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SIP Trunking For Small And Medium-Sized Businesses

SIP Trunking

Phone systems are the lifeblood of many businesses, and owners and managers will often invest heavily to ensure that they have the most functional equipment possible. Unfortunately, as with so many modern technologies, maintaining the tools that you require to complete your work can be difficult - especially with industries like telecommunications, where equipment evolves so quickly.

If you need to replace or update your old system to ensure that it still works as well as possible, then SIP trunking is likely to be an excellent choice for you. To find out more about what it offers, simply continue reading this page. If you want to start comparing quotes today however, you only need to complete the form above.

Comparing SIP trunking quotes with Approved Index is free, quick and easy, and it could save you a considerable sum.

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What is SIP Trunking?

If you’re planning to upgrade or expand your legacy telephone system, take a close look at SIP trunking. It’s a digital communications circuit that could save you money, reduce the complexity of your infrastructure and help you take full advantage of the advanced features and services of Voice over IP (VoIP) or Unified Communications (UC).

  • SIP, which stands for Session Initiation Protocol, is an internationally recognised protocol for signalling and controlling multimedia communication sessions.
  • SIP trunking is a telecommunications circuit that uses Internet Protocol (IP) technology to replace legacy PSTN (Public Switched Telephone Network) or ISDN cabling and offers a wide range of financial, business and operational benefits.
  • A study by research firm Infonetics found that installations of SIP trunking grew by 50 percent between 2013 and 2014. The firm commented, “Business VoIP services have moved well beyond early stages to mainstream, strengthened by the growing adoption of SIP trunking and cloud services worldwide.”

SIP Trunking Benefits

The sections below outline a number of advantages that your business can benefit from. These advantages range from operational to financial, and the information provided can be a helpful way for businesses to understand the impact that SIP trunking could have.

Although these benefits may not always be entirely clear-cut, they can give excellent insight into why SIP trunking is valued by so many business users.

Reduce Local And Long-Distance Call Costs

SIP trunking connects your PBX (Private Branch Exchange) or IP-PBX to an Internet Telephony Service Provider (ITSP) to give your business access to VoIP features and services. Your users make and receive calls in the normal way.

Service providers offer different pricing packages to suit individual calling patterns. SIP services reduce your call costs by allowing you to make local, long-distance or international calls as if you were dialling a local number.

If you make a lot of international calls, choose a service provider that specialises in calls to your main destinations. That way, you can take advantage of competitive rates, reducing your call costs further.

Simplify Infrastructure

SIP trunking transmits voice calls on a data network, which means it can also carry data, video and Internet traffic. This eliminates the cost and effort of installing, managing and supporting separate circuits for voice and data. You will also reduce administration costs by dealing with a single supplier for your infrastructure services.

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Connect Different Sites

By using SIP trunking, businesses with a number of different sites can eliminate duplicate PBXs and other infrastructure equipment. SIP trunking provides a single, centralised solution that can deliver the same services and features to all sites. This simplifies communications management, saves space and reduces your infrastructure and energy costs.

Share Capacity

As an added bonus, SIP trunking can simplify your capacity requirements. With legacy systems, you would need to install additional fixed circuits to cover increases in call volumes.

SIP offers two flexible options to deal with variations in traffic for businesses operating on multiple sites. Your service provider can increase capacity on demand or, for short-term requirements, you can take advantage of a SIP feature called Pooled Concurrent Call Paths. This means that any spare capacity in your network can be used to handle higher than average call traffic at any of your sites.

Ensure Call Quality And Reliability

SIP Trunking 2

Digital circuits like SIP trunking provide higher levels of reliability than the legacy PSTN networks they replace, maintaining service levels and reducing maintenance requirements. Reputable SIP service providers incorporate Quality of Service and failover options in their networks to keep your callers connected.

Some SIP providers will also extend their circuits to cover the “last mile” which is generally supplied by the legacy PSTN network provider. This option helps businesses where call quality is critical benefit from an end-to-end SIP circuit.

However, performance is dependent on your network performance. MPLS or un-contended IP Connections provide the right performance levels, but connections over broadband may affect SIP quality.

Maintain Security

Service providers offer different levels of security. To protect networks, privacy and data, security measures should incorporate Session Border Controllers, secure VoIP interconnects and separate network access routers to stop denial of service attacks.

You must also ensure your firewall is configured correctly to allow the calls in, but keep security threats out.

