Wireshark · Ethereal-users: Re: [Ethereal-users] Network Traversal Time

["Ronnie Sahlberg" <ronnie_sahlberg@xxxxxxxxxxxxxx>]

----- Original Message ----- 
From: "Ian Schorr"
Sent: Thursday, March 11, 2004 5:26 AM
Subject: Re: [Ethereal-users] Network Traversal Time


> Especially in field service circumstances or others where using "fixed"
> network probes is difficult, network connectivity for a recording
> device is spotty/unavailable, etc, it can be difficult to ensure that
> clocks are very very tightly synchronized.

I think there are USB based GPS time receivers that can be used in the
field.
Use it on all the capture devices one by one to set the time reasonably
accurately before initiating the capture.

For extremely low latency networks this might not be possible anyway since
there is additional latency added in the order
of  ms in some GbE and faster NICs anyway that will poison the timestamp
accuracy. (to collapse multiple packets into a single interrupt and thus
reduce cpu load and number of interrupts)


Maybe some sort of usb gps time receiver (all hosts today come with usb
ports?) with a cdrom (all hosts today can read cdroms)
containing drivers for all popular OS's (linux, bsd, win32, solaris, aix,
hpux(no we dont want to take captures using nettl. period. strike that one))
might be sufficient for most uses?

Once set, the local oscillator will not drift that quickly...