Do you measure the latency by looking at the WinPcap timestamps or at the timestamps that you generate? How do you measure such latency?
Have a nice day GV From: Helmut Vaupotitsch Sent: Tuesday, September 14, 2010 9:18 AM To: [email protected] Subject: [Winpcap-users] timestamping and huge latency Hi Gianluca and all others, I am facing a major latency problem on *long lasting* capture sessions which maybe has to do with timestamping by the driver, every hint to solve it is appreciated: We developed a proprietary protocol to configure, manage and monitor our self-developed hardware, the config software uses WinPCap to capture and send raw packets. Everything is working fine, but after some days of continuous capturing i face: - On some machines, the latency between sending requests and receiving the answer increases to some seconds (can be up to >30 secs after capturing for a week!) Closing and re-opening the driver would solve the problem, but i definitely need to capture for months and longer without interrupt! I know that the driver timestamp is drifting apart from the System Time(which can be synchronized by e.g. a NTP server), therefore i timestamp the frames my myself(which is also important if a use timeouts) My question is: What could be the reason(s) for huge latency on long lasting captures? I know that the latency increases on receiving packets Currently i don´t know if sending´s latency also increases Maybe it has something to do with the GetSystemTimeAdjustment setting? Thanks for reading Best regards from Austria Helmut Gianluca Varenni schrieb: 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" <[email protected]> Sent: Tuesday, September 14, 2010 7:23 AM To: <[email protected]> Subject: [Winpcap-users] timestamp 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 _______________________________________________ Winpcap-users mailing list [email protected] https://www.winpcap.org/mailman/listinfo/winpcap-users _______________________________________________ Winpcap-users mailing list [email protected] https://www.winpcap.org/mailman/listinfo/winpcap-users -- ---------------------------------------------------------------- Ing. Helmut Vaupotitsch Phone: +43 (0)3133 3780 16 ITEC Tontechnik und Fax: +43 (0)3133 3780 9 Industrieelektronik GmbH E-mail: [email protected] A-8200 Lassnitzthal 300 URL: http://www.itec-audio.com ---------------------------------------------------------------- -------------------------------------------------------------------------------- _______________________________________________ Winpcap-users mailing list [email protected] https://www.winpcap.org/mailman/listinfo/winpcap-users
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