[swg] RE: [openib-general] socket based connectionmodel for IB proposal -round 4

[Sean Hefty]

Kanevsky, Arkady wrote:
> Sean,
> SWG discussed today the extending private data format proposal to
> SIDR_REQ.
> The group does not see the need for it since ULP is no RDMA aware.
> That is ULP does not use RDMA operations.
> Do you have some specific ULP in mind for this functionality?
> For UDP a different IP address can be used for each message. There is no
> persistent connection.

I didn't have any particular ULP in mind.  I was thinking more of a generic 
application that wanted to use UDP style addressing over IB, similar to what's 
being discussed for using TCP style addressing over IB.

It seems that there needs to be a way to map a given destination address to a 
remote QP/qkey.  Regardless if the IP address is carried in each ULP message, it 
would still need to be in the SIDR REQ in order to locate the correct QP.

Such a ULP won't use RDMA or atomic operations, but still benefits by having QP 
and CQ semantics, such as direct hardware access from userspace and pre-posted 
receive buffers, while avoiding the overhead of IP (or IPoIB).  So, I would 
consider the application as being "RDMA aware", with "RDMA" hardware defined as 
that which provides QP semantics.  I view it similar to applications that sit 
over DAPL that do only sends and receives.

In any case, this can be treated as a separate issue than what's being defined 
for connections.  It could just be beneficial that if it is ever defined that it 
use the same private data format.

- Sean