RE: please read: Clarification on GUID's universal/loc al bit
Margaret Wasserman <margaret <at> thingmagic.com>
2004-05-24 02:51:36 GMT
At 5:56 PM -0700 5/23/04, Diego Crupnicoff wrote:
We know of deployed IB implementations where the "u" bit in the GUID
The IBTA LWG has discussed this matter but no formal resolution has
yet been voted. The LWG is looking for a way to solve the problem
without affecting any existing implementation.
Given the above, I would suggest that IPoIB should define the way to
derive an IPv6 interface identifier from an IB-port-GUID without
making any assumptions on the value of its "u" bit.
Given the apparent ambiguity in the IB specification, there are only
two things that I can think of to do in this situation:
(1) Ask the IBTA to clarify their specification, with the hope that
vendors will update their implementations to match the clarified
value. It seems unlikely, though, that this is a practical choice if
vendors have already shipped hardware that has burned-in values with
different interpretations of the "u" bit.
(2) Accept that we cannot tell, by looking at an IB GUID, whether it
is of global or local scope. In this case, the conservative choice
would be to treat all IB GUIDs as if they are of local scope, always
clearing the "u" bit in the IPv6 IID, regardless of how the bit is
set in the IB GUID.
There is a potential downside to choice (2): If we do come up with
mechanisms that can take advantage of the fact that some IIDs are
globally unique (to simplify routing, host identification, etc.),
those mechanisms would not work on IB nodes. However, I can't think
of any other practical choice.
What do others think we should do here?