Subject: Re: New issue: When to configure a LL address

From: Stuart Cheshire <[email-masked]>
Date: Wed, 12 Mar 2003 23:24:03 -0800

Ralph Droms wrote:
>As an example, at present I don't ever want my laptop to configure an 
>IPv4ll address.  I have no way to make sensible use of IPv4ll addresses, 
>and any attempt by my laptop to configure an IPv4ll address is wrong and 
>will cause me to spend cycles trying to debug a network problem.

I think you need to think further ahead.

Today, if you have no other devices that can use IPv4LL addresses, then I 
agree that your laptop can't make much use of them.

However, try to think a year from now.

Your laptop does IPv4LL.
Your printer does IPv4LL.
You are giving a presentation in ten minutes and you need to print your 
notes to hand out. Your DHCP server's power supply has overheated and 
burned out, and you don't have time to fix it.

Are you really going to complain if the printer and laptop configure 
IPv4LL addresses and you are able to print and get to your meeting on 
time?

You are right that it would be good to have your laptop display an alert 
saying, "Your computer has lost Internet connectivity. Only communication 
with local devices will be possible." I think that's a great idea, and we 
should do it on OS X, but let's not confuse user-interface design with 
protocol design.

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

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From: "John C. Welch" <[email-masked]>
Date: Thu, 13 Mar 2003 07:39:36 -0500

> However, try to think a year from now.

How about months from now? Benetton is implementing short range RF tagging
for inventory control. Bet they aren't using IP. Why? Because without a v4LL
standard they have to build a dhcp client into a chip in your underwear,
that has a range of about 1.5 meters and is a 1K eeprom.

This is the *perfect* situation for LL. There is NO earthly, sane reason for
clothing to have a routable address. Besides, in a week, Benetton would eat
the v4 space alive anyway. All you need is a unique address and a chip GUID.
The ip address only has to be unique for the truck, the shop, etc, and then
*only* when it's in range of a reader, so that it can establish a connection
for the reader.

And it's not just clothing. Food chains are looking at this *very*
seriously, as are retail merchants of all stripes. Wouldn't it be nice if
they could just use a standard transport mechanism, instead of rolling their
own?

john

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

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From: Ralph Droms <[email-masked]>
Date: Thu, 13 Mar 2003 08:10:37 -0500 (EST)

I don't doubt that months from now or a year from now *someone* will want
to use IPv4LL addresses.

*I* don't use IPv4LL addresses today.  I will be happy to use them at a
time that's appropriate for me.  Until I start using IPv4LL addresses, I
don't want a protocol spec or other devices using IPv4LL addresses or IPv4
implementations to have a negative impact on my use of globally routed
addresses.

Furthermore, I'm sure there are a lot of IP users (most of whom don't know
they are even using IP) who are in the same situation.

Stuart mentioned that we should keep the protocol and the user interface
separate.  OK, but current implementations of IPv4LL have had the same
inadequate user interface for a number of years, and I see no indication
that future implementations will have a better interface.

So, knowing that existing IPv4LL implementations have a negative impact on
my use of routable addresses, and seeing that there is the potential for
the IPv4LL specs to have an impact on the use of DHCP for address
assignment, we need to be very careful that anything we do here doesn't
cause additional problems with the use of routable addresses.

- Ralph

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From: "John C. Welch" <[email-masked]>
Date: Thu, 13 Mar 2003 08:20:18 -0500

> cause additional problems with the use of routable addresses.

Because why? Stuart pointed out, and quite correctly, that IPv4LL has been
around for years, and the internet hasn't melted down. What, the internet
suddenly got fragile?

john

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From: Ralph Droms <[email-masked]>
Date: Thu, 13 Mar 2003 08:59:27 -0500

The impact I'm talking about is on the unannounced use of IPv4LL
addresses by my laptop, which causes loss of network connectivity
with no associated indication of why connectivity has been lost.

The Internet hasn't melted down, but *I've* come damn close to melting
down several times after wasting time trying to diagnose and fix the
problem.  The requirement to look at the device's assigned IP address
and then deduce that it is an IPv4LL address because I remember the
prefix for IPv4LL addresses or because I click a "More Info" button
and happen to see the "Auto-Configuration Active" box checked is
unacceptable.

Although, as Stuart said, this problem is an interface problem and
not a protocol problem, either way it is an implementation problem
that negatively impacts my usual use of routable addresses.

- Ralph

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From: "John C. Welch" <[email-masked]>
Date: Thu, 13 Mar 2003 09:52:38 -0500

> with no associated indication of why connectivity has been lost.

What OS are you running? OS X ties it's config to a configured address if
one exists.

> and happen to see the "Auto-Configuration Active" box checked is

That's a vendor implementation bug, not a v4LL bug. They're not implementing
LL correctly, and it sounds like they aren't handling single-link
multihoming even *close* to correctly. No standard can make up for a
lazy/poor implementation(NFS anyone? FTP?). That requires the people with
the checkbooks to scream.

john

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From: Ralph Droms <[email-masked]>
Date: Thu, 13 Mar 2003 10:06:14 -0500

John - did you read all of my message (you didn't quote it all).  I 
explicitly wrote:

I know I'm referring to an interface problem; I've said so
at least three times now.  Regardless, it's still an implementation
problem and it has had a negative impact on my use of the network.

I've experienced this interface problem behavior with Windows 95
(if I remember correctly), Windows 98 and Windows 2000.  I believe
Stuart said it's also a problem in some flavors of MacOS.

- Ralph

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From: "John C. Welch" <[email-masked]>
Date: Thu, 13 Mar 2003 11:16:29 -0500

> Stuart said it's also a problem in some flavors of MacOS.

Right. But it's how LL is implemented on those systems, not LL itself that
is causing the problem. Implementation is a vendor, not a standards problem.
It's not the LL address that's making your day suck, it's how the OS is
implementing LL.

We can't force implementations, unless you want a standard that is longer
than every other standard combined.

john