[openib-general] RMPP and timeouts/retries

[Eitan Zahavi]

Hi Sean,

This seems very nice. Thank you.
The only thing I dislike in this API is the "implicit" behavior. I would
prefer a clear flag saying - is_response_expected. Rather than the timeout
to flag this. But this is a matter of taste not functionality. 

Eitan Zahavi

> -----Original Message-----
> From: Sean Hefty [mailto:sean.hefty at intel.com]
> Sent: Wednesday, June 08, 2005 8:05 AM
> To: 'Hal Rosenstock'; Sean Hefty
> Cc: openib-general at openib.org
> Subject: RE: [openib-general] RMPP and timeouts/retries
> 
> >> I'm having some trouble using timeouts and retries with RMPP. The issue
> >> I see is that what constitutes a response is different than normal MADs
> >> for RMPP. With the current "definition" of response, is the
> >> timeout/retry only usable on the SA client side where the normal
> >> definition is more closely followed ? If so, is there still an issue
> >> with SA GetTable as the initial request is not RMPP ?
> 
> The SA client should set the timeout > 0 to indicate that a response MAD
is
> expected.  It can set retries, but isn't required to do so.
> 
> >Is the response not at the RMPP level ? So a response would be for dual
> >ended RMPP ?
> 
> Request/response is separate from RMPP.  Request/response is defined at
the
> message level from the viewpoint of the user of the MAD layer.  (I.e. is
the
> response bit set in the MAD header, regardless of the size of the MAD.)
> 
> Setting timeout > 0 when sending indicates that a MAD should be received
with
> the response bit set that is in reply to the request.  If timeout = 0 but
RMPP
> is marked active, the MAD will still invoke RMPP and not complete until
all
> segments have been ACKed.  (I.e. the completion of an RMPP send indicates
that
> the MAD was received.)
> 
> Retries is a little more complex.  It indicates the number of times to
send a
> request in hopes of receiving a response (if one is expected) or an ACK
(if
> using RMPP).
> 
> >> On the SA side, there does not appear to be a way to use this feature.
> >> Is that correct ?
> 
> For the SA side responding to a request, you would want to set retries >
1, but
> timeout = 0.  Timeout of 0 indicates that no response is expected, since
the SA
> is sending the response.  Having a retry count would allow a
retransmission if
> an ACK were lost.
> 
> You should be able to mix RMPP and non-RMPP MADs without restriction: non-
> RMPP
> request - RMPP response, RMPP request - non-RMPP response, RMPP request
and
> response, non-RMPP request and response.  If one of these conditions
doesn't
> work, then there's a bug in the code.  I'm pretty sure that I tested all
of
> these combinations, but that doesn't mean that it won't hit a bug talking
with
> another RMPP implementation.
> 
> - Sean
> 
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