What is SIP Trunk (Session Initiation Protocol Trunk)?

This page informs you about what a SIP trunk is, and on how you can make use of it. You can read about SIP and trunks, and about SIP trunks in general. After this, there is a short description about the things you can have as a SIP trunk user.

A SIP trunk is a type of connection that is able to manage several types of data (video, voice, text, etc.) in the same time. By using the SIP protocol and VoIP technology, able to establish connections via the Internet.

As you can see in Figure 1, the VoIP phones are connected one by one to the Ozeki Phone System server with a SIP trunk. The Ozeki Phone System server is also connected to the Internet with another SIP trunk. With these connections, the VoIP phones can make calls that go through the server and the Internet. Via the Internet, even international calls can be made with an extremely high quality and reliablity. For this the Ozeki Phone System is a necessary tool.

sip trunk
Figure 1 - SIP Trunk

The SIP trunk is a product of VoIP service providers. It is primarily designed for enterprises or call centres to manage many phone lines in the same time. In order to acquire the SIP trunk, you have nothing else to do but to order a SIP trunk service from a VoIP service provider.

SIP, Trunks and Trunking

The SIP protocol or Session Initiation Protocol has a role in building up and disconnecting calls. SIP is to set up real-time multimedia sessions between the two or more endpoints of the communication. With SIP, users can chat, make audio and video calls and have online conferences.

A trunk, similarly to the trunks of the trees in nature, is a line or link constructed to handle many signals simultaneously. It also connects major switching centers or nodes in a communication system. It's like the body of the trees connect the roots and the branches. The data transmitted by trunks can be voice data, computer programs, images, video or control signals.

The use and management of trunks is trunking.

Using SIP Trunk

SIP trunks are necessary when there are numerous phone calls in the same time. In the case of call centers and individual VoIP phones that should have more than one call simultaneously.

When you order the SIP trunk from a VoIP service provider, you should ask it to be connected to your Ozeki Phone System server. This is the VoIP PBX that is going to manage the calls. The proper management of trunk calls can only be made through a server, so through the Ozeki Phone System.

After you have got your SIP trunk lines connected to the Ozeki Phone System server, you can work with your devices according to these:

  • when you are using a phone, it will indicate the new incoming call instead of automatically refusing the new caller

  • you can change your call partners during a phone call and make the other ones hold the line until you change the call back on them

  • in the case of call centers, several, maybe hundreds of calls have to be managed simultaneously

With SIP trunk lines users can:

  • make and receive local and long-distance calls even simultaneously

  • use desktop, mobile telephone devices and Ipad

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