[swg] Re: [openib-general] TCP/IP connection service over IB

[Ted H. Kim]

Tom,

Some comments inline ...


Tom Tucker wrote:
> I think it's relevant, so let's make sure my assumptions are correct:
> 
> - The ITAPI will be a "ULP" on OpenIB

ITAPI is like uDAPL, so if uDAPL is a "ULP" then the answer is yes.
The point is that for uDAPL you have the actual "app" running over
uDAPL. So I guess it's a matter of terminology whether uDAPL is
a ULP or is it some sort of middleware with the app being the "ULP".


> - The ITAPI will create the IRD/ORD headers in its private data and
> submit this as part of its connection establishment. 
> - The ITAPI consumer at the remote peer will use this data to configure
> it's local QP before accepting the connection
> 
> Over IB, the IRD/ORD private data will be prepended with a "private data
> header" that contains the source and destination IP addresses, source
> port, etc... The remote peer will not see this data as part of the
> private data, but rather will see it in the CMA event in the upcall.

Over IB, the IRD/ORD data is already built in to the standard CM
stuff (i.e. the "responder resources" and "initiator depth" fields of
REQ and REP). So no additional demands are made on private data for IB
in ITAPI for the IOH purpose. Of course the ITAPI app (like a uDAPL app)
can also use private data for app specific/ULP reasons.


> Over iWARP/MPA, there will be nothing else in the private data except
> what was provided by the consumer (ITAPI in this case). The reason being
> that this extra information (IP addressing info) is in the protocol
> header proper.

Just to restate for clarity, ITAPI for iWARP will use the first 16 bytes of
MPA private date for the IOH (IRD/ORD header). The rest is usable for
app/ULP reasons.


I should point out that there was once a proposal of doing a RDDP IETF
draft which would have sub-divided the MPA private data into a
"middleware" section and an "app" section. The idea was to be sure that
the app/ULP and middleware (e.g. the IOH) uses of private data would not
step on each other. I think this idea did not progress, mostly because
the author (John Carrier, formerly of Adaptec) changed jobs and was no
longer working on iWARP stuff.

While not directly proposed, this idea could have been carried over to IB.
Some of the ideas on this thread are already implicitly
doing this middleware (for IP addressing purpose) vs ULP/app split.


-ted