[openib-general] [ANNOUNCE] ContributeRDS(ReliableDatagramSockets) to OpenIB

[Fab Tillier]

> From: Bob Woodruff [mailto:robert.j.woodruff at intel.com]
> Sent: Friday, November 04, 2005 10:58 AM
> 
> Fab wrote,
> >There is not a 1:1 relationship between a UDP application socket
> >and an IB QP, rather there is a single IB connection between systems
> >over which traffic from multiple UDP sockets flows.
> 
> That would probably provide better scalability, since there
> would not be a 1:1 mapping between UDP sockets and IB connections,
> however for large clusters there may still be a scalability issue
> if every node needs to have a connection to every other node.
> If you implemented it on top of datagrams instead, then each node
> would only need one QP, rather than one for every node in the cluster.

Doing a UDP to IB-UD protocol is unlikely to buy you anything over just using
IPoIB.  I don't know about doing UDP to IB-RDD, but the complexity of supporting
end to end contexts and RDD QPs seems to me to outweigh the complexity of doing
SW multiplexing over multiple IB-RC QPs.  I don't think software multiplexing
over IB-RC costs much from both a system/HCA resource and performance
perspective, especially compared to doing something like uDAPL or SDP where
there's a 1:1 relationship between EP or socket to QP, respectively.

- Fab