ORBIT-USER: Questions about MAC cards ...

[Brian K. Russell]

On Sat, 02 Dec 2006 18:04:14 -0500
 Mesut Ali Ergin <ergin at eden.rutgers.edu> wrote:
> Assuming you are referring to wired/wireless NICs,

Yes, that is true.

> 
> 1. They do have multiple frame holding buffers. (e.g. ORBIT Atheros
> 5212 cards have a 50-frame buffer)
> 
> 2. They behave exactly the way an interrupt driven device should 
> behave. You can give it as many as 50 packets as fast as you can, it 
> will let you know what happened to those packets (individually or in
> bunches) by generating interrupts and calling registered ISR of the 
> driver.

This explains a great deal.  If I generate packets at some fixed rate
and send them to the buffered MAC card, they may not get transmitted at
the same rate.  In fact, under conditions of contention, I may end up
buffering all 50 packets and then having them go out in rapid
succession.  That would explain the burstiness I've seen quite nicely.

Thank you.

BKR
> 
> --
> MAE
> 
> 
> Brian K. Russell wrote:
> > 1. Do MAC cards have buffers for multiple outgoing packets or is
> there
> > room for just one packet at a time?
> > 
> > 2. If a MAC card is busy with an outgoing packet (unicast or
> broadcast),
> > what happens if another outgoing packet is given to the MAC card
> before
> > it's finished with the its current outgoing packet?
> > 
> > Thank you.
> > 
> > BKR
> >