Subject: RE: [Ipoverib] please read: Clarification on GUID's universal/loc al bit

From: Diego Crupnicoff <[email-masked]>
Date: Mon, 24 May 2004 05:14:53 -0700

Hi Margaret,

> (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.

I think it may actually be safe to assume that the IB GUID in question is
__always__ globally unique (regardless of the value in its "u" bit). The IB
spec says: 

"The manufacturer assigns an EUI-64 __with_global_scope_set__"

The IPv6 IID can therefore be based on this manufacturer assigned GUID which
is __required__ by the IB spec to be one with global scope. The mechanism
for building the IPv6 IID could then be as simple as taking the IB mfg
assigned GUID and set (if it was not already so) its "u" bit (i.e. ignore
the interpretation that the vendor may have given to the IB spec).

To close the loop, the IBTA would have to explicitly forbid the use of the
same 63 bit combination with two different values for the u bit as two valid
globally unique GUIDs. I can't speak for the entire IBTA but it looks to me
that this would be acceptable. Furthermore, it is my understanding that the
definition of locally unique IB GUIDs would then be irrelevant to the ipoib
spec.

Does it make sense?

Thanks,

Diego

---

From: Daniel Cassiday <[email-masked]>
Date: Mon, 24 May 2004 17:28:02 -0400

The IBTA link WG (who is responsible for this mess in the first place) 
has discussed this issus and is exploring solutions.

The current thinking is not to use the u bit to indicate global scope. 
Instead, any locally administered IB addresses (i.e. IB 64-bit Global 
identifiers) would use a reserved vendor identifier (i.e. a reserved 
OUI).  Any IB 64-bit Global ID that does not use this vendor tag will 
have global scope and be globally unique.

In this approach, the IBTA would apply to the IEEE Registration 
Authority for a OUI to be used for this purpose. The IBTA would also 
clarify the IBA spec and add the requirement the "u" bit is ignored in 
the EUI-64 (i.e. a vendor cannot have two EUI-64s differing only in the 
value of the "u" bit)

Diego Crupnicoff wrote:
> I think it may actually be safe to assume that the IB GUID in question 
> is __always__ globally unique (regardless of the value in its "u" bit). 
> The IB spec says:
> 
> The IPv6 IID can therefore be based on this manufacturer assigned GUID 
> which is __required__ by the IB spec to be one with global scope. The 
> mechanism for building the IPv6 IID could then be as simple as taking 
> the IB mfg assigned GUID and set (if it was not already so) its "u" bit 
> (i.e. ignore the interpretation that the vendor may have given to the IB 
> spec).
> 
> To close the loop, the IBTA would have to explicitly forbid the use of 
> the same 63 bit combination with two different values for the u bit as 
> two valid globally unique GUIDs. I can't speak for the entire IBTA but 
> it looks to me that this would be acceptable. Furthermore, it is my 
> understanding that the definition of locally unique IB GUIDs would then 
> be irrelevant to the ipoib spec.
> 
> Does it make sense?
> 
> Thanks,
> 
> Diego
> 

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---

From: Margaret Wasserman <[email-masked]>
Date: Tue, 25 May 2004 20:40:15 -0400

Hi Daniel,

It is good to know that the IBTA is working to address this issue.

If I understand your proposal correctly, once this change has been 
adopted by the IBTA, the correct way to build a IPv6 IID from a GUID 
would be:

(1) Start with the 64-bit GUID
(2) If the OUI portion of the GUID is equal to the specified value, 
then the "u" bit should be cleared (regardless of its original value) 
to indicate that the IID is locally administered.
(3) Else (if the OUI portion of the GUID does not equal the specified 
value) the "u" bit should be set
(regardless of its original value) to indicate that the IID is globally unique.

If I am understanding you correctly, this would always result in the 
proper setting of the "u" bit in IPv6 addresses.

What is the timeframe for an IBTA decision on this issue?  This is 
somewhat urgent, as we won't be able to finalize and approve the 
IPOIB specification until this issue is resolved in the IBTA.

Thanks,
Margaret

At 5:28 PM -0400 5/24/04, Daniel Cassiday wrote:
>The IBTA link WG (who is responsible for this mess in the first 
>place) has discussed this issus and is exploring solutions.
>
>The current thinking is not to use the u bit to indicate global 
>scope. Instead, any locally administered IB addresses (i.e. IB 
>64-bit Global identifiers) would use a reserved vendor identifier 
>(i.e. a reserved OUI).  Any IB 64-bit Global ID that does not use 
>this vendor tag will have global scope and be globally unique.
>
>clarify the IBA spec and add the requirement the "u" bit is ignored 
>in the EUI-64 (i.e. a vendor cannot have two EUI-64s differing only 
>in the value of the "u" bit)
>