Subject: Responses so far

From: Stuart Cheshire <[email-masked]>
Date: Fri, 29 Nov 2002 12:24:04 -0800

It's Thanksgiving, so most people are off work, but here is a summary of 
the responses I've received so far:

People willing to argue in support of Option 1
(Set TTL=255 on transmit, check TTL==255 on receipt)
Stuart Cheshire
Jay A. Kreibich
Daniel Senie
Martin Layley
Joshua Graessley
Brad Hards
Vincent Lubet
Erik Guttman

People willing to argue in support of Option 2
(Set TTL=1 on transmit, check TTL==1 on receipt)
RJ Atkinson

People willing to argue in support of Option 3
(Set TTL=anything on transmit, don't check TTL on receipt)
Thomas Narten

People willing to argue in support of Option 4
(User-configuration for "Zero Configuration" devices)
(None)

If your name is not listed, and you feel you have a technical opinion 
you'd be willing to support, please send mail to the list or to me 
privately. Please try to keep your email short and to-the-point. For 
example, Keith Moore has written a great volume of email, but I can't 
tell which of these positions (if any) he is advocating.

Don't assume the decision is already made; it's not. This is not a vote. 
I'd like to try to get all interested parties involved here, and show 
that an IETF Working Group is still able to arrive at a decision when it 
has to.

If anyone is wondering why I listed Thomas Narten's name under option 3 
(don't check) instead of option 2 (Set TTL=1), that's because if no one 
is checking the TTL, it doesn't matter what you set it to. The RFC can 
say what it likes about what the TTL "MUST" be set to, but it is 
irrelevant if no one is checking. Vendors will get it wrong, and their 
products will work fine because no one is checking the TTL, and they will 
ship those products. Even if someone complains to the vendor that the TTL 
is wrong, they'll just laugh. Few vendors of $100 devices are willing to 
waste engineering resources fixing a "bug" that has no effect on how well 
their product works. In many cases, the firmware for a device was written 
by a contractor, so the company couldn't fix the bug even if they wanted 
to. In some cases, products remain in use long after the company that 
made them has gone bankrupt, so there's no one to even complain to. In 
short, any discussion of what the TTL should be set to is only of 
practical value if we've already decided that receivers are checking that 
value.

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

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From: Keith Moore <[email-masked]>
Date: Fri, 29 Nov 2002 15:59:19 -0500

> tell which of these positions (if any) he is advocating.

That's because you're trying to make me support one of three positions
that you've arbitrarily chosen, and I don't think the set of alternatives 
you've proposed adequately covers the solution space.   

Also you seem to be trying to address a deficiency in the spec that was 
identified by IESG by appealing to group consensus.  An answer of the 
form "we have consensus on TTL=255" without justification is not 
useful - what is required is a response to IESG's concerns.  Trying to 
appeal to WG consensus is in some sense dodging IESG's question.

> is checking the TTL, it doesn't matter what you set it to. 

Routers check.  Whether it's relevant for routers to check is a different
question, but let's not gloss over the fact that the reason for suggesting
TTL=1 on transmit is so that routers will refuse to forward them.

Keith

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From: "John C. Welch" <[email-masked]>
Date: Fri, 29 Nov 2002 16:56:34 -0500

> tell which of these positions (if any) he is advocating.

I'll go with 255, it's already in the proposal, I haven't seen any real
validity to changing it other than a minor routing issue which is handled
better in other ways.

Inertia's a physical law, that works for me.

john

-- 
John C. Welch
Consultant III
Administrative Computing
(617) 253 - 1368 work
(508) 579 - 7380 cell
bynkii2          AIM

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From: "John C. Welch" <[email-masked]>
Date: Fri, 29 Nov 2002 16:58:51 -0500

> TTL=1 on transmit is so that routers will refuse to forward them.

But that's a router issue, not a LL issue. The question is, is 255 or 1
better for LL. If 1 is better, then why? The router issue is irrelevant, as
they can be updated for Zeroconf along with everything else.

john

-- 
John C. Welch
Consultant III
Administrative Computing
(617) 253 - 1368 work
(508) 579 - 7380 cell
bynkii2          AIM