Re: Hardware timestamp ?

[Pierre Karampournis <pkarampournis () gmail com>]

Guy Harris wrote :
> On Feb 27, 2009, at 9:03 AM, Pierre KARAMPOURNIS wrote:
>
> > I worked on old Linux Kernel versions so I will try the latest ones 
> > to see
> > hardware timestamping. So now I have to search for Network cards 
> > which can
> > timestamp the packets with nanosecond resolution (Endace DAG cards can
> > apparently do that)
>
> Yes, but they're not regular networking cards, so they won't use that 
> kernel code path on Linux; they supply packets through their own API, 
> and that API does provide nanosecond timestamps, which libpcap turns 
> into microsecond timestamps.
>
> If you want a network card that supplies its own timestamps *and* 
> functions as a regular network adapter rather than a capture-only 
> adapter, it would need to have a Linux driver that time-stamped the 
> skbuff containing the packet.  I don't know whether any cards of that 
> sort exist, or whether they have Linux drivers that do that (if they 
> have open-source Linux drivers that don't, you could perhaps modify 
> them to do so).
>
> If, as you said, you're planning to capture traffic on a 
> gigabit-or-faster network, you might *want* a capture-only NIC for 
> that purpose, in which case the Endace cards would be sufficient.
I only need to capture data so endace cards should do the job. I will 
also modify libpcap to keep the original timestamps with nanosecond 
resolution so I consider the problem "solved".
I didn't know the Endace devices, I was not searching in that direction, 
thank you for your help.

Pierre
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