[ofa-general] [RFP] support for iWARP requirement - active connect side MUST send first FPDU

[Michael Krause]

At 01:17 PM 10/23/2007, Steve Wise wrote:


>Sean Hefty wrote:
>>>There has been much discussion on a private thread regarding bug #735 - 
>>>"dapltest performance tests don't adhere to iWARP standard" that needs 
>>>to move to the general list.
>>This bug would be better titled "iWarp cannot support uDAPL API". :)
>>Seriously, the iWarp and uDAPL specs conflict.  One needs to change.
>>
>>>Can someone come up with a solution, possibly in iWARP CM, that will 
>>>work and insure interoperability between iWARP devices?
>>I thought the restriction was there to support switching between 
>>streaming and rdma mode.  If a connection only uses rdma mode, is the 
>>restriction really needed at all?
>
>Yes because all iWARP connections start out as TCP streaming mode 
>connections, and the MPA startup messages are sent in streaming mode. Then 
>the connection is  transitioned into FPDU (Framed PDU) mode using the MPA 
>protocol.

Correct.  The IETF was very clear on these requirements (significant debate 
occurred over at least 12-18 months) and there is unlikely to be any 
traction in changing the iWARP specifications to provide another 
mechanism.  Best to provide API that detect which semantics are required 
and then if the application cannot adjust, then it cannot use the iWARP 
semantics.

BTW, if one uses the SDP port mapper protocol (see the IETF SDP 
specification), one can detect from the start that RDMA is being used and 
one could start in RDMA mode sans the MPA requirement.   The SDP port 
mapper protocol also enables one to apply various other policies such as 
determining whether the application / remote node session should be allowed 
to run over RDMA or not - simple point of control for management.

Mike 
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