Phrased that way, I do not think any stack anywhere looks at the U or G
its in a received IPv6 address.
I have no problem if we declare hem to be irrelevant.
Your,
Joel
On 12/18/2012 8:13 PM, Fred Baker (fred) wrote:
As you know, the EUI-64 address is but one of the seeds that an EID can be
generated from. Having been generated, it's a bit string, and another bit
string either equals it or doesn't.
You didn't answer my question.
What, on an IPv6 host or router, cares about the g bit apart from the code that
uses an EUI-48 or EUI-64 to create an EID? What starts from an EID and extracts
from it an EUI-64/48 address, or in any other way interprets the g flag in an
EID?
u and g are a recurring theme. Apart from the people who wrote RFC 4291, who
are under the delusion that the only link layer in the world is an Ethernet,
who actually cares?
On Dec 18, 2012, at 5:06 PM, Joel M. Halpern wrote:
As I understand it, the original intent with the U bit was to provide an easy
way to create IID that were highly likely to be distinct from all other IIDs
(on the link). As IEEE reserves the G bit, we marked that as special as well
when the U bit was set.
Changing the meaning of U=1, G=0 seems a major chane with no particular benefit.
When we defined it, we were unclear about the U=1, G=1 case. Given the way the
U bit is defined, U=1, G=1 can not occur in the normal course of events. We
can ignore it. we can define it. We can reserve it and thn sit on our hands.
But given taht we have text already, and that text is ambiguous, it seems like
we should at least clear up the ambiguity.
Yours,
Joel
On 12/18/2012 7:35 PM, Fred Baker (fred) wrote:
Why do we care about u and g in the first place? Is there code in an IPv6
router or host that interprets them?
On Dec 18, 2012, at 3:50 PM, Joel M. Halpern wrote:
In reading the discussion,a nd trying to think through what I understand to be
correct, it seems that there is an unforeseen ambiguity in the way the current
documents about IPv6 IIDs are written.
I think that there are two possible meanings, ad we should decide explicitly
which one we want.
1) u=1 means that the IID is derived from an IEEE OUI (of some form). With that
meaning, u=1, g=1 is clearly some sort of multi-entity identifier. And we
should say that somewhere.
2) u=1, g=1 was unforeseen, and we don't know what it means. In that case, we
ought to figure out how we want that portion of the IID space used, and write
it down clearly. It seems to me that allowing this space to be used for
special-semantic IIDs (with suitable care so that the entire ecosystem is not
affected by them) is a very reasonable path.
It seems unlikely that there is actual practice in the wild with u=1, g=1 under
either interpretation. We do now have a request to start using it (4rd). So
we should decide.
Yours,
Joel
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