Re: initiator depth and responder resources in a connect request.

[Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

On 03/14/2011 05:12 PM, Hefty, Sean wrote:
>> When you say 'client must then determine', do you mean the client
>> application?  So the IB CM really just passes along
>> these values and doesn't really enforce any semantics?
> Yes and yes.  (The ib cm is probably a bit brain dead on this, but the librdmacm does check for this error.)  From the IB spec (sections intentionally reversed) see the two areas marked *****:
>
> 12.7.30 INITIATOR DEPTH
> The maximum number of outstanding RDMA Read/Atomic operations the
> sender will have to the remote QP/EEC. This value may be zero. The
> maximum number that the HCA can support for a QP/EEC can be determined
> using the Query HCA verb. See section 11.2.1.2 Query HCA.
> InfiniBandTM Architecture Release 1.2.1 Communication Management November 2007
>
> *****The recipient of the REQ message should try to choose a number of local
> Responder Resources that is greater than or equal to the Initiator Depth
> in the REQ message. If it is unwilling or unable to do so, it may send a
> REP message containing fewer Responder Resources than the Initiator
> Depth in the REQ message.*****
>
> 12.7.29 RESPONDER RESOURCES
> The maximum number of outstanding RDMA Read/Atomic operations the
> sender will support from the remote QP/EEC. This value may be zero. The
> maximum number that the HCA can support for a QP/EEC can be determined
> using the Query HCA verb. See section 11.2.1.2 Query HCA.
>
> The recipient of the REQ message shall choose a local Initiator Depth that
> does not exceed the Responder Resources offered in the REQ. If the recipient
> of the REQ message is unwilling or unable to do so, it shall send a
> REJ message to discontinue the connection establishment.
>
> *****The recipient of the REP message shall decide whether the Responder
> Resources offered in the REP are sufficient for the Initiator Depth the recipient
> of the REP wishes to use.***** If not, it shall send a REJ message to
> discontinue the connection establishment.
>
>
>> The reason I'm asking is we're reviewing the IETF ID that extends MPA
>> connection setup to allow negotiating ORD/IRD.
>> And I think we should not diverge from the way its done in IB.  IE: the
>> RDMACM semantics should be the same IMO.
> What does iwarp do now?

The current IETF specs leave it up to the applications/ULPs to deal with it.  Neither ORD or IRD are exchanged as part 
of MPA or other iWARP protocol negotiations.
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