Improve Business Performance

SIP trunking helps deliver the full business benefits of VoIP. When VoIP travels over conventional Local or Wide Area Networks (LANs or WANs), it can deliver a wide range of voice–based services and features, including Presence, call forwarding, voicemail and Unified Messaging.

SIP trunking takes VoIP further. It also carries video, data and Internet traffic, giving you the opportunity to take advantage of other VoIP services like video and web conferencing, multimedia screen sharing and web applications. Services like that deliver all the productivity, collaboration and flexibility benefits of VoIP to your employees.

As an added business benefit, your service provider can give you telephone numbers from anywhere in the country and route the calls to your SIP service. This helps you provide a local service for customers without having to set up a physical office.

SIP Trunking Financial Benefits

  • Calls between company sites are free.
  • Long-distance calls travel via a local number, reducing charges.
  • Reduces infrastructure and associated space, power and support costs.
  • Dealing with a single provider reduces administration costs.

SIP Trunking Operational Benefits

  • Reliable, secure, high-quality network
  • Evolutionary migration path to an all-IP environment
  • Eliminates duplication of infrastructure and support tasks
  • Eliminates fixed legacy circuits
  • Shares idle capacity across the enterprise

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Choosing a SIP Trunking Specialist

While SIP trunking enhances VoIP systems, you can also use it to adapt existing telephone system to operate over the Internet instead of the PSTN. That means you can keep legacy equipment and link it to an Internet telephone service provider. That way you get the benefits of VoIP and can then migrate in stages to a full VoIP solution.

SIP trunking is available from a number of service providers. Here we've compiled a brief review of some of the leading UK providers:

Gamma Telecom Logo

Gamma Telecom

Gamma SIP Trunks connect your business with the company’s nationwide network. It gives you access to the PSTN and provides a more flexible and lower cost alternative to ISDN for inbound and outbound voice calls. Gamma’s service can support connections ranging from two channels for small PBX-equipped businesses to an unlimited number of channels for large enterprises and contact centres.

Redcentric Logo


Redcentric’s SIP trunking service provides IP based connectivity for existing IP PBXs. The service provides full PSTN equivalence, delivered across Redcentric’s managed IP network. The service is suitable for organisations that have PBXs capable of supporting direct IP connectivity and who want to run both voice and data services via a single converged network connection.

Genius Networks Logo

Genius Networks

Genius SIP connects your site directly into the Genius Network via an IP connection to carry and terminate your inbound and outbound voice calls across the public telephone network. The service is compatible with all leading IP PBX brands and can support connections from two channels for businesses with small PBXs to no limit on the number of channels that can be supported for large enterprises and contact centres.

Voipfone Logo


With Voipfone, SIP trunks are free and unlimited. If you need more calls, you buy more bandwidth. With Voipfone the number of simultaneous calls (old fashioned lines) you can send us is limited only by your bandwidth to us.

Spitfire Logo


Spitfire is an interconnected operator and Internet service provider. The company provisions its own SIP trunk services over its own Internet and Voice networks to provide a complete managed end-to-end solution.



The Orbtalk business SIP trunk service is built on the company’s own VoIP platform. With Orbtalk SIP trunking, you can retain your existing telecoms equipment while benefitting from IP Telephony. Orbtalk routes its SIP trunks with Tier 1 carriers to ensure call quality. Orbtalk SIP trunks support a wide range of hardware PBX's and IP handsets.

BT Logo


BT SIP Trunk runs over BTnet, a dedicated Internet access circuit. That means it only runs over the parts of the infrastructure controlled by BT. The company offers Quality of Service (QoS) that prioritises voice data across your connection and the BT network to deliver quality calls.

Nextiva Logo


Nextiva SIP Trunking supports communication between a local PBX and Nextiva’s SIP Trunking server. This service gives the local PBX a connection to worldwide call routing through Nextiva’s infrastructure.

Compare SIP Trunking Quotes Today

The information on this page should give some insight into what you can expect to find with the SIP Trunking process. If your business is looking to upscale operations, then it might be that you want to look into getting quotes - Approved Index can help here.

We use your specifications to find the most suitable supplier for your business. Simply complete the form at the top of this page and we’ll send you quotes from up to 4 suppliers.

Approved Index’s quote comparison service is free, quick and easy, and it could save you as much as 40%.

Let Approved Index help you find the best SIP Trunking quotes for your business.