[openib-general] RFC: detecting duplicate MAD requests

[Hal Rosenstock]

On Mon, 2006-05-01 at 14:04, Sean Hefty wrote:
> >> There is a real issue that is seen when a duplicate request (same TID, SGID,
> >> mgmt class) is received at the client, resulting in a duplicate response.
> >
> >You had mentioned in the previous email on this that this was the case
> >of a slow responder. Is the responder slow but playing by the IB
> >timeouts in effect or is it violating those timeouts ?
> 
> I don't believe that the responder is violating any timeouts.

Why is the requester resending ?

> >> The MAD layer cannot allow the duplicate response to be sent because of RMPP
> >issues.
> >
> >Is this different for non RMPP MADs v. RMPP MADs ? Is the RMPP issue
> >what you mention below (RMPP receiving a duplicate response) ? If so, is
> >this an implementation or architecture issue or both ?
> 
> The issue is a result of the RMPP architecture, but I wouldn't say that RMPP has
> an issue.  It's simply a matter that you can't reassemble multiple MADs from the
> same source that use the same transaction ID.
> 
> For non-RMPP MADs, the only issue is one of efficiency.  A duplicate response
> would just be dropped on the requester side if the first response is received.
> 
> >> A client is still restricted from sending a duplicate response while a
> >previous
> >> response is in progress.  RMPP cannot handle this case.
> >
> >Why not ? Wouldn't the second response not match anything in the client
> >on the request side ?
> 
> This is true if the first response completes before the second response is sent.
> The problem is when both responses are active at the same time.
> 
> - Sean