[Winpcap-users] WinPCAP packets capture delay..
alimjankuramshin at gmail.com
Wed Sep 22 06:44:35 PDT 2010
Hello, Gianluca! Thanks for the test and detailed answer..
> Let's step back and analyze the whole issue. Correct me if any of the
> following statements is wrong.
> - You have your custom ethernet hardware that is used to generate packets.
Quite correct, yes..
> - your hardware is able to generate packets at a constant rate, and you can
> prove that the packets are transmitted at a constant rate with an
Yes, i've got access to the good oscilloscope, Lecroy with an several Gs/s..
> - when you use a WinPcap-based app (e.g. wireshark) to capture packets,
> every now and then you see something weird in the timestamps. Instead of
> being all equally spaced, every now and then you see a big gap of some
> microseconds. For example you see 40us, 40us..., 10000us, 40us...
And that is wright. But also, i've notice some interesting thing: sometimes timestamp of the next packet from the delay is toooo small,
for example, i've got, us: .. 43 46 48 42 1500 2 49 41 35 48.. So, 2us difference of time stamps a little bit strange i guess.
> Here are my questions/suggestions:
> - are you sure that NO packets are dropped on the receiver side?
Well, when my device send about 10000 packets NO, no drops, but delay still present. But when my device send a 1000000
packets my laptop/ethernet card or Wireshark drop about 5-10 packets and at the same time connection information from the
network property page of the network adapter show exactly 1000000 packets received for all the test repeats :/
> - when you measure with the oscilloscope, are you 100% sure that you are
> looking at the gap between ALL the packets?
Well yes, i've got not only the TX line signal but some other ethernet controller help signals on the oscilloscope screen (4 channels)
and found nothing strange with any of the test i've done..
> - how are you running your tests? What I would do is the following:
> + have your hardware transmitter generate a fixed number of packets (e.g.
> 1 million). Put an incremental counter in every packet.
> + capture the packets with the winpcap-based app, and make sure that ALL
> the packets are received. If you didn't receive 1 million packets, check the
> incremental counter within each packet.
And at this time You absolutely wright, i've done exactly the same thing and a lot of variation. It is really easy to say what i've don't try :(
> - you say that you encounter this issue on your laptop with XP/Vista/Win7.
> So always the same hardware (and NIC card).
> - Do you see the same exact issue with another PC running a totally
> different NIC board (hint: use an intel one, they are extremely reliable in
> my experience)?
I've tried some PC and laptops, i can't remember really all of the hardware parameters, but card was: BroadCom, Intel i guess and Realtek..
And different OS'es. Not so old hardware ~ 2,66-3Ghz CPU's and huge RAM 4-8 Gb..
My laptop Asus G1S has 2.2 Ghz Intel Core2 CPU unit, 2 G RAM and Realtek 8111B/8168B network card.
> Have a nice day
Well, such a grief i've got :(
Many thanks for Your attention, i am really grateful to you, with many thanks and best wishes, bye-bye..
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