[openib-general] [PATCHv4] IPoIB CM Experimental support

[Bernard King-Smith]

----- Message from "Roland Dreier" <rdreier at cisco.com> on Wed, 10 
> Jan 2007 07:15:12 -0800 -----
> 
> To:
> 
> "Michael S. Tsirkin" <mst at mellanox.co.il>
> 
> cc:
> 
> openib-general at openib.org
> 
> Subject:
> 
> Re: [openib-general] [PATCHv4] IPoIB CM Experimental support
> 
>  > - Using path MTU discovery, multicast and UDP traffic to UD mode now 
work,
>  >   only a small number of packets is dropped.
> 
> How does this work?  What happens if I set my MTU to 8K and send a
> 8000-byte UDP message to a node that doesn't implement CM?  What
> happens if I send an 8000-byte UDP multicast?

If we support a large interface MTU using RC, then I would expect both UDP 
and TCP to both use RC mode. It doesn't make sense for UDP to use UD mode 
because of the higher CPU overhead and lower bandwdith, when TCP uses RC. 
Can we not support UDP multicast over RC?

> 
> I didn't think UDP did path MTU discovery by default...
> 
>  - R.
> 
> 
> 


Bernie King-Smith 
IBM Corporation
Server Group
Cluster System Performance 
wombat2 at us.ibm.com    (845)433-8483
Tie. 293-8483 or wombat2 on NOTES 

"We are not responsible for the world we are born into, only for the world 
we leave when we die.
So we have to accept what has gone before us and work to change the only 
thing we can,
-- The Future." William Shatner
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openfabrics.org/pipermail/general/attachments/20070110/6b0eb07d/attachment.html>