Subject: Re: LLMNR interoperability with Rendezvous?

From: Stuart Cheshire <[email-masked]>
Date: Mon, 6 Oct 2003 17:28:15 -0700

>You shipped code against an uncompleted specification and as it goes
>there was development on the TTL issue and consensus changed. Some
>room has been provided to review the issue but the fact that there
>is code shipped against an uncompleted specification is not a valid
>argument in that review, only an argument to revisit the issue.
>
>Thus you on your own and with known consequences decided to ship code
>against uncompleted specification.
>If your company wants interoperabilty they can update distributions,
>and possibly at the same time a put in a kludge to talk to the
>old implementations.
>
>         Sorry but that is the cold facts.
>         Olafur DNSEXT co-chair.

Ólafur, you're mixing up two issues.

In his pejorative "freshman engineering" analogy, I thought John 
Schnizlein was suggesting that Apple disregarded the Working Group 
consensus and intentionally did the opposite for no good reason (though 
perhaps that's not what he was saying). I was just pointing out one 
simple fact. At the time we shipped, apparent Working Group consensus, as 
reflected in the drafts at that time, was that the TTL should be 255, and 
that's exactly what we did. I did *not* say that Working Groups cannot 
change consensus -- as we know, they do that all the time.

On a related subject, I asked a while back if any LLMNR implementers had 
tested to see if their implementations do or do not interoperate 
successfully with Mac OS X. Specifically, if a LLMNR query is sent to 
224.0.0.251:5353 with an IP TTL of 255, do Mac OS X machines on that link 
respond correctly?

Stuart Cheshire <[email-masked]>
 * Wizard Without Portfolio, Apple Computer, Inc.
 * www.stuartcheshire.org

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---

From: John Schnizlein <[email-masked]>
Date: Mon, 06 Oct 2003 22:40:09 -0400

>change consensus -- as we know, they do that all the time.

My plea to preserve the semantics of TTL was not pejorative "freshman engineering". The justification of TTL=255, based on misreading multicast implications, was rejected in the discussion of the issue in the ZeroConf WG.

My complaint was that the consensus in the ZeroConf WG in favor of preserving the meaning of TTL, with TTL=1 for no hops (link local) in combination with Christian's accommodation of other TTLs for compatibility where an application needed something else, was reversed by the Chair based on private arguments after the issue was officially closed. I never said Apple disregarded WG consensus in deploying Rendezvous using TTL=255. I did raise the concern when the ZeroConf WG reversed the rough consensus in favor of TTL=1, that the LLMNR draft had settled on it.

My personal background with Apple goes as far back as 1985, when I bought Kinetics FastPaths to connect Macintosh networks on the campus network I designed and managed. I have owned Macintosh computers since 1987, and designed an operated an AppleTalk network from 1989 until 1996. I have been a consistent supporter of the migration of AppleTalk to IP throughout this period. I admired both the Macintosh and NeXT designs and bought systems, either personally or for my various employers reflecting these opinions. This is not about me.

As in the Middle-East, any position can be argued by claiming the basis at a time long enough ago. The history is less important than preserving the foundation of the Internet Protocol. I recall your statements that you had advocated TTL=1 for the reasons it gained rough consensus in the ZeroConf WG (prior to the reversal). Your argument was that Apple deployed the draft specification of TTL=255. Now that the mistaken multicast justification for TTL=255 is deprecated, and the impracticality of demanding that all (previously) installed routers block forwarding of the recently (in the larger picture) LL prefix in order to keep link-local traffic local has been recognized, please re-join the advocacy of TTL=1 for link-local.

With respect,
John