Session Initiation Protocol (SIP)

SIP is one of the key parts of a VoIP phone call. As the name suggests, SIP helps to start the call and can also be used to start video or other media transfer over the internet. SIP will look up the number you have dialed, find the device you are seeking to connect with and establish the connection once the recipient has answered their phone.

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SIP Trunks

SIP Trunks are essentially virtual telephone lines, in that they create a phone line over your internet connection.  A number of our current customers use this technology to create a failover, so that in the event their regular phone line suffers a problem, they can swiftly switch to their SIP Trunk service. Find out more on our Calls and Lines page.
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How does SIP Trunking work?

The route your traffic travels is actually relatively similar to the route that it might take in your current PSTN setup.  Your call will travel via your Internet connection to the Internet backbone where it will be routed. Depending on whether the call’s destination is another VoIP network or a PSTN network will determine the infrastructure it passes through. If it’s heading to a PSTN extension, the call will travel through “gateways” which effectively transfer the VoIP signalling into signals appropriate for the older network, which is why VoIP calls can reach any number and vice versa.  If the call is heading for another VoIP recipient than it’s possible it will travel exclusively over the IP network. That being said, it is common for calls to be switched multiple times between networks to create the quickest and/or cheapest route for the call to be made.