SIP trunking

Illustration of SIP trunking

Choosing SIP trunking for your business can give a quick and substantial return on investment.

To find out more about the benefits of IP Voice download this free report based on the feedback of 1,000 UK decision makers. Click here to view and download the report.

SIP trunking explained

A SIP trunk is a direct connection between your business and an Internet telephony service provider. If your business invests in SIP trunks, this will enable you to extend voice over IP (VoIP) telephony past your company's firewall without needing an IP-PSTN gateway.

Diagram showing how SIP trunks work

If this sounds complicated, all you really need to know is that this is a simpler configuration which is both easier and less expensive to design, operate, maintain, and upgrade. Since Internet telephony service providers deliver services (especially long distance) at substantial savings, choosing SIP trunking for your business can give a quick and substantial return on investment.  And since there is an option to retain legacy telecoms equipment when setting up your SIP solution, that investment is affordable even for the smallest business.

SIP trunking:

  • Saves you money.
  • Ensures your business continuity.
  • Provides flexibility.
  • Supports multiple locations.
  • Is easy to scale up.
  • Converges your voice and data.

SIP or Hosted Voice? Watch the video:

Download SIP Trunks BrochureSIP trunking offers your business a flexible and scaleable solution for inbound and outbound voice access to a PBX. It allows convergence of voice and data across a QoS enabled network, which eliminates the need for ISDN access and the associated costs. It also improves security and resilience, and reduces repair times. The simplicity of a converged network means less interfaces, reduced hardware costs, increased reliability and improved efficiency. Simply, the business advantages of using SIP are endless, from improvements in productivity to network cost savings, from streamlining your business processes to providing new services to your customers.  It's no wonder SIP trunking is such a hot topic right now.

Deploying SIP trunking can be a big step towards simplifying your organisation’s telecommunications and towards preparing for the latest real-time communications enhancements, but the biggest motivation for most organisations is immediate and substantial cost savings.

~ Microsoft Resource Kit Team

To find out more about the benefits of IP Voice download this free report based on the feedback of 1,000 UK decision makers. Click here to view and download the report.

SIP trunk benefits:

Save money

IP connectivity costs significantly less than ISDN, resulting in lower call charges and no charges for calls made between offices or extensions and offices, together with lower line rental costs if you have more than one site. Should you need to divert your calls in the event of a disaster, there are no expensive call-forwarding charges to pay either.

SIP trunks save money diagram

Flexibility with numbers

With SIP trunks, you can move office and keep your old geographic number, without having to pay ongoing call-forwarding charges. You won't have to order new company stationery either.

SIP trunks flexibility diagram

Business continuity

SIP trunks allow you to plan for the unplanned, enabling you to quickly and cheaply redirect your calls should your office have to move location in an emergency (see below).

SIP trunks business continuity diagram


No matter what life throws at your business, SIP trunking gives you the tools to cope. For example, when you're short staffed or managing a busy period, SIP trunks allow you to load balance your calls between sites.

SIP trunks resilience diagram

Line rationalisation

If your business has more than one site, SIP trunks provides the opportunity for line rationalisation and reduces the number of PBXs that you have to maintain, while still retaining complete control of your company's business numbers (see below).

SIP trunks line rationalisation diagram

Compatible with Skype for Business (previously Microsoft Lync)

SIP trunks can fully interoperate with Skype for Business, enabling you to make external calls by directly connecting to the Skype platform.

SIP trunks integrate with Microsoft Lync Diagram

Business continuity example set-up:

SIP trunks business continuity diagram

Line rationalisation for multiple sites:

For businesses with multiple sites and a connection into each individual PBX at each site, SIP trunks will help you reduce the number of ISDN connections needed and the associated cost. Employing SIP trunks will in addition reduce the maintenance costs on all of your various PBXs. For each remote site, the cost is simply the IP connection and required handsets. You can then pull all the telephony traffic back into your centralised PBX.

