How To Capture SIP Packets

How To Capture SIP Packets

SIP Packets CaptureFor all those IT team members managing VoIP communication systems for their organization, things can become a little challenging. There are several instances of calls dropping after a few seconds or the audio turns one way while calling to specific numbers. Getting the hang of the real problem behind these issues and troubleshooting can be extremely challenging. You might find that the config files are absolutely fine, yet the calls still behave in a weird manner. In this blog, we are going to take a look at one of the most interesting and helpful tools that can help you identify and fix the bugs that affect the call flow in your VoIP communication system – SIP packet capture tool.

SIP Packet Capture is one of the most useful tools available in the market that helps make VoIP communication maintenance a breeze. It is the norm for the VoIP system to have log files for all the calls that are made or received. This is extremely effective in tracking bugs in the system and fixing them. However, logs can turn a bit confusing for situations where no call data are registered in the log files or you still connect to an unknown error recording even for the call data in the log files. This is just the perfect situation when you would require something like SIP Packet Capture tool that cannot only help you to identify the errors but at the same time fix any other issues bugging the system.

Packet captures are the efficient tools that help you to capture the raw packets sent from and received by the system. Data packets are the only way to transmit information over the Internet or any other digital network. These data packets contain bits of information that are processed and compiled together when they arrive at their specific destinations. In a similar manner, the VoIP signals too are transmitted in the form of small SIP packets along with the call parameters and the media stream that would contain the audio files. If you are able to capture these packets then you will come to know what is actually going wrong and fix the issues accordingly.

The majority of the VoIP systems have some form of SIP packet capture included in the package but its version and features will vary from one to another. For the systems that are operating on Linux, you can use the tcpdump command to capture the SIP packets. You will need to have a direct command access to the phone system by using the SSSK or the monitor and keyboard plugged to the system. The following command will get things done:

tcpdump -s 3000 -w ~/capture-file.pcap port 5060 or portrange 10000-35000

In case your system wants permissions then you can add “sudo” at the front for running the command with the root permissions. Once you have captured the SIP you can go ahead and place a call. Now, tcpdump is working in the background and writing the packets on to the designated files. Thus, when you have all the call records from the SIP data packets, you can drill down and find what’s actually causing all the problems.

Captures are the actual SIP packets and they all follow the same coding language all over the world. Thus, you will be able to take a closer look and identify the problems before completely eliminating the issues. Learning how to capture the SIP packets is not a very challenging task and with a little dedication, you can make your VoIP maintenance job extremely easy.

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