“Just what are ‘SIP Trunks’, and why do I need to know about them?”

Our old, but trusted Public Switched Telephone Network (PSTN), with its analogue lines, ISDN2 and ISDN30 lines, is to disappear in the UK by 2025. Telephony is moving from PSTN to more modern and flexible SIP Trunks.

The world’s big telecom providers are phasing out their old PSTN fast, and are moving customers to Voice over Internet Protocol (VoIP). So – a phone system upgrade and an introduction to VoIP in the near future is going to be inevitable.

Phone companies like BT will begin ISDN switch-off by 2020. In the UK, ISDN lines are down to less than 3 million, from 4.7 million in 2007 – and the trend is accelerating. In 2017 major telco’s such as BT, KPN, France Télécom, Deutsche Telekom and Telecom Italia began to phase out ISDN lines.

As a result, ‘Session Initiation Protocol’ (SIP) trunking increased by 62% in 2015 from the prior year, driven primarily by North American adoption. A SIP Trunking service is usually provided by an internet service provider (ISP). Unlike a PTSN carrier, the lines carrying your calls are not physical lines, but ‘virtual line channels’ within your Broadband / DSL Internet connection. The service provider rents you a number of ‘channels’ depending on the maximum number of calls you want to make & take at any one time. They also issue phone numbers and lines, usually at better rates than the traditional providers and with more flexibility and shorter contract periods.

This guide explains what SIP Trunks are, their advantages and how you can make the move.

What are SIP Trunks?

They are VoIP phone-line channels delivered through an Internet connection using SIP to set-up and control the call, and real-time data packets to carry digitally coded voice. World-wide adoption of this ‘standard’ protocol to connect & control the progress of a telephone call, means that connection between different brands of phone system and different phone-sets running SIP, is possible. Telecom service providers rent out groups of channels to be ‘assigned’ to your telephone system and out-going calls made on those channels are billed to your account. In a modern IP-PBX, this channel assignment is usually done by software configuration, without needing to add hardware to the system and through a single data cable connecting your phone system to your computer network. Direct Dial Inwards (DDI) phone numbers are linked to your SIP trunk so that calls can be guided directly to individuals or business groups by your phone system. In many cases existing numbers used on analogue and/or ISDN lines, can be ported into the SIP Trunk service so you don’t have to carry out a campaign to tell your customers your new numbers! Charged ISDN supplementary services such as blocks of DDI numbers and Caller ID, are included with a SIP Trunk service as standard, and usually at no additional rental cost.

On-premises phone system solutions act as the end-point for the SIP Trunk service which delivers calls to your software PBX (e.g. 3CX) or Appliance (e.g. Yeastar S-Series). This solution allows you to add and remove services from multiple carriers to get favourable tariffs for all call types and destinations without trade-offs. On-premise solutions allow you to be in control of SIP Trunk allocation, and get the most favourable call tariffs to your advantage.

Hosted VoIP solutions terminate SIP Trunk services on the hosting company’s own Internet-based ‘Cloud’ Server, with fewer call-routing and feature choices. Tariffs are usually based on call-minute packages provided by a single carrier or reseller. The SIP Trunk services are controlled by the Hosted VoIP provider in the case of Cloud telephony – to the advantage of the hosting provider.

Benefits of SIP Trunking

Our farewell to the PSTN brings many benefits. SIP Trunks will deliver:

