Re: A proposal for draft-ietf-6man-rfc4291bis-07

David Farmer <farmer@umn.edu> Fri, 03 March 2017 02:39 UTC

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From: David Farmer <farmer@umn.edu>
Date: Thu, 2 Mar 2017 20:39:31 -0600
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Subject: Re: A proposal for draft-ietf-6man-rfc4291bis-07
To: "Manfredi, Albert E" <albert.e.manfredi@boeing.com>
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On Thu, Mar 2, 2017 at 8:05 PM, Manfredi, Albert E <
albert.e.manfredi@boeing.com>; wrote:

> From: David Farmer [mailto:farmer@umn.edu]
>
> >> Brian E Carpenter <brian.e.carpenter@gmail.com>; wrote:
>
> >> Agreed. And I think there are actually two things to say here:
> >>
> >> 3.1. Any IPv6-over-foo spec must specify a recommended IID length.
> >> 3.2. In the absence of such a spec, the recommended IID length is
> >> 64 bits.
>

How about, IIDs are REQUIRED to be 64 bits unless overridden by an
IPv6-over-foo spec?


> >> Again, that breaks no running code, and it respects the architectural
> >> statement that prefix_length + IID_length == 128, and the use of CIDR
> >> routing and variable-length subnet masks.
> >>
> >>    Brian
> >
> > I'd be fine with that, but others seem to feel otherwise. Lorenzo
> > and James?
>
> That's why it's called "consensus." As opposed to unanimity.
>
> > However, if a provider only delegates a /64, this new text ensures that
> > prefix could be further subnetted down below /64 using manual config or
> > possibly DHCPv6.
>
> Exactly. So, how can we allow RFC 4291 bis to say that 64-bit IIDs are
> REQUIRED? We can't. That was my original point.
>
> Bert
>

Because, it doesn't say IIDs are themselves required.  In fact it says "at
a minimum, a node may consider that unicast addresses (including its own)
have no internal structure". IIDs are just that internal structure of an
address, which is by that text is OPTIONAL.  Therefore, it is only saying
if you use an IID it must be 64 bits.

And I'd now suggest it should say, if you use an IID it must be 64 bits
unless overridden my an IPv6-over-foo spec.


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