Subject: Regarding site-local addresses

From: Brian Zill <[email-masked]>
Date: Mon, 29 Nov 1999 13:46:26 -0800

I changed the subject line to better reflect the issue.  I think site-local
addresses, or something very much like them, is useful and will work fine.

Jim Bound writes:
> Christian Huitema writes:
> >I have always considered the "site address"
> >an atrocious leftover of Net 10, and the more
> >I see this discussion unfolding, the stronger my
> >conviction.

I believe that if we do not specify site-local addresses specifically, we
will end up with the equivalent of IPv4's net 10 anyway, due to marketplace
pressures.  The "new devices" or "home automation" crowd will want all of
their IPv6 enabled dishwashers, water heaters, light switches, stereos, etc.
to be able to talk to one another without making Joe and Jane Average get an
Internet connection and global addresses.  Since multiple links will likely
be in use in the home (power-line, telephone-line, Ethernet, multiple types
of wireless), link-local addresses will not work.  If we don't define
site-local addresses now, manufacturers of such devices will either lobby
for them, use some random prefix, or simply not use IPv6.

> >I can swallow the unidentified link address -- 
> >such address are necessary for autoconfig.
> >But I have a very hard time trying to understand
> >what exactly is good in the site address format:
> 
> I agree 100%.

The good thing about specifying site-local addresses now is that all IPv6
routers will, by default, understand that site-local addresses must not be
forwarded outside of the site.  Introducing a "net 10" at a later date is
more likely to result in leakage of such addresses into the global internet
(or between "net 10" sites).
 
> >1) It does not exactly simplify autoconfig,
> >   since one has to program some form of site
> >   identifier in the nodes, 
> 
> Exactly.

No, a single-sited end node doesn't need to know anything about site
identifiers.

> >2) It cannot be stored in a directory,
> 
> Exactly.

No, a site-specific directory can hold site-local addresses.

> >3) It should not be routed, but then it has
> >   to be propagated for the needs of mobile nodes,
> 
> Exactly.

I don't claim to be a mobile-IP expert, but I thought this was a solved
problem in the mobile-IP draft.

> >4) It is very hard to handle in multisited nodes.
> 
> Exactly.

I don't see this either, but I guess it depends upon your definition of
"very hard".  Tagging every interface in a routing node with a node-specific
site-id and then only forwarding between like site-ids seems pretty
straight-forward.  So does only allowing end node originated packets to go
out via interfaces with a site-id that matches the one in the sin6_scope_id
field.  Our implementation does both of these today.

Everything else is UI/API.  The only hard part here has been getting all the
makers of stacks for "old style" computers (the kind people sit in front of
and type at) to agree on the UI/API.  The "new device" crowd could care
less.  Site-locals will work just fine for them.  All they need is already
in RFC 2373.

> IPv6 can work but I strongly urge you to help me
> and anyone else shoot these site-local addresses
> in the head.

IPv6 does work.  So do site-local addresses.  I strongly urge everyone to
keep them as part of the standard or we'll be needlessly excluding many
potential uses of IPv6.

> We have enough global address space with IPv6 that
> we can re-create a Net-10 within the IPv6
> exponential number of addresses.

Yes, we could do that.  This is basically what the site-local prefix does
today.  I see advantages to establishing it now (stated above) and no
advantage to waiting.

In summary, I see many potential uses for site-local addresses.  Making
renumbering easier is not the only (or maybe even a good use) of site-local
addresses.  We should consider that they are most useful outside of the
corporate workplace PC/workstation environment, where having global
addresses is not a given.

--Brian 
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---

From: Jim Bound <[email-masked]>
Date: Mon, 29 Nov 1999 17:52:48 -0500

>addresses, or something very much like them, is useful and will work fine.

good change.

>for them, use some random prefix, or simply not use IPv6.

Don't agree, global addresses will work.  There is enough of them and the 
only reason Net 10 will exist.

>(or between "net 10" sites).

Correct use of global addresses will do the same thing.

>No, a single-sited end node doesn't need to know anything about site

For a multisited node this is necessary.

>No, a site-specific directory can hold site-local addresses.

No one on this appears to want them in DNS any place else is another
discussion and proposal.  Also their identity would need to be defined.

>problem in the mobile-IP draft.

If you keep going back to the Home Agent yes otherwise it has the same
problem any node would have with a duplicate address across different
sites.

>field.  Our implementation does both of these today.

Thats not the problem or how I interpreted Christian's mail.  How are
they defined so we can all use them interoperably.

>less.  Site-locals will work just fine for them.  All they need is already

Simply don't agree.  

Where is the draft that discusses the use of site-local addresses? Do
you think its Erik's?  If so do you agree we should do that?  We can't
do it 10 different ways.

>keep them as part of the standard or we'll be needlessly excluding many

They do not work in a standard interoperable manner and the IETF has no
spec on their use other than Eriks.

Are you saying we have no work to do on site-local addresses in the
working group?

>today.  I see advantages to establishing it now (stated above) and no

We just don't agree.

>addresses is not a given.

Net 10 is not something customers did other than IPv4 address space is
exhausted.

/jim

---

From: Peter Tattam <[email-masked]>
Date: Tue, 30 Nov 1999 12:00:34 +1100 (EST)

> for them, use some random prefix, or simply not use IPv6.

Hmm. There's a tiny hole in this argument in that there is a possibility that a
customer might want a largish intranet that traverses sites.  Site local
addresses would not be able to be used because the routers know not to forward
such packets.  So there would still exist the need for a net 10 style prefix
that routers would not restrict.

I think there probably should be an in-between solution that by default is not
routed between routers, but if needs arise such a switch can be turned off
should a customer need the facility.  Leaking would be minimized because you
would explicitly have to enable the feature.

> addresses is not a given.

I generally agree with your arguments.  Site local addresses have my vote.

Peter

--
Peter R. Tattam                            [email-masked]
Managing Director,    Trumpet Software International Pty Ltd
Hobart, Australia,  Ph. +61-3-6245-0220,  Fax +61-3-62450210