Subject: Re: WG Action ACCEPT [LL23] Don't configure needless LL addresses

From: Mika Liljeberg <[email-masked]>
Date: 02 Mar 2003 17:31:58 +0200

On Thu, 2003-02-27 at 14:55, Erik Guttman wrote:
> Action: Accept

Since no-one else dares bite the bullet I have to ask: how does this
decision follow the issue resolution process? The camps were about even
as far as I could tell. I was expecting to see a compromise proposal on
this. I'd like an answer from the WG chair to this.

> Dissenting Views (summarized by the WG chair)
>     Mika Liljeberg:   
>               His basic point is that this is not foolproof.  There will
>               be problems of leakage of identifers, scope selection,
>               inability to communicate in some cases, etc. and that the
>               transition cases have not been fully worked out.

My view is somewhat misrepresented here. My main concern is that LL23
introduces unnecessary implementation complexity in exchange of new
problens and dubious benefits. I spent some considerable effort trying
to elicit some proof that LL23 has an actual benefit that justifies the
cost. I didn't see such proof. I also agree with the concerns outlined
by Ted and Stuart.

> Notes:
>  (1) It must be noted that LL23 is very close if not identical to the
>      behavior of hosts already supporting IPv4LL configuration today
>      (MacOS9, Windows98 and onward, etc).

That is not a reason to mandate LL23. LL23 merely precludes other
implementation choises, which I regard as favoritism in the
specification.

>   We have operational
>      experience which shows that (a) it is useful, (b) it is not
>      horribly broken.

Statement (a) is questionable. (b) I'm willing to conceed. However, I
have a different implementation approach that is not horribly broken
either.

>  (2) We have WG consensus that issues can arise when there are hosts
>      with more than one scope on the network.  This multi-scoped
>      host will have issues with source address selection and may
>      forward protocol messages with locators, referrals, redirects
>      or addresses in-line off-link.  The host which only supports
>      LL will also be effected if (a) it supports a service and
>      (b) its location is forwarded off link, where the service
>      cannot be reached.  Implication:  Mixed scopes *do* present
>      a problem.

There probably is a common understanding that scoped addressing presents
some problems. However, this is not an argument for or against LL23. I
don't believe LL23 helps solve the problem to any significant degree and
it has a cost that is not attractive.

>  (5) In response to Mika's concern:  We realize there are potential
>      issues when hosts have multiple address scopes configured.  This
>      state with known problems is *bounded* in that hosts will only
>      experience these problems during transition.

This does not address my concerns at all. I spent some considerable time
trying to elicit proof that there is a problem in our current
implementation approach, now precluded by LL23, and received none.

>  (6) In response to Stuart's concern:  Support for networking in 
>      misconfigured networks is not a work item on the charter.

Zero configuration is in the charter. Support of routable addresses is
not. Yet the WG went there and created a solution, which prevents zero
configuration in some cases.

>   It
>      is unfortunate that we cannot offer a solution to this problem,
>      but to do so would leave the can of worms open for an indefinite
>      period of time.

This statement is completely unfounded. Proponents of LL23 failed to
show any real problems with the existing specification.

>  (7) Accepting LL23 goes a long way toward answering IESG concerns.

I truly hope so. At the moment that would be the only upside I can see.

Well, enough on LL23 I guess. Let's move on.

	MikaL