A Session Initiation Protocol (SIP) trunk service connects a business’s telephone system to the traditional public telephone network via a dedicated IP connection, such as ADSL or an Internet leased line, for making and receiving multiple concurrent telephone calls.

SIP trunking provides your organisation with many benefits including added flexibility and improved business continuity and also offers substantial cost savings over traditional telephony services.

SIP trunks are provided at a lower rental charges than other standard analogue (PSTN) or digital (ISDN) telephone lines plus have the added benefit of greatly reduced call charges and free calls between company sites.

SIP trunks can be provided very swiftly and existing geographic numbers can be retained. As SIP numbers are attached to IP addresses, they have no geographic restrictions and can be routed to any location where an IP connection is available. This means that if a business needs to relocate, or for continuation of business in the event of fire, flood, etc. the published number can be transferred seamlessly without loss of service.

The non geographic nature of SIP trunks also mean that their numbers can be used from a marketing perspective to create a local presence or national. For example, a business could have an Exeter dialling code number even if it is based in Leeds.

When considering a SIP trunk installation, it is important to consider the technical and cost merits of the various IP connectivity options available as the service it is only as good as the connection used to deliver it. SIP is often offered over broadband links which by definition are not carrier class and it would be a brave business manager who committed all of his voice communications to such a technology.

The call quality, the number of simultaneous calls required and the expected resilience should all be considered.