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What Are SIP Trunks?

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The world of business telephony has undertaken a great deal of change over the past decade. This change has seen SIP Trunks become the go-to protocol for VoIP (Voice over Internet Protocol) technology. In this blog, we will explain what are SIP Trunks and look at the reasons why they have become so popular. 

SIP stands for Session Initiation Protocol and is the standard and widely used communications protocol for voice and video traffic in a Unified Communications system on a data network. 

SIP Trunking Explained

A SIP trunk is the connection between an IP-PBX and an ISP (Internet Service Provider) and can use an existing internet connection, rather than requiring its own standalone internet line. It is a virtual connection and eradicates the need for any physical connection to a phone provider.  SIP trunking is essential for setting up communication sessions in the modern business communications world.  

Think of a SIP trunk as the modern replacement of the old copper analogue lines or ISDN circuits that connected an in-house office PBX (Private Branch Exchange) with the PSTN (Public Switched Telephone Network).

A SIP trunk provides greater flexibility and quality of service over existing or legacy phone lines.  SIP (session initiation protocol) is the technology that sets up, modifies and terminates real-time sessions.  This is known as VoIP (Voice over Internet Protocol).

VoIP and SIP work together to provide a solution for the setup and management of calling sessions across the internet.  A service provider will provide Sip trunking and can manage the number of concurrent calls and quality.  As SIP trunks are ‘virtual’ equivalents of traditional analogue or ISDN services and faults can be monitored and corrected by a sip trunk provider without the need for engineer visits and costly outages.

SIP trunking can also be used as part of a Unified Communication (UC) solution providing PSTN access to a UC offering that can support video calls, instant messaging and conferencing features.  Services will depend on PBX type and the UC platform.  UC can deliver more than traditional phone calls and voice calls but the solution can be across multiple devices such as traditional handsets or applications on mobile devices, tablets or computers. UC is also an effective method of providing small businesses with an enterprise-grade phone system.

Why have SIP Trunks become so popular?

The reason for this is two-fold. First of all, it is due to the fact that the internet has become quicker and more reliable. As SIP is dependent on an internet connection, businesses had to ensure their internet connection was capable of supporting the service. With Fibre Broadband now offering speeds of up to 1Gbps, businesses have this assurance and peace of mind.

A further reason is that SIP offers real-world benefits over legacy telephone lines. Not only does SIP offer greater flexibility and call quality, but it also presents the benefits that can be found in the next section of the blog.

Benefits of SIP Trunks

The benefits of SIP trunking over traditional telephony solutions include:

  • Cost Savings – Whilst each provider have their own pricing structures, it is a widely accepted fact that SIP trunks over great savings on call rates versus traditional PSTN technologies, whilst also requiring no upfront capital expenditure. 
  • Scalability and call volume – the number of channels is configured at each end of the SIP trunk and additional SIP channels can be configured in minutes without the requirement for new hardware. This may be dependant on bandwidth available.
  • Reliability is guaranteed and maintenance is quicker and easier as SIP trunks are resilient and easy to re-route in the event of any problems providing business continuity and disaster recovery strategies.
  • SIP trunking provides excellent call quality and different codecs can be used to maximise bandwidth in an existing network. 
  • Existing business phone systems can be migrated to SIP without heavy lifting and expensive costs.  Some older PBXs may require upgrading to support direct SIP trunking.

Frequently asked questions

I’m not ready to replace my PBX but I would like to save money on calls, is there anything I can do?

If your existing PBX does not support SIP trunking an Analogue Terminal Adaptor (ATA) or Gateway can be used to provide a bridge between SIP Trunk and PBX, meaning that all existing functionality is retained.  This allows existing PBX systems with traditional phone lines, analogue ‘landline’ or PRI (ISDN lines) to be used with SIP trunks.   

My business has had the same phone number for years – will I lose it and have to start again?

Existing phone numbers can be ‘ported’ to your SIP trunks, this means that the move to SIP technology will not result in any loss of business or service, no costly alterations to existing number schemes.  Porting is arranged through your Service Provider.  

Can I use SIP Trunks for international calls?

There are no restrictions on calling destinations with sip trunking services and traditional telecom call barring can be applied on the IP-PBX or by the Service Provider, i.e. National and International Calls allowed or barred with support for inbound and outbound services.

For further information on SIP Trunks, visit our dedicated SIP Trunk page, complete the quote request form below or contact us on 01635 884170 or email to sales@stream-networks.co.uk


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