Subject: Re: Proposed resolution to LLMNR Issue 21 (and 7)

From: Markku Savela <[email-masked]>
Date: Tue, 18 Mar 2003 08:57:34 +0200

> From: Bernard Aboba <[email-masked]>
> > I think this is getting really complex. I suggest that LLMNR only
> > deals with link local addresses. Which brings me to the Issue 7
> 
> We don't have that option for IPv4. Zeroconf WG has decided that for IPv4,
> a linklocal address isn't advertised if a routable address is available.

..and you know my opinion: Zeroconf WG made wrong decision. In my view
the opinions of people whose agenda was to cripple LL4, won.

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From: Mika Liljeberg <[email-masked]>
Date: 18 Mar 2003 09:50:50 +0200

On Tue, 2003-03-18 at 03:54, Bernard Aboba wrote:
> > How is LLMNR supposed to find out whether an address is on link or
> > not?
> 
> Presumably it looks at the routing table.
> 

That decision has problems that zeroconf has not yet been able to solve.
In a nutshell: two nodes with different configured netmasks are unable
to communicate on the local link, unless they also have link-local
addresses. [There are ad-hoc scenarios where this can easily happen.]

At this point, it would be prudent to advertise all IPv4 addresses a
node has and leave it to the client node to choose an appropriate
address.

> > > Add the following text to section 4:
> >
> > > "[4] A responder with both linklocal and routable addresses
> > >    SHOULD respond only to LLMNR queries for A/AAAA RRs for
> > >    the routable address. This encourages use of the routable
> > >    address for establishment of new connections."
> >
> > I would go the other way: LLMNR should only return link local
> > addresses, never routable address.
> 
> Since for IPV4 we'll not be able to do that, the question is whether IPv6
> should behave differently.

With IPv6 the right thing, in my opinion, is to advertise link-local
addresses only. All IPv6 nodes have link-local addresses and on-link
routes for them, so link-locals will always work. However, as with IPv4,
configured addresses are not guaranteed to work for link-local
communication unless all nodes happen to have the same on-link prefixes.

	MikaL