Wireshark-users: Re: [Wireshark-users] frame loss

From: Hansang Bae <hbae@xxxxxxxxxx>
Date: Tue, 11 Mar 2008 20:21:16 -0400
Fabiana moreno wrote:
I'm streaming a video and i want to know how many frames i have lost when streaming.

How can i find out how many frames i have lost when doing a capture?

I know the same timestamp means same frame..

So when i have incorrect timestamp or wrong sequence in rtp analysis this mean that the frames are lost?


streaming video usually denotes UDP, so you can't do sequence number analysis. However, there are clues that you can use to find missing packets.

1) Look at the IP ID field. Do they increment uniformly? They may not if the publisher of the stream is servicing more than this one stream. But if you're lucky, it may increment by one, or by two. If all of sudden they increment by two or four (respectively), then you may have lost a packet.

2) See if the streaming server puts any identification within the packet itself. You may be able to find a few fields that are incrementing uniformly. Again, it may be a clue as to how the packets are "timestamped" for application tracking. By timestamp, I mean a counter and not the packet's absolute capture time.

3) This may be the most reliable (but not scalable) way. Capture at the publisher and some consumer. See if the same number of packets are captured on both sides.

Unfortunately, for case #3, the old rule of engineering kicks in: you can have it fast, cheap, or reliable. You can have any two, but not all three.

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Thanks,
Hansang