hi, I'm testing the arbiter of an especial switch by streaming and playing a video on 2 ports.I need a software to measure the delay and quantify it. The application I have used is VLC player. I could do the streaming test by setting only the RTP protocol on VLC. But when I play the video on another PC and capture the packets by Wireshark, I could see UDP packets, and I can't measure the delay! Is it valid to decode UDP to RTP by wireshark? Doesn't it affect on the accuracy of my test? Thanks, asked 28 Apr '13, 03:58  nice_star2008 |
One Answer:
Do you want to measure the delay produced by the 'special' switch? If so, you would have to capture the packets with a TAP on the incoming and outgoing port of the switch. You should not use a mirror port on the switch, as that might tamper with the results. HOWEVER, unless that 'special' switch is kind of broken, I don't think you will be able to measure any delay (created by the switch), as the accuracy of the time source of the capturing device might not not be good enough to detect any such delay.
Well, it depends what has been transmitted. If those UDP packets are indeed RTP packets, then it's 'save' to decode those UDP packets as RTP (right click and choose "Decode As"). Regards answered 28 Apr '13, 10:40  Kurt Knochner ♦ edited 28 Apr '13, 10:52 |
Thank you so much in advance Mr. Kurt. I am testing the Reference switch of NetFPGA. It has a Round-Robin arbiter for servicing the ports. I'm going to stream a video (real-time packets) on one port, play it on another port and measure the delay between this sending and receiving to test the QoS. If the Qos is not acceptable, I should change the arbiter, reprogram NetFPGA and measure the delay again. What do you mean by TAP? How should I determine the kind of packets? Are video packets indeed RTP packets?
Thanks
see here: http://wiki.wireshark.org/CaptureSetup/Ethernet#Capture_using_a_network_tap
I would recommend to use two TAPs for your requirements. But if you don't have a TAP at hand, you can start with two mirror/monitor ports on the switch.
However: you can't fully trust that setup, unless you know very well how the switch handles those mirrored packets and how much delay is added by the port mirroring!
That depends on the streaming method.
Hard to tell without a sample. Can you please post a small sample file somewhere (google docs, dropbox, cloudshark.org. BEWARE privacy issues!!)