[openib-general] RDMA connection and address translation API

[Caitlin Bestler]

I think it would be more accurate to state that DAPL requires the 128-bit
"IA Address space" to be administratively subdivided so that each "subnet"
unambiguously translates to a specific IA reached network and that
translation
of the "IA Address" into and from that network's wire protocol is not visible
to the DAT Consumer.

ATS is indeed *one* solution for doing so. Adding RARP to IPoIB would make
for another solution. Direct translation is also a valid solution for IPv6
compatible network IDs.

So with this wealth of options available, do you agree that there is no
reason to elevate any of these issues to being visisble to a transport
neutral application? 

-----Original Message-----
From: openib-general-bounces at openib.org
[mailto:openib-general-bounces at openib.org] On Behalf Of Roland Dreier
Sent: Wednesday, August 24, 2005 2:31 PM
To: James Lentini
Cc: openib-general at openib.org
Subject: Re: [openib-general] RDMA connection and address translation API

    Roland> No, I think we just need to realize that a perfectly
    Roland> transport neutral protocol implementation is not
    Roland> achievable.  It's unfortunate that kDAPL fooled people by
    Roland> hiding the details of the wire protocol under a supposedly
    Roland> "neutral API," but the fact is that mapping an abstract
    Roland> RDMA transport to a real implementation will always
    Roland> involve arbitrary transport-dependent choices.

Further: if we would be willing to say that transport-neutral protocols must
use a "kDAPL wire protocol," then there's no problem in defining that wire
protocol to put the source and destination IP address somewhere in the CM
private data.  The current "kDAPL wire protocol" happens to use ATS to try
and achieve this (although it doesn't handle the multi-homed case), but that
is no more and no less of an arbitrary protocol design choice.

So in a nutshell, my objection to using ATS is that it is an arbitrary design
choice that doesn't work as well as other equally valid choices.

 - R.
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