The Session Initiation Protocol (SIP) is the key protocol that supports VoIP (voice over IP) calls. It does so by setting up and tearing down real-time sessions (calls) between two endpoints (phones). SIP trunks therefore use VoIP to enable voice calls over the internet or a data network.

Calls on MTN SIP Trunks are charged at local fixed line rates.

The benefits of using MTN SIP Trunking are:

• Flexibility to use different service providers to achieve Least Cost Routing (LCR) on outgoing calls since you have your own IP PBX.
• Easy and quick scalability as there is no need to add termination hardware when increasing trunk capacity, as is the case with PRI ISDN. Adding or removing extra capacity can be as simple as a configuration change, with the number of available simultaneous calling lines only limited by the available bandwidth.
• Greater cost efficiency than with PRI ISDN.
• Automatic call rerouting to pre-defined locations or to a mobile phone should the location go offline, or in the event of a data outage, allowing for business continuity.
• When the SIP Trunking service is delivered over an internet connection, unused bandwidth can be temporarily used for other purposes.

The bandwidth needed for a SIP Trunk depends on the number of simultaneous calls a business would like to be able to conduct on the SIP Trunk. This can be determined at the time of signing up for the service.