Subject: Re: globally unique site local addresses

From: Richard Nelson <[email-masked]>
Date: Thu, 21 Nov 2002 12:06:36 -0500

Add to free - easy to obtain for non connected sites.  1918 addresses
are easy to obtain.

Richard

----- Original Message -----
From: Christian Huitema <[email-masked]>
Date: Thursday, November 21, 2002 11:38 am
Subject: globally unique site local addresses

> During the WG meeting, we agreed to work on the definition of a 
> globally unqiue site local addressing architecture, so that we can 
> eventually deprecate site local addresses. I am listing here so far 
> a couple of points that were made by different speakers, as an 
> introduction to the debate:
> 
> * we want to remove ambiguity, which is the root cause of many 
> problems occuring when scoped addresses leak.
> 
> * we may or may not want to prevent routing of these addresses 
> between sites. I guess we should certainly prevent routing between 
> non-consenting sites.
> 
> * we definitely want the addresses to be provider independent, so 
> they can survive renumbering or intermittent connectivity.
> 
> * indeed, it would be desirable that the addresses be usable in 
> sites that are not connected.
> 
> * and we would definitely want the addresses to be free.
> 
> One of the main point of contention regarded routing. I guess that 
> the consensus is, "just like site local addresses." We don't want 
> to prevent usage in connected sites, but we expect that in these 
> sites the hosts will also have provider based addresses, and that 
> traffic routed out of the site will use the provider addresses.
> 
> Now, I guess we have to work from there. 
> 
> -- Christian Huitema
> 
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---

From: Tim Chown <[email-masked]>
Date: Thu, 21 Nov 2002 18:38:20 +0000

> Add to free - easy to obtain for non connected sites.  1918 addresses

I have reservations here.  I don't see how such prefixes, with the
associated administration/registry work, will be offered for free.
There may also be a few orders of magnitude more such prefixes requested
than there are SubTLAs.  Or do people feel such requests will be very
limited?   Who can manage this for no cost? 

So people will just pick their own prefixes at random, or use addresses
in the site local space (which in a small network will be easier to
remember and use for configs).  Are there advantages to uniqueness 
(to the user) beyond some guarantee of avoiding clashes when merging 
sites?  I doubt this is something I would care about in my home network, 
if it had intermittent connectivity and/or dynamic ISP-assigned /48's, 
and I wanted some kind of persistent address space to use internally).

Whatever we offer has to be more attractive, as Christian said today,
and if it's not free, it won't be.  

If DSL providers offer static /48's, we can reduce requirements for 
such independent address space in home networks, so the above may be moot.

Tim

---

From: Charlie Perkins <[email-masked]>
Date: Thu, 21 Nov 2002 11:08:00 -0800

Hello Tim,

Maybe it could be done almost for free.

Maybe there could be a web page under the IANA web
page where a network administrator could get the "next"
site-local prefix.  This would be rate-limited so that only
a few prefixes would be given out per second, and so on.

It seems like it would work, at least well-enough to be
given a try.  It would not require very much administration
on the part of IANA (or whoever agreed to host the
web page).

Of course, this only solves the one problem of guaranteeing
global uniqueness for the site-local prefixes, and the
other problems remain.

Regards,
Charlie P.

---

From: Richard Nelson <[email-masked]>
Date: Fri, 22 Nov 2002 05:16:19 +0000

> and if it's not free, it won't be.

I'm not quite sure what your conclusion is as this sentance appears to
contradict your opening statement.  Despite that, I agree with you, it
should be free to be attractive and it can't be free because of the
uniqueness requirments.  The real problem comes with connected sites so
perhaps we have to ensure that all users get an allocation whenever they
get an ISP sites.  For non-connected sites I think that cheap enough
that the cost is not generally a concern will be the best we can really
hope for.

Richard.

---

From: Jari Arkko <[email-masked]>
Date: Thu, 21 Nov 2002 19:37:56 +0200

> on the part of IANA (or whoever agreed to host the

I also thought about this. An automatic protocol to go get
a new site-local prefix... in my approach there was some kind
of a "key" however that the requesting entity had to provide.
This key could be a physical address, global IP address, MAC
address, or something like that. A new request from the same
"key" would give you back the same site-local prefix. This would
prevent a trivial depletion attack on the pool of prefixes. Yeah,
rate-limitation helps but I don't think it solves the problem.

But then I started to think about this in more detail. Remember
that our requirement was to be able to deal with disconnected sites.
I don't see how a disconnected site is going to the IANA web for
a prefix ;-) Or do we have to assume a human who helps the site
to get a prefix? In my opinion, that would prevent many useful
scenarios...

Jari