How to generate PAUSE frame

[Jeff Haran]

> -----Original Message-----
> From: kernelnewbies-bounces at kernelnewbies.org [mailto:kernelnewbies-
> bounces at kernelnewbies.org] On Behalf Of bill
> Sent: Wednesday, July 20, 2011 11:11 PM
> To: kernelnewbies
> Subject: How to generate PAUSE frame
> 
> Hi, all
> 
> 
> I have a 10G NIC card with fiber interface, this NIC is drived by a
private os
> with l2 rxonly forwarding function,
> and I want to test this NIC could sent out PAUSE frame.
> 
>   host                       client
> +--------+                +------------+
> |            |    fiber       |  10G NIC |
> |  NIC    |  <===>   |  l2fwd      |
> |            |                 |  rxonly     |
> +--------+                +------------+
> 
> If host send packet faster than client could receive, client 10G NIC
should
> send out PAUSE frame,
> and use "ethtool -a eth0" on host to show any PAUSE frame received.
> 
> How could I do this without any faster NIC card than 10G?
> 
> 
> 
> thanks
> 
> bill

I think you are going to have a hard time finding any host in the form
of a general purpose computer that can saturate a 10G link.

You probably want to look into commercial frame generators from
companies like Smartbits or Ixia. They have special hardware for doing
this kind of thing. These solutions aren't cheap though.

You *MIGHT* be able to do this if you replaced host with the right 10G
switch. I am thinking if you turned off spanning tree and then looped a
fiber from one of the switch ports back to another one, and then caused
a broadcast frame (say an ARP request) to be injected into a third
switch port, you might be able to cause a broadcast storm which would
hit client's interface and that might be a high enough packet rate to
make it generate a pause. The question then would be if the switch has
the right software to report whether it received a pause from client.
And I really don't know if this solution would be cheaper than getting
one of the frame generators.

Jeff Haran