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Ask Professor Phil

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Sniffers & IP Video Network Troubleshooting

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Dear Professor Phil,
One of our network technicians wants to place a sniffer on our IP video network to try to troubleshoot some problems that we’ve encountered. What is a sniffer? How can it help solve a video issue?
Sandy, Hershey, PA

The term sniffer has become the generic name for a packet analyzer or protocol analyzer. Like aspirin, it has been a popular brand name. Tens of thousands of network technicians use Wireshark, a cost-free and excellent example of such a program. Commercial protocol analyzers range from no fee to hundreds of thousands of dollars. Sniffers do basically three things: capture data packets, decode each byte of header and data in the packets, and facilitate the analysis of the meaning of the data traffic those packets represent.

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Packet analyzers can help understand many aspects of a video network. They can help diagnose addressing issues and errors, such as dropped packets. They can determine protocol behavior and network efficiency. For example, Wireshark can help you to see how much load your video is adding to the network, if the codec is creating the correct video format (such as H.264 or MPEG-2), and whether or not there may be interfering traffic.

One thing to be cautious about is that most protocol analyzers only decode some forms of video, even when the video is carried by IP. Wireshark and other commercial products decode mpeg transport video, commonly used in IPTV. But, most analyzers have limited use with streamed video that could be encoded by a streaming server. They also provide limited information about YouTube, Netflix, and other video obtained by using a browser.

Dr. Phil Hippensteel has spent more than forty years in higher education and now teaches at Penn State Harrisburg.