VoIP Call Flow: Analyzing SIP Packets With Wire Shark

Have you ever wondered how you transfer your voice and which path you take when making a VoIP call? It is very similar to a covert operation which means that small packets are substituting as spy cars carrying your voice to the general destination.

What is Wireshark, you ask?

 As a command line tool, tcpdump is an excellent feature that allows people to capture and analyse the traffic in the network. Think of it as a high powered security gadget that is able to listen in and even decode a message that is being dispatched across a network.

Let's dive into the world of VoIP and see how Wireshark can help us uncover its secrets:

The INVITE: When you make a VoIP call, your phone sends out an "INVITE" message, saying, "Hey, I want to talk to this person!"

The 200 OK: If the recipient's phone is ready, it responds with a "200 OK," saying, "Great, let's chat!" SDP (Session Description Protocol): This is where the fun begins! SDP tells both phones about the details of the call, like what type of audio codec to use and how to send the data.

BYE: When you hang up, your phone sends a "BYE" message, saying, "That was fun, but I'm out!" Now, let's use Wireshark to see these messages in action:

Capture the traffic: Connect your computer to your network and start capturing packets with Wireshark.

Analyze the packets: Examine the details of each packet, including the source and destination addresses, the SIP headers, SDP payload. With Wireshark, you can:

Troubleshoot VoIP issues: If a call is not working you don’t need to talk to the other person, you can look at the packets and see where the problem is.

 Learn about VoIP protocols: Learn more about the functionality of VoIP and all possible protocols in its use.

 Have fun exploring the digital world: It’s still detective work but in a virtual environment!

Hence, welcome your Wireshark, put on your detective hat and let the journey into the world of VoIP begin!