in businesses seeking brand new VoIP solutions – regardless of their size. With a blank canvas, many decision makers are choosing to ditch contracts and restrictions in favour of the lower cost and faster setup of SIP – although of course it’s important to ensure the internet connection will support their required capacity.”

Are there real cost savings to be made?

Ashley-Brian at Gamma: If the ROI model with SIP trunks gave the wrong answer, there would be virtually no VoIP in the market at all. As this is clearly not the case, the commercial model already makes sense for large sections of the market. The key though is to consider all the elements that factor into cost. It’s easy to try to draw comparison in terms of lines and minutes and in many cases, particularly with the introduction of competitive access options such as EFM and FTTC that’s all you need. Just as important though are the factors that help drive operational costs down; ones that can be directly attributable to SIP. Think of the operational management tasks such as flexing channels, new service deployments, adding DR capabilities etc.

In any cost saving exercise there are a number of factors to take into account, primarily your starting position. There are two main reasons why end users opt for SIP and the two reasons can and do overlap. The flexibility SIP offers companies large and small over ISDN has saved thousands of pounds as companies are not restricted to a locally hardwired based exchange. With SIP the exchange moves into the cloud. Wherever a data circuit is connected calls can be made and received, voice is an additional application delivered over a data connection so no need to pay for an ISDN circuit and a data circuit. The saving whether in pounds, shillings and pence or via flexibility are real.

Business continuity remains paramount for users considering a change in their voice or data infrastructure. By phasing the introduction of SIP into a business network, resellers give users time to adapt and familiarise themselves before the full roll-out is complete. Disaster recovery is on one the big selling points for SIP trunks as against less flexible ISDN connections. SIP trunk services allow each DDI number to have its own individual ‘unreachable’ destination set such that if a call cannot be delivered to the PBX for any reason, all inbound calls will be diverted to the alternative number automatically (for example to the DDI owner’s mobile phone). Customers really love the idea of being in total control of their inbound traffic during these times of stress.


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