[openib-general] mapping between IP address and device name

[Michael Krause]

At 10:30 AM 6/24/2005, Roland Dreier wrote:
>     Thomas> As I said - I am not attached to ATS. I would welcome an
>     Thomas> alternative.
>
>Sure, understood.  I'm suggesting a slight tweak to the IB wire
>protocol.  I don't think there's a difference in the security
>provided, and carrying the peer address in the CM private data avoids
>a lot of the conceptual and implementation difficulties of ATS.
>
>     Thomas> But in the absence of one, I like what we have. Also, I do
>     Thomas> not want to saddle the NFS/RDMA transport with carrying an
>     Thomas> IP address purely for the benefit of a missing transport
>     Thomas> facility. After all NFS/RDMA works on iWARP too.
>
>I'm not sure I understand this objection.  We wouldn't be saddling the
>transport with anything -- simply specifying in the binding of
>NFS/RDMA to IB that certain information is carried in the private data
>fields of the CM messages used to establish a connection.  Clearly
>iWARP would use its own mechanism for providing the peer address.
>
>This would be exactly analogous to the situation for SDP -- obviously
>SDP running on iWARP does not use the IB CM to exchange IP address
>information in the same way the SDP over IB does.

Actually, SDP on iWARP uses the SDP port mapper protocol to comprehend the 
IP address / port tuples used on both sides of the communication before the 
connection is established (this protocol could be used by any mapping 
service since it is implemented on top of UDP so could be re-used by other 
subsystems like NFS.  The TCP transport then connects normally and one can 
ask it for the IP address / port tuple that is really being used.   Port 
mapper may be viewed as akin to the SID protocol defined for IB.  The SDP 
hello is then exchange in byte stream as opposed to IB CM.

The port mapper supports both centrally managed and distributed usage 
models, supports the ability to return diff IP address than requested, 
support multiple IP addresses per port, etc.  One can construct a very 
flexible infrastructure that supports nearly any type of mapping one 
desires to same or different hardware or endnodes.  It is fairly light 
weight and can support caching of data for a period of time or even a 
one-shot connection attempt.

Mike  
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