Basic Tools for Vo. IP Troubleshooting (Part 1)As more businesses move towards Vo. IP implementation, information about Vo.
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IP protocols (SIP, RTP, etc) and Vo. IP calls troubleshooting are in high demand.
Voice over Internet Protocol (VoIP) is the name given to technologies and products that allow voice communication over IP networks. Some people consider VoIP as an.
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In this series of blog posts I’ll go over some basic tools useful for troubleshooting Vo. IP calls. I hope that this post will be useful for people who are already working on Vo. IP network and troubleshooting call flows. It should also provide a good starting point for people new at Vo. IP troubleshooting. As we know SIP (Session Initiation Protocol) is a key protocol of Vo. IP calls. Basic knowledge of SIP is a pre- requisite of any Vo.
IP call troubleshooting. There are some good books and online resources available to gain knowledge of this protocol.
I’m going to focus on the basic tools required for Vo. IP troubleshooting and will give you some tips based on my experience working with them. There are a wide varieties of tools available; I’m going to go over a few them that I have personal experience with as I use them every day.
Let’s start with a very important tool required for troubleshooting Vo. IP calls, the packet analyzer. Protocol analyzer: Anyone who works to deploy/design/maintain IP networks uses Protocol analyzer every day.
The tool is more critical for a Vo. IP engineer who is looking to troubleshoot or understand Vo. IP call flows. There are many protocol analyzers available in the market. My favorite is Wireshark (previously called Ethereal). This is very easy- to- learn open- source packet analyzer and the best thing about it is that it’s free.
You can download it for most of operating systems. Here are few key features related to Vo. IP that you can find in Wireshark: This is one of the key features. It’s very helpful for troubleshooting Vo. IP calls. If you open a raw packets dump file, it can not only decode SIP packets from it but also correlates SIP packets and prepares a list of Vo. IP calls. You can find this feature (in recent release 1.
Telephony > > Vo. IP Calls menu. The good thing about this feature is that you don’t have to go through many packets to figure out which SIP message belongs to which call. It does that work for you. Not only that but when you select a call leg listed under ‘Vo. IP calls’, it creates a ‘ladder diagram’ for that call leg. If you select more than one call leg then it will show each leg in its own color in a ladder diagram which makes it easy to distinguish call legs from each other. It might seem simple but it’s very helpful.
The ladder diagram helps to visualize call flow. Different colors scheme for each call leg in ladder diagrams eliminate worries about checking SIP messages to make sure they belong to correct call by checking call- id, From Tag, To- tag, etc. You can also highlight any SIP message in ladder diagram and it will find that SIP message packet in the original packet capture file. That way you don’t have to comb through many packets to find the correct packet.
Another valuable feature is ‘Player’. Once you’re at the ‘Vo. IP calls’ window, select a call leg and click ‘player’ (as shown in screen shot).
It shows you the RTP stream for that call leg. You can play back that RTP stream too. It’s a very useful tool when you are troubleshooting audio issues. One limitation of this feature is that by default it only supports G. There might be way to make it decode G. I haven’t tried it yet.
Last but not least. This might be a very common feature in packet analyzers but what I found very helpful in Wireshark is that it has easy filter syntax.
Intuitive filter syntax helps to create complex filters and helps to clear unnecessary packets from capture. Here are some examples of how people use Wireshark: Network administrators use it to troubleshoot network problems. Network security engineers use it to examine security problems. Developers use it to debug protocol implementations. People use it to learn network protocol internals. These are some basic and useful features of Wireshark protocol analyzer for Vo. IP call troubleshooting.
I personally give this tool 4. Let me know in comments if you find any other ‘must know’ features of Wireshark or your ‘wish list’ features for Wireshark.
In my next blog I plan to cover another very important tool, SIPP call generator for Vo. IP troubleshooting. Please Like, tweet and +1 this post using the buttons above left.
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