Robert,

I believe we are just going to disagree on the issue you have.

You seem to be saying that the addr arch document (in order to go to
Draft) requires that there exist at least 2 implementations that
enforce the requirement that IIDs are exactly 64 bits. That is, they
MUST NOT allow IIDs of length other than 64 to be used/configured.

The actual requirement that IIDs be 64 bits is not an implementation
requirement (in the addressing architecture document). It is a
principle that is to be followed by other documents that specify usage
of the IID. The last part of Section 2.5.1 says:

   The details of forming interface identifiers are defined in the
   appropriate "IPv6 over <link>" specification such as "IPv6 over
   Ethernet" [ETHER], "IPv6 over FDDI" [FDDI], etc.

All the other IPv6 over foo documents are consistent with addr arch in
this regard.

I also remain unconvinced that the wording:

   For all unicast addresses, except those that start with binary value
   000, Interface IDs are required to be 64 bits long and to be
   constructed in Modified EUI-64 format.

translates into a requirement that there exist implementations that
disallow IIDs of length other than 64. Following this logic, I suspect
one could effectively prevent just about any document from being
advanced to Draft. Documents typically have a number of principles
that are not testable or enforceable, or where no one would bother to
actually enforce something because the actual cost is too
high. Consider:

>     2.5.5 IPv6 Addresses with Embedded IPv4 Addresses
> [...]
>    |                80 bits               | 16 |      32 bits        |
>    +--------------------------------------+--------------------------+
>    |0000..............................0000|0000|    IPv4 address     |
>    +--------------------------------------+----+---------------------+
>    Note: The IPv4 address used in the "IPv4-compatible IPv6 address"
>    must be a globally-unique IPv4 unicast address.

What implementations prevent a non-globally unique IPv4 address from
being used here?  By your logic, this requirement would need to be
stricken from the document.

Or:

>    All interfaces are required to have at least one link-local unicast
>    address (see section 2.8 for additional required addresses).

By your logic, we have to show that there are implementations that
actually enforce that. I.e, it's not enough that implementations in
practice assign a LL address to an interface, we need to show that
there are implementations that prevent the possibility of the
interface ever operating without a LL address. This is unreasonable.

As a more general case, consider a protocol that specifies behavior
X. For example, protocol X must rate limit messages of type Y. Well,
anyone can come along and implement protocol X over raw sockets and
have it flood the network with messages of type Y violating the
required rate limitingf behavior.  By your reasoning, an
implementation of a protocol that doesn't also prevent another
implementation running over raw sockets from violoating the spec would
not be compliant. In general, no implementation can ensure that the
spec is not violated when viewed in this light.

Popping up a level, the arguments being used are fairly legalistic (on
both mine and your side). Based on some of your earlier mail messages
to the WG, it would seem that your real goal here is to do away with
the requirement that all IIDs be 64 bits long and in particular you
would like to remove the 'u' bit from the IID. But this was discussed
explicitly within the WG and there appeared to be little support for
your position.

It is time to advance addr arch to Draft Standard and move on.

Thomas
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