Before rationalisation:

SIP trunks diagram before rationalisation

After rationalisation:

SIP trunks diagram after rationalisation

More example SIP trunking uses:

Person using smartphoneSIP has many applications but some common reasons for businesses looking to acquire SIP trunks are:

  • Local numbers: You want to use local numbers, giving your business a local presence without having to open local offices.  As well as attracting 'local' customers, having a local number is also a positive ranking factor for your website in that area.
  • Cost savings: You use a traditional ISDN set-up at one or more of your business locations, and are looking to make efficiencies on this set-up.  SIP trunking can complement your existing ISDN lines or replace them altogether, delivering the flexibility and cost savings of VoIP.
  • Emergency/COB support: You're looking at continuation of business options and would like a resilient solution to cope with emergencies at one or more sites.
  • Moving office: You are moving office, and would like to retain your existing numbers without incurring call forwarding charges.
  • Fast set-up: As a new or expanding business, you need telephony services, and you need them set up and running fast! SIP trunks can usually be enabled in around 10 days, unlike traditional ISDN lines.
  • Feature-rich: You're looking for all the features of an enterprise grade telephone solution, but you don't really want the price tag.
  • Multisite/homeworkers: Your business has more than one site or uses homeworkers/remote workers.  You'd like free calls between SIP connected sites, and you want to be able to connect new sites and users easily and cheaply in the future.
  • Efficiencies: SIP trunking reduces the maintenance requirements of your infrastructure, while maximising available bandwidth and so allowing voice, data and video to be carried efficiently across the network using a single connection.

Call management solutions:

SIP trunking allows your business to benefit from a wide range of call management solutions, further increasing productivity and efficiency.  For example:

  • Auto Attendant: The auto attendant feature routes incoming calls through to the right person in the right department.
  • Call Centre: This feature ensures your contacts are routed through to the correct destination.
  • Call Recording: This invaluable feature is legislation-compliant, and allows you to monitor calls for training, quality control and security reasons.
  • Missed Call SMS: This feature provides an SMS text notification whenever you miss a call.
  • Fax to Email: As you might expect, this feature allows your faxes to be delivered to your email address as pdf files.
  • Follow Me: This feature allows calls to be diverted between multiple destinations, so you never miss a call wherever you are.
  • One to Fax: This feature allows your calls to be routed to a destination to receive a fax.
  • One to Many: This feature allows calls to be routed to multiple destinations enabling, for example, a number of remote workers to monitor an incoming number.
  • One to One: This feature allows a call to be routed to a single destination.
  • Outgoing Record: This provides on-demand outbound call recording which, as for inbound call recording, can be utilised for training, security and quality monitoring.
  • Ratio Divert Plan: This feature allows calls to be diverted according to the ratio set between multiple destinations.  This allows, for example, a number of operatives to call share effectively.
  • Time of Day: This allows you to set your call destinations depending on the time and/or day.
  • Voice to Email: This popular service enables you to send voice messages to your email, allowing you to collect them wherever you are at your convenience.

Hosting choices

When you implement SIP Trunks, you can choose to have your PBX located either at your business premises or housed within a managed colocation centre where power, space and support will be taken care of by experienced engineers. Both options are possible and for the ultimate flexibility and business continuity solution, a combination of both is also an option.

Dedicated hybrid hosted PBX implementation of SIP trunks

To find out more about the benefits of IP Voice download this free report based on the feedback of 1,000 UK decision makers. Click here to view and download the report.

Why choose NT for your SIP trunks?

NT's customer base spans small, medium and large businesses, solicitors, hospitals, doctors, call centres, home workers, accountants, customer care departments, call centres and many more. Established in 1986, we have helped thousands of businesses simplify their communications structure and save money over the last 30 years.

We pride ourselves in providing that friendly local service that is missing in so many large organisations today, while keeping our prices highly competitive.

Contact NT today on 01623 687750 or email to find out how a SIP trunking solution will help simplify your communications and lower your costs.