RE: There are claims of ambiguity over what is a link-local address

>From the thread cited:
> Or did the authors really intend that most of fe80::/10
> remain unused, and *only* a single /64 at the very
> start of fe80::/10 would be valid?

Right.

The intent was a bit clearer in RFC 3513, which RFC 4291
obsoletes.  Section 4 has:

> The initial assignment of IPv6 address space is as follows:
>
> Allocation                            Prefix         Fraction of
>                                       (binary)       Address Space
> -----------------------------------   --------       -------------
...
> Link-Local Unicast Addresses          1111 1110 10   1/1024
> Site-Local Unicast Addresses          1111 1110 11   1/1024

And yet a bit clearer in RFC 2373 (and RFC 1884 the original).
It has the same as above plus:

> The only address prefixes which should be predefined in an
> implementation are the:
>
>   o Unspecified Address
>   o Loopback Address
>   o Multicast Prefix (FF)
>   o Local-Use Prefixes (Link-Local and Site-Local)
>   o Pre-Defined Multicast Addresses
>   o IPv4-Compatible Prefixes

So they define the /10 as the link local *prefix*,
within which any *addresses* have to fall into the /64.
The rest of the /10 is unused but is still defined as link-local
scope.

-Dave

> -----Original Message-----
> From: ipv6-bounces@ietf.org [mailto:ipv6-bounces@ietf.org] On Behalf Of
> Alexandru Petrescu
> Sent: Monday, May 07, 2012 12:51 AM
> To: ipv6@ietf.org
> Subject: Re: There are claims of ambiguity over what is a link-local address
> 
> That ambiguity around the prefix length /10 vs /64 of a link-local address
> should be clarified.
> 
> If clarified, among other advantages, it would  allow to write C code which,
> when typing "ifconfig eth0 add fe80::1" it would know to fill in the prefix
> length by itself, and not wonder about which length should it be.
> 
> Alex
> 
> Le 07/05/2012 08:56, Brian E Carpenter a écrit :
> > On 2012-05-07 00:59, Mark Andrews wrote:
> >> See the nanog thread starting here:
> >> http://mailman.nanog.org/pipermail/nanog/2012-May/048079.html
> >>
> >
> > I'm sure the intention was to reserve the entire /10 prefix but it's
> > correct that the RFC is not clear about this. Seems like an erratum is
> > needed.
> >
> > Brian
> > --------------------------------------------------------------------
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