Re: Half Duplex and Zero Copy IP

[Andi Kleen]

In article <[e-mail]>,
[e-mail] (Subba Rao) writes:
> Hello,
> I have 2 3Com NICs on my system. They are 3c905C Tornado PCI cards.
> The drivers are compiled into the kernel (Slackware 8.0 with kernel 2.4.7).

> One of the interfaces will be used as a sniffer interface (without IP address)
> and a very high traffic pipes. I do not wish to loose any packets coming to this
> interface. Is it better if I initialize the interface in HALF DUPLEX mode? If yes,
> how do I set the card to HALF DUPLEX mode? How can I find out the HW (NIC) settings
> on the system?

Half duplex mode will only make your line slower, it has no benefit.

> Another question about 3Com NICs, do they perform zero-copy IP? I read that
> the performance improves a lot WITHOUT zero-copy IP.

The sniffer zero copy implementation as implemented in some libpcaps 
does not depend on any special NIC support; it should work with any.

-Andi