Re: GSoC 2011 project proposal [packet timestamping]

[David Young <dyoung%pobox.com@localhost>]

On Mon, Mar 28, 2011 at 06:56:58PM +0200, Hubert Feyrer wrote:
> 
> Am 28.03.2011 um Mo. 28.03.2011 17:52 schrieb Dmitry Cherkassov:
> > Right now NetBSD provides some basic packet timestamping which
> > needs to be extended and implemented in NIC drivers.
> 
> This is probably a stupid question, but: 
> why in the NIC drivers, and not in the MI UDP/IP code?

There are NICs that supply stamp received packets with the rx time at
microsecond (or higher) resolution.  For example, some WLAN NICs supply
microsecond rx times from the network clock that sychronizes 802.11
beacon transmission and power-saving sleep/wake.  It seems that the
Intel 82599 10-gigabit ethernet can capture both packet tx and rx times,
and at higher than microsecond resolution.

Sometimes the NIC documentation or relevant standards describe precisely
when/where in the rx/tx chain the rx/tx time is latched, which helps for
using the timestamps for scientific/esoteric purposes.

Dave

-- 
David Young             OJC Technologies
dyoung%ojctech.com@localhost      Urbana, IL * (217) 344-0444 x24