How the SIP protocol works

The SIP protocol is used in voice over IP or VoIP calls. This allows two users to connect with each other and make a communication. We are going to explain how it works, what is needed for it and also the uses that IP telephony has today. A review of the most important of this protocol.

What is the SIP protocol?

In order to communicate on the Internet , to be able to connect to the network or use any of the many services and platforms that exist, it is necessary to use different protocols. This will allow that connection to be established or be able to use a certain program, for example. We are talking about protocols such as HTTP, TCP, IP, FTP… In this case SIP is a protocol related to VoIP.

Its acronym comes from Session Initiation Protocol , which in Spanish can be translated as Session Initiation Protocol . It will allow to establish a communication between two computers and thus be able to establish a communication through an IP network, together with two other protocols: SDP and RTP / RTCP.

The first one, the SDP protocol, stands for Session Description Protocol and is responsible for establishing the parameters for multimedia exchange. RTP, for its part, stands for Real Time Transport Protocol or Real Time Transport Protocol. What it does is define a package for sending audio and video, something necessary in communications.

It basically consists of the SIP protocol allowing two users to communicate with each other. It will allow to establish a communication by voice or video for example between two users using a computer. It is responsible for establishing the location, availability or resources used.

This protocol is not limited to allowing audio input, as it would be for a voice call, but it also allows the transport of videos or messages. Among other things, it is responsible for knowing if a user has already established a call previously and, therefore, is busy.

How the SIP protocol works and what is needed

The operation consists of establishing this communication between two computers . But this protocol simply ensures that communication is possible, since it is not a program by itself or a device as if it were a telephone.

So what do we need to make the SIP protocol work? It is essential that there are a series of points so that communication can be established and function properly. If any of this fails, we would not be able to make a VoIP call.

Internet connection

The first and foremost thing is that there is an internet connection . Without this, communication cannot be established and therefore we cannot use the SIP protocol or any program that relies on it to make a voice or video call.

Ideally, that Internet connection is of quality. The higher the bandwidth, the better. After all, for communications of this type to be of quality, they will require a greater consumption of resources. If we can connect by cable, better than by Wi-Fi.

SIP account

It is also essential to have a SIP address . We are going to have to contract this account with a telephone service. This can be both free and paid and it is usually enough to register via the Internet.

This account will be necessary to be able to communicate with other users. It is basically like having a phone number or an email address. It is needed to know who we are contacting and in what way. We will have to share this address with the other person, in the same way as if we were giving them the mobile phone number.

Two compatible devices

Another basic point is to have devices that are compatible . When establishing communication between two users, it is essential that each of them use a device that allows the use of the SIP protocol and is correctly configured for it.

We can name computers, mobile phones or IP phones, for example. They must have a speaker and microphone, as well as a video camera in case we want to make video calls.


Beyond the hardware, it is also necessary to have software that allows us to communicate. These programs are usually provided by the service that we are using. We install it on the computer, for example an application for computer or mobile, and in this way we can initiate communication.

The software is essential. It is as if we wanted to use e-mail without having an application to start the account or enter the page to be able to send and receive e-mails. The same happens with the SIP protocol, which will need us to install an application.

Uses of IP telephony

What can we use IP telephony for? We are going to show the most common uses and their advantages if we compare it with normal telephony, for example. It offers users a series of possibilities that may be interesting for private use and also for companies.

Be able to make multiple calls

One of the main advantages is that IP telephony allows you to answer multiple calls at the same time. This avoids waiting when it comes to having to take a call from one user and have others in the queue.

This is so since it does not depend on a wiring, as it would happen with a traditional telephone call. In this way we can handle various calls without affecting the quality.

Cost savings

The cost savings are also evident . It is not necessary to have so many devices, such as telephones, since we can use it on computers and mobiles. It will simply be necessary to have an Internet connection.

In addition, another cost reduction has to do with the calls themselves. Especially for a company that needs to make international calls, if we compare it with traditional telephony, the difference is important. We can call anywhere without worrying about its cost.

Use anywhere

Precisely being able to use this technology from anywhere is another advantage. We are not going to be tied to a physical place, as it would be in the case of landlines. We can connect and make VoIP calls from anywhere as long as we have an Internet connection and a compatible device.

This is very interesting for example for remote work. Employees can make calls during their working hours without having to be physically at the company. The same as if they had to be traveling to another place.

In short, the SIP protocol is used to establish VoIP calls. This has advantages over traditional telephony, as we have seen. Basically it will be necessary to have an account, a compatible device, an installed program and an Internet connection.

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