IP-PBX and hosted PBX systems work in two very different ways from a SIP trunking standpoint. Both technologies interact differently with the Private Branch Exchange (PBX), Public-Switched Telephone Network, Internet Telephony Service Provider, and the Enterprise Boarder Element (EDGE).
How SIP Trunking Works (PBX)
Here is a diagram that shows how SIP trunking works. You’ll see that on the left hand side is your Public-Switched Telephone Network. As you move along the communication line and to the center you’ll see the Internet Telephony Service Provider, this is the area where SIP trunking occurs. It is in here that the calls are routed to the correct PBX. Once the call reaches the PBX, the PBX will direct it to the EDGE.
How SIP Trunking Works (Hosted PBX)
This diagram represents a hosted PBX solution. In this case, the company will actually host the PBX server for you. People like the hosted PBX solution because it saves you money on total cost of ownership. Also, you get regular upgrades and can plug right into the Internet. Hosted solutions can also come with additional service offerings.
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