From: Craig Small (exrwrrif.tppffa@cmles.com)
Date: Tue May 22 2001 - 14:23:25 EEST
On Mon, May 21, 2001 at 11:45:58PM -0500, Chuck Hast wrote:
> Folks I am looking for a way to capture the time of arrival of a ping at the
> machine being pinged. Does anyone know of any ping apps that will do
> such a thing? I am trying to do this to do some latency testing, of course
> I have the time that the ping was sent from the pinging side and the time it
> came back (if it did) but I would also like to log the time the ping was received
> and echoed back on the pinged end.
One way of doing it is to use ipchains/iptables to log (but not drop)
packets, but this will only tell you a packet got there at this time,
not that a specific packet arrived.
Unless you like hacking kernels, pinging is not the answer. I'd setup
some sort of UDP client/server with the payload being some encoded time
so you know when the packet is sent. You could even stamp the replies
with the remote ends clock.
Getting the clocks right is critical with that sort of thing for obvious
reasons.
I'd also look at NTP. A side-effect of what it does is it works out the
delay between hosts. It does lots of funky stuff to do it.
Of course you can always cheat and use RTT/2 but that assumes symmetric
delays.
- Craig
-- Craig Small VK2XLZ GnuPG:1C1B D893 1418 2AF4 45EE 95CB C76C E5AC 12CA DFA5 Eye-Net Consulting http://www.eye-net.com.au/ <terhi.victor@logonet.com> MIEEE <ywtnqxu@ispwest.com> Debian developer <nrybeiab.ljaxah@ertel.com.pl> - To unsubscribe from this list: send the line "unsubscribe linux-hams" in the body of a message to tmsjjykb.tptisz@datapath.co.uk
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