Disregard my reply. I confused this thread with the other one related to strange reception delays.
Have a nice day GV From: Gianluca Varenni Sent: Wednesday, September 22, 2010 9:51 AM To: [email protected] Subject: Re: [Winpcap-users] timestamping and huge latency He is measuring the delay between two consecutive packets. Lack of sync between transmitter and receiver clocks would not cause those delays. GV From: "Fish" (David B. Trout) Sent: Wednesday, September 22, 2010 3:30 AM To: [email protected] Subject: Re: [Winpcap-users] timestamping and huge latency Another thing: if the sending and receiving/capturing systems' clocks are not synchronized with each other, then how are you measuring the supposed latency between sending and receiving/capturing? That is to say, if the two clocks are not synchronized with one another, then normal clock drift would completely invalidate your measured latency in my opinion. Are the two system's clocks synchronized with one another? If they're not then there's your answer. p.s. if/when you do synchronize them with each other, remember to ensure that either: a) neither or them synchronizes with an external clock, or: b) only ONE of them does! (but not both!) The same rule applies to the Windows Time Service too: disable it on both or else ensure the one with it enabled is configured as the "time server". Otherwise your results would once again be completely invalid/inconclusive. -- "Fish" (David B. Trout) [email protected] From: [email protected] [mailto:[email protected]] On Behalf Of Helmut Vaupotitsch Sent: Tuesday, September 14, 2010 9:18 AM To: [email protected] Subject: [Winpcap-users] timestamping and huge latency Importance: High 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 dayGV --------------------------------------------------From: "Jan Martinec" <[email protected]>Sent: Tuesday, September 14, 2010 7:23 AMTo: <[email protected]>Subject: [Winpcap-users] timestamp Hello!I've got a question about timestamping method. I know that a timestampis got using method QueryPerformanceCounter (resp.keQueryPerformanceCounter), which is a number of ticks of Performancecounter. 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 [email protected]https://www.winpcap.org/mailman/listinfo/winpcap-users _______________________________________________Winpcap-users mailing [email protected]https://www.winpcap.org/mailman/listinfo/winpcap-users -- ----------------------------------------------------------------Ing. Helmut Vaupotitsch Phone: +43 (0)3133 3780 16ITEC Tontechnik und Fax: +43 (0)3133 3780 9Industrieelektronik GmbH E-mail: [email protected] Lassnitzthal 300 URL: http://www.itec-audio.com---------------------------------------------------------------- -------------------------------------------------------------------------------- _______________________________________________ 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
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