sip trunk is a logical connection between an ip pbx and a service provider「s application servers that allows voice over ip traffic to be exchanged between the two.
this paper will explain how to improve the communication of an organization with multiple office locations by using ip pbx, and summarizes the criterion for selection of ip pbx system.
each call consumes a certain amount of network bandwidth, so the number of calls is limited by the amount of bandwidth that can flow between the ip pbx and the provider」s equipment.
the typical ip pbx can also switch calls between a voip user and a traditional telephone user, or between two traditional telephone users in the same way that a conventional pbx does.