the accuracy of the timestamp depends on the platform you run ethereal on since the timestamps are generated by the system/os and not ethereal.
some platforms have better timestamp resolution than others. I think some versions of windows only provide 10ms or something like that accuracy. some versions of linux can provide sub ms accuracy depending on the CPU and how the kernel was compiled. Even if the individual timestamps are of low resolution, if you take the average and a sufficiently large number of measurement samples, it should all even out and converge to a very accurate timestamp. negative latency, maybe the link is really really fast from time to time? :-) ----- Original Message ----- From: "Mark Zvolanek" Sent: Thursday, November 20, 2003 5:17 PM Subject: [Ethereal-users] measuring latency using ethereal > Hello, > > I am trying to determine WAN link latency using ethereal. I do this by > attaching dual NIC PC to two ethernet segments located accross WAN link and > running on this PC two instances of ethereal each sniffing on different NIC. > Btw, this is done in a lab. TCP packets are sent and received by different > two PC's. > > I am seeing negative latency, for approx 60 out of 6000 packets. I thought > using one PC I would avoid time sync issues. :-( > Eg: source LAN > 16:57:10.375717 10.42.254.50 -> 10.40.8.16 TCP 62 14711 > 3068 [PSH, ACK] > Seq=10004969 Ack=5226877 Win=28888 Len=8 > destination LAN > 16:57:10.370012 10.42.254.50 -> 10.40.8.16 TCP 62 14711 > 3068 [PSH, ACK] > Seq=10004969 Ack=5226877 Win=28888 Len=8 > > What is the accuracy of the timestamp used by ethereal? The PC running > ethereal is Windows XP, Pentium 4 2GHz Compaq. > Would anyone have any suggestions on how to accomplish this? > > Regards > Mark Zvolanek > +612 9227 0479 > [EMAIL PROTECTED] > > > > _______________________________________________ > Ethereal-users mailing list > [EMAIL PROTECTED] > http://www.ethereal.com/mailman/listinfo/ethereal-users >
