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<tt>Hi Gianluca and all others,<br>
<br>
I am facing a major latency problem on *long lasting* capture sessions
which maybe <br>
has to do with timestamping by the driver, every hint to solve it is
appreciated:<br>
<br>
We developed a proprietary protocol to configure, manage and monitor <br>
our self-developed hardware, the config software uses WinPCap to
capture and send raw packets.<br>
<br>
Everything is working fine, but after some days of continuous capturing
i face:<br>
- On some machines, the latency between sending requests and receiving
the answer <br>
increases to some seconds (can be up to >30 secs after capturing
for a week!)<br>
Closing and re-opening the driver would solve the problem, but i
definitely need to capture<br>
for months and longer without interrupt!<br>
<br>
I know that the driver timestamp is drifting apart from the System
Time(which can be<br>
synchronized by e.g. a NTP server), therefore i timestamp the frames my
myself(which <br>
is also important if a use timeouts)<br>
<br>
<b>My question is:<br>
What could be the reason(s) for huge latency on long lasting captures?<br>
</b></tt><tt>I know that the latency increases on receiving packets<br>
</tt><tt>Currently i don´t know if sending´s latency also increases<br>
Maybe it has something to do with the GetSystemTimeAdjustment setting?<br>
</tt><br>
<tt><br>
Thanks for reading<br>
<br>
Best regards from Austria<br>
Helmut<br>
<br>
</tt><br>
Gianluca Varenni schrieb:
<blockquote cite="mid:6F714BE698B847B883BAC7EB155685EC@NELSON3"
type="cite">
<pre wrap="">The return value of QuerySystemTime and QueryPerformanceCounter is
synchronized at the beginning of the capture (to compute the offset between
epoch time and QueryPerformanceCounter), and then the counter and frequency
returned by QPC are used to compute the number of seconds (and microseconds)
and added to the offset.
The timestamping code is available in the source code of WinPcap,
winpcap\packetntx\driver\time_calls.h
Have a nice day
GV
--------------------------------------------------
From: "Jan Martinec" <a class="moz-txt-link-rfc2396E" href="mailto:martij12@fel.cvut.cz"><martij12@fel.cvut.cz></a>
Sent: Tuesday, September 14, 2010 7:23 AM
To: <a class="moz-txt-link-rfc2396E" href="mailto:winpcap-users@winpcap.org"><winpcap-users@winpcap.org></a>
Subject: [Winpcap-users] timestamp
</pre>
<blockquote type="cite">
<pre wrap="">Hello!
I've got a question about timestamping method. I know that a timestamp
is got using method QueryPerformanceCounter (resp.
keQueryPerformanceCounter), which is a number of ticks of Performance
counter. But timestamp is by Winpcap returned in "Seconds since Epoch"
format. So how is the recomputation done?
Thank you very much
Best regards,
Jan Martinec
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