  • Lower monthly Line & DDI rentals – The install charge & monthly rental to have a number of ‘lines’ installed at your office drops significantly. DDI numbers either cost a lot less – or are free!
  • Lower call charges – There are many SIP Trunk providers and competition combined with a simplified transmission network, has driven down call charges significantly. Local call rates have been cut dramatically, and you can save on international calls too.
  • Better customer service – Provide better customer service by adding more geographical and international numbers. Add numbers to your SIP Trunk and terminate them on your IP-PBX quickly and easily. You can give customers more options to dial in at a significantly lower cost, even long distance. Its easier for your customers to contact you and you’ll provide a better experience for customers doing business with you.
  • Move offices and keep the same number – SIP Trunks are not bound to a location, so it’s easy to move offices without having to change your stationary or inform your customers. There is no longer a need to pay to forward phone calls to the new offices.
  • Eliminate VoIP Gateways – SIP Trunks will eliminate the need to buy and manage VoIP Gateway hardware (e.g. changing VoIP to ISDN for your old telephone system). All phone calls come in via Internet and are handled by software. No translation or conversion often means better call quality too.
  • A Production tool – Modern IP PBX / Unified Communications solutions will give customers increased productivity, mobility and boost sales. Connecting an IP-PBX to SIP Trunks is much easier than via the PSTN. You can go on-premise or hosted, the choice is yours.
  • Flexibility – It’s quick & easy to add channels to your SIP Trunk account to cope with increased calls. A simple phone call will allow you to add (or reduce) channels, and often this can be done in minutes – with little or no installation fees. Compare that to the cost and delay in having additional ISDN lines installed – and then having to hardware-upgrade your old PBX to handle more lines!
  • Correct number of channels – With SIP Trunks, you can easily choose the correct number of channels that you need. Using ISDN/E1, you often have to choose to add either 15 or 30 lines. This usually means you end up with expensive extra capacity.

Selecting the right SIP Trunk provider

The next step is to choose a Provider who will supply your SIP Trunks & DDI numbers. A few factors come into play when making this decision:

  • Security – As SIP Trunks are exposed to the Internet, it is very important that the Provider has a well secured network and an anti-fraud system in place. Your network firewall must be configurable to block unwanted SIP ‘phishing’ – and the anti-fraud system must monitor the system and provide protection when call quantities and destinations are ‘unusual’.
  • Own network – Does the SIP Trunk provider run their own network or is it a rebranded service? There are quite a few tier-two providers reselling SIP Trunks from other Providers. Select a provider who has control over their service and network.
  • Competitive Cost – Costs vary widely between services. Some vendors will overcharge for SIP Trunks. Look for competitive rates – but – ensure that you are getting business quality SIP Trunk services. For example, telecom providers will provide a cheaper quality to Internet call shops. Be cost-conscious, but expect to pay a bit more for business class service.
  • Number Porting – Can the provider port your phone numbers? Ensure that you choose a provider who can port all the existing numbers – not all providers are able to do this for all regions.

Upgrading Internet connectivity

Once you have selected your SIP Trunk provider, consider a dedicated Internet line for the SIP Trunk, or a high capacity fibre-based broadband or leased line if voice and data are shared. Most firewalls can handle multiple WAN connections, and, considering the low cost of an Internet line in most places, a separate VoIP connection will be the most reliable way to ensure the quality of your VoIP calls.

Some SIP Trunk providers bundle their service with a dedicated Internet line, router and network switch. This keeps your voice traffic separate from your data traffic – but can have a downside regarding integration of voice & data. Much will depend on the cost and your existing network infrastructure. Check that your firewall is up-to-date and will be capable of handling VoIP traffic correctly.

Upgrading the PBX to an IP PBX

Chances are that your trusted old PSTN lines are connected into another old device, the hardware-based Private Branch Exchange (PBX) system. This device is inflexible, difficult to manage and often expensive to maintain. Technically it is possible to buy a gateway that allows the old PBX to talk to the SIP Trunks. But why not upgrade to a modern IP PBX and leverage the flexibility and modern features IP telephony can bring to your business phone system. This allows you to take advantage of the cost savings, easy management, and productivity increases with full-scale Unified Communications that an IP PBX offers. You can choose from a hosted PBX, an appliance PBX, or a software-based PBX.

It’s new and exciting times for telecommunications – with a lot more choice than you may think! Contact us at Foxhall Solutions to talk about how your next telephone system will help your business …