This means that you need some way to connect calls between the internet and the traditional phone network, as otherwise you’d only be able to call other users with VoIP. It’s necessary because VoIP calls travel over the internet rather than the traditional phone network. We’ve mentioned that SIP trunking is a network service. We offer a fuller explanation in our article on the SIP protocol. SIP initiates the sessions (or connections) that prepare the network to best meet the specific needs of a real-time audio connection over the Internet. SIP is an application layer protocol designed to provide a very certain type of road surface for this special traffic. They require audio to be delivered consistently with minimal delay. VoIP-phone conversations over the Internet-are one very particular type of traffic. Some surfaces work better for certain purposes.

The Internet has a wide variety of road surfaces, some favoring certain types of traffic over others: Compare a heavily loaded truck slowly climbing the rough road surface of a hill to a sports car zipping down smooth concrete. SIP is a protocol that operates within the application layer.ĭifferent application layer protocols are used to create different surfaces. The application layer determines the quality of the “road surface” directly above it. At the top, just under the surface, is the application layer. Within the link layer, link layer protocols organize groups of local connections into large networks. One of the lowest layers supporting the Internet is called the link layer. Each layer has its own specific set of languages used to communicate within that layer. These lower layers support-and determine the quality of-the layers above them. Most Internet users only ever see the contents of the vehicles traveling on the roads.īut like real roadways, the Internet has many layers below the surface. On it are many types of vehicles, delivering various-sized packages (or packets, to use the technical term) containing a variety of information at a wide range of speeds. Imagine the Internet as a vast network of roads and highways. What Is the Session Initiation Protocol (SIP)? We’ll explain what SIP trunking is, why you need it, and the primary considerations that you should factor in when deciding on a provider.

While this service is generally included with “per-user” licenses for cloud-based phone systems, if you have an on-premise system you’ll most likely need a SIP provider to connect calls with it. We still need configure “dial plan” to do that.įor example, we want all calls whose called number prefix is “00” should be routed to such SIP server, such as “008613800138000”, etc.SIP trunking is a network service that allows businesses to connect VoIP phone systems to the traditional phone network. We want our outgoing calls to be routed to such peer SIP server/gateway. Please click menu “dial plan / analysis called number” to configure a record to route DID numbers to local users: Please click menu “dial plan / transition” to configure a number transition: We can use “dial plan” to do that.įor example, we want the DID incoming calls whose called numbers prefix is “1234” to local users, such as 1234100 to local user 100, 1234101 to local user 101, etc. Once we receive incoming calls from peer servers, we want to route them to local users. Please click menu “data / peer servers” and add a new record with following information: Step 1: add the server into MSS servers list It is very easy to establish SIP trunk in MSS.įor example, we want to establish SIP trunk with peer server whose domain name is “” and its SIP port is 5060 which is a default SIP UDP port. That means, “external line” is server-to-users mode and “SIP trunk” is a server-to-server mode. The difference between “SIP trunk” and “External lines” is that SIP trunk doesn’t require authorization during the call. For example, in most DID services deployments, SIP trunk is required to send or receive DID calls. In VOIP depolyment, “SIP trunk” is often used to establish a connection with peer sip servers or gateways.

Sip trunk onsip