Ethereal-users: [Ethereal-users] measuring latency using ethereal

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From: Mark Zvolanek <Mark.Zvolanek@xxxxxxxxxx>
Date: Thu, 20 Nov 2003 17:17:41 +1100
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
Mark.Zvolanek@xxxxxxxxxx