Re: [v6ops] Scope of Unique Local IPv6 Unicast Addresses (Fwd: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt)

[Mark Smith <[e-mail]>]

On Fri, 19 Feb 2021, 11:37 Brian E Carpenter, <[e-mail]>
wrote:

> So, my thought (and it belongs on this thread OR the 'IPv6 addressing:
> Gaps?' one) is something like:
>
> We should abolish, delete, expunge and deprecate the word "scope" from all
> IPv6 documents. It clearly doesn't have an agreed meaning, so it is worse
> than useless.
>

I think the word scope is fine.

The problem is that by itself it doesn't specify what thing the scope is
applying to, and people aren't explicitly saying what that scope they're
referring to. "Global scope" - scope of what?

ULAs (and addresses in general) have at least two different scopes:

- scope or domain of intended uniqueness

- scope or domain of intended forwarding within a network or across a set
of networks

There's others, for example, portions of the GUA space will have RIR
assignment scopes or IETF/IANA assignment scope.


"Scope" and "domain" seem to almost be synonyms. "Global domain", without
specifying what "domain" refers to, would have the same problems as the
term "global scope".

Regards,
Mark.



> All addresses have a region of reachability. This may be confined to a
> single "link" (whatever a "link" means), some type of limited domain (such
> as, but not limited to, a "site" (whatever a "site" means)), or to a large
> part of the Internet as a whole (knowing that there is in reality no such
> thing as "the" Internet.)
>
> LL addresses MUST NOT be used off a given L2 link.
> ULAs MUST NOT be routed outside a given limited domain.
> GUAs MAY be routed anywhere.
>
> (MANETs and other mesh networks don't fit in there very well.)
>
> Regards
>    Brian
>
> On 19-Feb-21 12:58, Fernando Gont wrote:
> > On 18/2/21 20:39, Manfredi (US), Albert E wrote:
> >> -----Original Message-----
> >> From: ipv6 <[e-mail]> On Behalf Of Fernando Gont
> >>
> >>> Well, this is a spec inconsistency. You have one spec (RFC4007)
> defining
> >> "scope" and "global scope", and another specs:
> >>>
> >>> a) making use of the same terms in an incorrect way, or,
> >>>
> >>> b) employing same terms but with a different definition.
> >>>
> >>> i.e., either the definition in RFC4007 is incorrect, or the use in
> >> RFC4193 and implicit use in RFC4291 is incorrect.
> >>
> >> You can also argue, if there are prefix bits sent in the clear, and
> those prefix bits are used to send the packets to a pre-determined gateway,
> and that gateway is then used to decrypt all of the remaining address bits,
> then route packets through a walled garden intranet with global span, then
> global scope could still apply.
> >
> > "global span" is defined as "Internet-wide" span. i.e., if an address
> > does not unambiguously specify an interface Internet-wide, it's not
> > global scope as per RFC4007.
> >
> >
> >
> >> Just sayin'. These still aren't like RFC 1918.
> >
> > The only practical differences I see with respect to rfc1918 are:
> >
> > 1) ULAs are not intended to be used with NAT.
> > However, were RFC1918 strictly specified to be employed along with NAT?
> > Besides "not indended" != "won't be".
> >
> > 2) ULAs are intended to have a small probability of collision when a
> > subset of ULA-based networks are interconnected.
> >
> > This is the product of mandating that some bits are generated from a
> > PRNG, plus the fact that ULAs have more bits than their RFC1918
> counterpart.
> >
> > If I have missed any other differences, please enlighten me. :-)
> >
> > Thanks,
> >
>
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