12 March 2014
A SIP (Session Initiation Protocol) trunk is a connection between an organisation and an internet telephony service provider (ITSP).
What is SIP trunking?
A SIP trunk essentially removes the need for a direct
connection to a public switched telephone network (PSTN) and
enables the customer to facilitate VoIP calls in a much faster,
simpler and less-expensive fashion. SIP trunking can therefore
provide a quick and substantial return on initial investment
and is becoming the unified communications method of choice for
As well as allowing VoIP calls, SIP trunks are also capable of
delivering instant messages, multimedia conferences, data and
other SIP-based, real-time communications services. As trunks
become more all-encompassing, additional layers can be added to
allow for more communication services to be delivered.
What are the main drivers for SIP trunking
The major driver of SIP trunking adoption is said to be its
cost efficiency. Having a SIP trunk removes the need to have
both a primary-rate interface (PRI) and a VoIP connection,
meaning that businesses and organisations only need to pay for
a connection to a SIP-enabled unit to connect to the wider
On top of this, it is much easier to add extra capacity to the
SIP connection than it is with a PRI, which has limited
bandwidth. Should a company wish to expand its capacity without
a SIP trunk, the company would likely have to purchase another
PRI connection to fulfil its needs. With a SIP trunk, a company
would only need to expand its bandwidth on the same link,
incurring a much lower cost.
Industry experts at Forrester Research estimate that companies
that adopt SIP trunking over traditional TDM systems could save
up to 35% in revenue following the changeover.
Disaster recovery is said to be another USP for SIP trunking,
which allows a call to be redirected in the instance that a
connection is lost. Additional buildings and phone lines can be
added to the SIP trunk with ease and temporary locations can be
connected and disconnected quickly and efficiently thanks to
its ability to reroute.
Which carriers are pioneering SIP
In December last year, Colt extended its SIP trunking offering
– Colt VoIP Access – to focus on the
disaster-recovery aspect of the service.
The European operator implemented advanced security functions
to allow customers in the region to more easily secure their
The upgraded service is designed to protect against attacks
such as eavesdropping and interception, and offers online
analysis of traffic, performance and network utilisation, as
well the ability to generate call-monitoring reports.
Customers are said to be looking for more secure unified
communications and Marta Muñoz Méndez-Villamil,
research director, telecommunications at IDC EMEA, believes SIP
trunking holds the answer.
"Increasingly, customers who are seeking an enhanced voice
provider require guarantees that their business-critical and
back-office functions can be ably supported by their SIP
trunking or VoIP service provider," Méndez-Villamil
says. "Colt’s solutions and their cross-Europe
capabilities mean that multi-branch offices can expect the same
service, no matter where they operate."
Earlier last year, US operator Sprint recognised the growing
demand for SIP trunking and rolled out its solution in 12 European
countries, including Austria, Belgium, Denmark, France,
Germany, Ireland, Italy, Netherlands, Spain, Sweden,
Switzerland and the UK.
Tim Donahue – VP of solutions and international sales
at Sprint – highlighted flexibility and scalability as
the key advantages of SIP trunking and believes it is a
technology which is only set to grow over the coming
"We are pleased to extend these benefits to businesses with
operations in Europe," he says.
What is the future for SIP trunking?
A study from telecoms company XO Communications estimated that
by 2016, 92.7% of phone lines will be SIP-based.
Industry expert Michael Cavanaugh believes that SIP will open
up a much wider pool of unified communications services. Video
calls and conferences via SIP trunking are starting to be
implemented around the globe and this service is only set to
become more streamlined and more efficient.
With much SIP trunking activity occurring in Europe, US cable
provider Comcast is looking to give the service more of a
presence in the US in 2014.
At a conference in New York in December last year, John
Guillaume, VP of product management and strategy at Comcast
said that its SIP trunking trials had been running very
It plans to roll out the service nationwide by the end of 2014,
which will not only focus on SMEs but also larger
"SIP is the natural next stepping stone to complete
[Comcast’s] portfolio; 85% of the market is still
PRI, but SIP is at 15% and growing fast, instead of being a
declining market," Guillaume says.