Re: Last Call: <draft-ietf-6man-rfc4291bis-07.txt> (IP Version 6 Addressing Architecture) to Internet Standard

[David Farmer <[e-mail]>]

On Fri, Feb 17, 2017 at 6:46 AM, tom p. <[e-mail]> wrote:

> From: <[e-mail]>
> To: "james woodyatt" <[e-mail]>
> Cc: <[e-mail]>; "6man WG" <[e-mail]>;
> "IETF-Discussion Discussion" <[e-mail]>; <[e-mail]>
> Sent: Friday, February 17, 2017 7:44 AM
>
> > James,
> >
> > 4291:
> >    For all unicast addresses, except those that start with the binary
> >    value 000, Interface IDs are required to be 64 bits long and to be
> >    constructed in Modified EUI-64 format.
> >
> > 4291bis:
> >    IPv6 unicast routing is based on prefixes of any valid length up to
> >    128 [BCP198].  For example, [RFC6164] standardises 127 bit prefixes
> >    on inter-router point-to-point links.  However, the Interface ID of
> >    all unicast addresses, except those that start with the binary
> value
> >    000, is required to be 64 bits long.  The rationale for the 64 bit
> >    boundary in IPv6 addresses can be found in [RFC7421]
> >
> > Proposal:
> >    IPv6 unicast routing is based on prefixes of any valid length up to
> >   128 bits [BCP198]. However, as explained in [RFC7421], the Interface
> ID
> >    of unicast addresses is generally required to be 64 bits in length,
> with
> >    exceptions only provided in special cases where expressly
> recognised
> >    in IETF standards track documents.
> >
> > I think that's a good proposal.
> > Perhaps with s/is generally required to be/are/
>
> Ole
>
> I would go further on the grounds that this is still somewhat woolly.  I
> would say
>
> Proposal':
>   IPv6 unicast routing is based on prefixes of any valid length up to
>  128 bits [BCP198]. However, as explained in [RFC7421], the Interface ID
>   of unicast addresses is required to be 64 bits in length; any
> exceptions
>   must be specified in IETF standards track documents.
>
>
> It would be nice to have something IANA-like with different categories
> of what can update what, with this being at the higher level, the bar
> set higher for an Interface ID that is not 64 bits in length, but when
> we say 'standards track' we are calling for IETF consensus and IESG
> approval and it is hard to see what more could be called for, unless we
> say that this is architectural and so the IAB must approve it!
>

I don't think the intent of that language is to define or constrain our
processes.  As I see it, the purpose of that text is to make it clear the
IID length is and has always been a parameter, which operators are
constrained by this text to to set at 64 bits, but this value cannot be
embedded as a magic value in code, because there are cases where its not 64
bits, even beyond addresses that start with 000.

I'll conceded, whether 64 bit boundary is a requirement, or more
appropriately a recommendation, is probably beyond the scope of a bis
document. However, clarifying who the requirement is directed at, is most
certainly within scope and I think imperative.  I have never heard anyone
claim this requirement is to be put in code, in fact quite the contrary,
everyone seem to agree it should NOT be put in code, and therefore by
reduction it is intended to be an operational constraint.  Or in other
word, the requirement is primarily directed at operators of IPv6 networks,
and not implementers of IPv6.

The following takes the essential text from from RFC4291, rearranges it a
little and wraps it with clarifying language, which is what we should be
doing in a BIS document.  Now those of us that want more significant
changes, it's incumbent on us to write standards track documents, and get
consensus for them, like it has always been.  But in the mean time
implementations are put on notice that 64 bit boundary is primarily an
operational constraint and not something that can safely be embedded in
code.

So I suggest the following;

   IPv6 unicast routing is based on prefixes of any valid length up to 128
   [BCP198].  However, as discussed more thoroughly in [RFC7421], the length
   of the Interface ID is a parameter, that is required to be 64 bits for
   all unicast addresses, except those that start with the binary value 000,
   with additional exceptions provided in other standards track documents.
   Other than it's implications to Stateless Address
Autoconfiguration(SLAAC)
   [RFC4862], this requirement's primary effect is operational, as
   implementations of IPv6 must not ignore or override the local
   configuration of this parameter, even if it conflicts with this
   requirement. The rationale for the 64 bit boundary in IPv6 addresses
   can be found in [RFC7421].

However, the text we have been discussing is the second paragraph of
section 2.4 of the draft, but if preferred these last two, sentences could
be broken out and integrated in section 2.4.1

Leaving the second paragraph of 2.4 something like this;

   IPv6 unicast routing is based on prefixes of any valid length up to 128
   [BCP198].  However, as discussed more thoroughly in [RFC7421], the length
   of the Interface ID is a parameter, that is required to be 64 bits for
   all unicast addresses, except those that start with the binary value 000,
   with additional exceptions provided in other standards track documents.

With the forth paragraph of 2.4.1 something like this;

   As noted in Section 2.4, the length of the Interface ID is a parameter,
   that is required to be 64 bits for all unicast addresses, except those
   that start with the binary value 000, with additional exceptions
   provided in other standards track documents. Other than it's
   implications for Stateless Address Autoconfiguration(SLAAC)[RFC4862],
   this requirement's primary effect is operational, as implementations
   of IPv6 must not ignore or override the local configuration of this
   parameter, even if it conflicts with this requirement. The rationale
   for the 64 bit boundary in IPv6 addresses can be found in [RFC7421].

Thanks


> Tom Petch
>
> > Best regards,
> > Ole
> >
> >
>
>
-- 
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