Subject: RE: [rddp] Some Minimal end-to-end Buffer Rules Required

From: "Culley, Paul" <[email-masked]>
Date: Thu, 17 Jul 2003 04:23:08 -0500

> -----Original Message-----
> From: Caitlin Bestler [mailto:[email-masked]] 
> Sent: Wednesday, July 16, 2003 9:10 AM
> To: John Hufferd
> Cc: [email-masked]
> Subject: Re: [rddp] Some Minimal end-to-end Buffer Rules Required
> 
> 
Deleted...
> 
> Then these applications do not work over InfiniBand? You have
> a credit limit over IB RC, and it is even less flexible than 
> what you can do with iWARP.
> 
Actually these applications (that occasionally send more messages than
normally credited) could work quite well on IB because IB supports
automatic flow control for the RC mode receive queue buffers.  In the
"normal" case, the flow control is not invoked, everything flows
smoothly.  In the exceptional case when too many messages need to be
sent, IB backs up the messages at the sender (in the Send Queue).

Paul C.

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From: Caitlin Bestler <[email-masked]>
Date: Thu, 17 Jul 2003 08:51:03 -0500

>sent, IB backs up the messages at the sender (in the Send Queue).

Correct. But that service is not provided by the RDMA layer with
iWARP because it would require an iWARP layer ack message.

A minimal adaptation would be for the application to queue them
itself, and release them in response to ULP acks (associated with
untagged messages).

I am assuming that there is still agreement that while transport
layer queuing is a nice feature, it does not justify additional
wire traffic. Agreed?