Re: [Autoconf] issues with draft-baccelli address model

[Alexandru Petrescu <alexandru.petrescu at gmail.com>]

sratliff a écrit :
[...]
> > draft-baccelli says:
> > > Note that while link-local addresses are assumed to be "on link",
> > > the utility of link-local addresses is limited as described in
> > > Section 6.
> > The word "limited" strikes.
>
> Nonsense. "utility.. is limited" is not the same as "must not be
> used".

Would you agree to say "the utility of /128 prefixes is limited"?

> > draft-baccelli says:
> > > o  A subnet prefix configured on this interface should be of
> > > length /128.
> > The link-local prefix of IPv6 LLs is fe80::/10, and not /128.
>
> The key word in that sentence is SHOULD. It does not say MUST.

Well, LLs are a SHOULD on many interfaces.  A SHOULD and and a SHOULD
NOT could give a "MAY":  "a /128 prefix on this interface MAY be /128".
(and I invite implementers to do it and report back problems thank you).

> > draft-baccelli says:
> > > o  Any [IPv4] subnet prefix configured on this interface should
> > > be of length /32.
> > Yet the prefix of the IPv4 LL is 169.254/16, and not a /32.
>
> Again, the sentence says SHOULD. Not MUST.

Again, a MAY would be a better fit.

> > draft-baccelli says:
> > > Note that the use of IPv4 link-local addresses [RFC3927] in this 
> > > context should be discouraged for most applications
> > "Discouraged" means discouraged.  And which "context"?  The word 
> > "context" appears precisely once in the draft.
>
> Precisely. "Discouraged" means discouraged. It doesn't mean "cannot".
> And again, the sentence contains the word SHOULD. It does not say
> MUST.

I believe that "dicouraged" fits better the use of host-based routes
(the "/128" prefix recommendation) for a variety of reasons, making them 
limited use too: (1) it doesn't scale to large domain, (2) can't connect 
to the Internet, (3) consumes more ressources than /64-or-shorter 
prefixes (cycles: instead of average 64 bit comparisons you use a sure 
128 bit comparisons, memory: instead of one entry covering several 
destinations you use an entry for each destination in each router).

It sounds as we have it completely reverse, and "MAY" may solve it.

Alex