Understanding The SIP Protocol

Understanding The SIP Protocol

SIP Protocol

The SIP protocol can be complex to understand, yet its role is significant in the operation of IP telephony. It will, for example, allow you to connect the VoIP telephony to conventional telephones. To better assimilate the term SIP, it is necessary to understand each aspect fully. For this, let’s study each of the elements that make up its name.


First, let’s define what a protocol is. Commonly, it is a set of rules and guidelines. These rules are defined for each step and process during communication between two or more network systems in telecommunications. For this communication to work, the protocol ensures that the receiving device fully understands the signals received by the sending device.

Finally, it serves as an arbiter between these two systems to ensure they follow the same rules. Some of these protocols are very familiar to us, although we pay no attention to them. We can note the HTTP protocol, which allows communication between web servers and browsers. In the case of SIP, the protocol enables communication systems to make calls, send messages or take part in a videoconference.


Rest assured, it will be more intuitive to define the term session. In telecommunications, a session can be qualified as the period devoted to exchanging data between two devices. Also called signalling, it can take the form of simple voice communication between two telephones or a videoconference combining voice, video and document sharing. It has a beginning and an end when the communication is over.


Since we are talking about a period, initialization is starting something. Therefore, to open a session, it is a question of initiating it. Once the caller launches the protocol, it will verify that the receiving device is online and ready to receive the communication. Thus, when your interlocutor picks up, we will talk about initialization. However, SIP goes beyond simple session initiation, and it will take the form of a cycle to establish it, maintain it and close it.

What Does The SIP Protocol Handle?

This protocol is part of a more extensive system, IP. As such, it does not handle all aspects of communications. Mainly, the SIP will manage these five functions on an IP network:

User location

First, when you initiate communication, the SIP will determine the recipient’s location. This will allow him to respond to your request, whether a call or a message, regardless of his location.

User Availability

Then, the SIP protocol will look at the willingness of your interlocutor to respond to your communication. This allows you to know if it is online or available.

Technical capacity

The SIP will also manage the technical capacity of the user. The protocol will ensure that it has a device capable of receiving specific types of media such as video, for example.

Session settings

What we call session settings is simply the ringtone. The SIP takes care of ringing both the caller and the called party using a previously defined ringtone.

Session management

Finally, session management includes:

  • Transferring and terminating sessions.
  • Modifying session parameters.
  • Setting up actions during the call, such as video conferencing or document sharing.

To summarize, if we follow each step of the protocol, the SIP verifies that your interlocutor is in a place with sufficient network coverage and is available. After that, he will ensure that his device is technically compatible with the request sent. Once all these steps have been completed, the SIP rings the device, and the communication can begin. Finally, it allows you to perform all sorts of actions during this communication.

The Application Of The SIP Protocol In Telephony

SIP Trunking

SIP Trunking is very important in the PBX system. SIP trunking, which corresponds to SIP trunking, allows you to connect a VoIP architecture to conventional telephones. We can say that the SIP trunk is the virtual version of the analog lines. Moreover, the advantage of this solution is crucial. It allows you to maintain your old classic telephone and VoIP systems.

Thus, a SIP provider can connect as many channels as you want to your PBX so that you can make calls over the Internet. And, if you already have a PBX in your company, it can connect to it and allow you to make outgoing calls on your existing system without restrictions on the number of simultaneous calls.

SIP forwarding

It will allow users to integrate their own carriers and numbers into a new phone system.

Also Read: Transit IP And Peering, The Basis Of Internet Service

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