8 Common VoIP Protocols: What They Are and Why They Matter

Since the pandemic, VoIP use has increased by 212%, showing its importance for remote work and the future of communication.

However, a key element ensures VoIP works well and continues to grow: VoIP protocols. VoIP protocols are the foundation of a building: you don’t see them, but they are vital to keeping everything stable.

In this article, we’ll explain what VoIP protocols are, highlight the 8 most common ones, and discuss why they matter.

Key takeaways:

• VoIP protocols are tools that allow voice transmission, video, and data over the internet, ensuring calls are conducted smoothly and securely.
• Common VoIP protocols include SIP for starting and managing calls, RTP for real-time data transmission, and SRTP for encrypting communications to protect privacy.
• VoIP protocols are crucial for ensuring efficient, secure, and high-quality communication. They prevent issues like dropped calls, poor audio/video quality, or security risks.

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What Are VoIP Protocols?

VoIP, or Voice over Internet Protocol, is a technology that lets you make voice calls over the Internet instead of using traditional phone lines.

However, VoIP technology needs a set of rules called VoIP protocols to work smoothly and securely.

Imagine you’re sending a letter: you need to follow specific rules to ensure it gets to its destination, such as including the correct address, using an envelope, etc. VoIP protocols work similarly but for calls over the Internet.

Therefore, VoIP protocols are the tools that let you make calls, send messages, or hold video conferences over the Internet. Thanks to them, these messages are sent quickly and effectively.

The Core Functions of VoIP Protocols

VoIP protocols define the rules and steps software systems must follow to transmit data for making a voice call over the Internet. Here are their main functions in a VoIP call:

• Describes media: They determine which media types (audio, video, text) will be sent during the call.
• Connects management: They establish the call or connection between the people speaking.
• Signals: They identify each person’s location, dial the number, agree on the type of voice or video format to be used, and control features like muting or transferring the call.
• Transports: They ensure that both sides of the call can send and receive data correctly and reliably.
• Guarantees security: To protect the calls, they verify the identity of the users, encrypt the data to safeguard privacy, and ensure that unauthorized people cannot listen to the call.
• Controls quality: VoIP protocols work like quality inspectors, ensuring clear communication and monitoring it during the call.

What Are the Most Common VoIP Protocols?

#1 Session Initiation Protocol (SIP)

SIP is a popular protocol because it’s used for more than just Internet voice calls (VoIP); it’s also used in online games and messaging apps. 

For example, when you make a video call on your smartphone or send a voice message in a chat app, SIP often works in the background to set up and manage the connection.

Think of SIP as the VoIP coordinator—it starts, manages, and ends calls. It lets you call on your existing devices without upgrading or replacing them.

#2 Real-Time Transport Protocol (RTP)

After SIP connects the callers, RTP takes over to handle the real-time transmission of data, such as voice during a call or video in a video conference. It’s like a speedy delivery service, quickly sending data to avoid any delays in live communication.

For instance, during a video conference, RTP makes sure the audio and video are sent smoothly and stay in sync, allowing the conversation to flow naturally without lag.

#3 Real-time Transport Control Protocol (RTCP)

RTCP works alongside RTP to ensure good call quality. It acts like an “inspector,” checking how data is transmitted by monitoring the number of data packets, any data loss, and the time it takes to arrive. This information is crucial for troubleshooting connection issues and improving call quality.

For example, if you notice that the audio is cutting out or the video is freezing during a call, RTCP steps in to help address these issues.

#4 Secure Real-Time Transport Protocol (SRTP)

SRTP is a security protocol that protects calls by encrypting data and ensuring it remains untouched. While not always required, you can turn on SRTP for extra security to prevent attacks or eavesdropping.

For example, if you’re in a video conference discussing business strategies or confidential financial data, SRTP encrypts all the audio and video. 

Therefore, if someone tries to intercept the call, the data will be encrypted and unreadable, keeping the conversation private.

#5 Session Description Protocol (SDP)

SDP works alongside SIP to exchange basic information about the call, such as the users’ names, the type of audio or video to be used, the start and end times, and other technical details.

Imagine two employees at a company, John and Emily, who are having a video call to discuss a project. The company uses an internal VoIP system for all its communications. 

In this example, SDP would exchange information like:

• Session Type: Project video call.
• User Name: Emily Smith (initiating the call).
• IP Addresses: Internal IP addresses are used to connect both devices.
• Port: The port number through which the call will be transmitted.
• Video and Audio Format: The agreed formats for the call (H.264 video, AAC audio).

#6 Media Gateway Control Protocol (MGCP)

Some VoIP calls need to switch from the Internet to a traditional phone network. MGCP handles it by converting the call data from a digital format (used online) to an analog format (used by traditional phones).

Simply put, MGCP works like a translator, helping calls connect smoothly between the internet and traditional phone networks, making communication possible between both.

For example, imagine a sales agent needs to contact a client who has a landline phone. The agent would dial the number from their VoIP application (Internet call) on their computer so that the call would travel in digital format.

When the call moves from the internet to the traditional telephone network, MGCP comes into play. It takes the call in digital format and converts it into an analog signal that traditional phones can understand.

Thanks to MGCP, the sales agent’s call reaches the client’s landline as if it were a regular call, allowing smooth communication between them.

#7 H.323

H.323 is an older protocol that was used to transmit audio, video, and data over the Internet. It was easy to use, but SIP is now replacing it because H.323 is difficult to adapt to new changes and technologies.

However, H.323 is still used in some telecommunications systems, especially with older equipment. Although it’s not as popular as it once was, it remains useful for connecting communication systems that have not been updated to newer protocols like SIP.

#8 Jingle

Jingle is a VoIP protocol used in messaging apps to allow voice calls, video chats, and other real-time communication. It works specifically with XMPP networks, commonly used for instant messaging. Jingle was used in apps like Google Talk (when it was still around), but it’s not as widely used as other VoIP protocols like SIP.

For example, if a company uses an XMPP-based messaging platform for internal communication, Jingle lets employees send text messages, make voice calls, and hold video conferences from the same app without switching to another platform.

Improve Your VoIP Calls with Key Protocols

We’ve learned that VoIP (Voice over Internet Protocol) protocols are crucial for fast, safe, and high-quality communication over the Internet. Each protocol has a specific role, from setting up the connection to maintaining call quality and securing the information being sent.

As a final tip, to improve the quality of your VoIP calls, use protocols like RTCP, which monitor transmission quality, and use these 10 proven strategies to enhance your calls.

Sources

• 12 Most Important VoIP Statistics