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<DIV><FONT face=Calibri>Do you measure the latency by looking at the WinPcap
timestamps or at the timestamps that you generate? How do you measure such
latency?</FONT></DIV>
<DIV><FONT face=Calibri></FONT> </DIV>
<DIV><FONT face=Calibri>Have a nice day</FONT></DIV>
<DIV><FONT face=Calibri>GV</FONT></DIV>
<DIV style="FONT: 10pt Tahoma">
<DIV><BR></DIV>
<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title=hv@itec-audio.com
href="mailto:hv@itec-audio.com">Helmut Vaupotitsch</A> </DIV>
<DIV><B>Sent:</B> Tuesday, September 14, 2010 9:18 AM</DIV>
<DIV><B>To:</B> <A
title="mailto:winpcap-users@winpcap.org CTRL + Click to follow link"
href="mailto:winpcap-users@winpcap.org">winpcap-users@winpcap.org</A> </DIV>
<DIV><B>Subject:</B> [Winpcap-users] timestamping and huge
latency</DIV></DIV></DIV>
<DIV><BR></DIV><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 donīt know if sendingīs
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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