Subject: LL16 Split references

From: Stuart Cheshire <[email-masked]>
Date: Tue, 11 Feb 2003 19:33:36 -0800

Keith Moore wrote:

>If DHCP ends up being required (as I believe it should) then RFC 2131
>becomes a normative reference.

I hinted last week about devices that use IPv4LL for communication 
between components inside a single computer chassis.

This week Apple publicly announced the first of these devices.

<http://www.apple.com/xserve/raid/>

Xserve RAID includes hot-swappable modules. These modules have to 
communicate internally. How do they communicate? Via PCI? No. they 
communicate via Ethernet, using IPv4LL addresses.

If you think that Apple did this as a publicity stunt for the sake of 
promoting IPv4LL, let me correct that misunderstanding. The hardware 
teams at Apple are driven my making the best hardware at the lowest 
price. If a technology doesn't make sense, they're certainly not going to 
put it in just to please me.

The hardware team chose IPv4LL/Ethernet for the internal communication 
bus for a good reason. The part they were using included an Ethernet port 
on the same silicon. When they were considering what internal 
communication technology to put in the design, someone (not me) pointed 
out this spare Ethernet port that they were not planning to use. With a 
little bit of software, they got their internal communication bus for 
free, instead of having to add some other interconnect to the circuit 
board.

Now, getting back to LL16, it makes no sense to mandate that these RAID 
controller modules MUST implement a DHCP client, when they are on a 
19-inch Ethernet network, inside a single computer chassis, and we *know* 
it will never have a DHCP server on it.

Stuart

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From: Keith Moore <[email-masked]>
Date: Tue, 11 Feb 2003 23:33:26 -0500

these devices don't have to claim conformance to an IETF standard.
neither should IETF be expected to endorse Apple's products.

I am strongly opposed to permitting LL-only devices to claim conformance
to the standard.  this is completely unacceptable.

Keith

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From: Alex Karahalios <[email-masked]>
Date: Tue, 11 Feb 2003 21:43:50 -0700

In case anyone is keeping count, I am in favor of permitting LL-only 
devices. I think this is completely acceptable.

Alex Karahalios

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From: "John C. Welch" <[email-masked]>
Date: Wed, 12 Feb 2003 08:04:45 -0500

> devices. I think this is completely acceptable.

Especially with Stuart's example. Anytime you have a need for easy setup
within a limited scope, (intra cluster communication on a dedicated channel
comes to mind), LL4 is perfect.

john

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

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From: Keith Moore <[email-masked]>
Date: Wed, 12 Feb 2003 09:48:31 -0500

> comes to mind), LL4 is perfect.

this is out of scope for IETF, and out of scope for this working group.

---

From: Robert Elz <[email-masked]>
Date: Thu, 13 Feb 2003 17:05:55 +0700

Date:        Tue, 11 Feb 2003 19:33:36 -0800
    From:        Stuart Cheshire <[email-masked]>
    Message-ID:  <[email-masked]>

I can't imagine what this has to do with LL16, but ...

  | I hinted last week about devices that use IPv4LL for communication 
  | between components inside a single computer chassis.
  | 
  | This week Apple publicly announced the first of these devices.
  | 
  | <http://www.apple.com/xserve/raid/>

I think you're not understanding the reason for MUSTs etc in RFCs.

  | Xserve RAID includes hot-swappable modules. These modules have to 
  | communicate internally. How do they communicate? Via PCI? No. they 
  | communicate via Ethernet, using IPv4LL addresses.

I've had a quick(ish) look at that web page, and PDF files of specs available
from it, and I can't find a thing about IP, or Link Local addresses.

I'm not trying to say you're making this up - of course not.   What I am
saying is that there's no reason for Apple to mention any of the internal
details of how their device operates.

For the same reason, there's no reason for them to claim they conform, or
even actually conform, with any of the IETF's (or anyone else's) standards.

You justify the use of ethernet for communications in your message, and
that's fine (not that I care anyway, what would matter to me would be
whether the device performs adequately, not what kind of wiring is installed).

But for all anyone can tell, not that anyone would care, even if we know
you're using ethernet, you could just as well be using Ethertalk, rather
than IP, and the device would appear identical.

I have no doubt there are reasons for the choice of IP, but none of them
are going to be relevant to us - that's all internal Apple engineering
decisions.

Even given that Apple have decided to use IP, there's no particular reason
they should be using 169.254 - even if the desire is to do random addresses
(ie: no configuration) the device would work just the same if it used network
10, or 172.16 or 192.168.1 or something, wouldn't it?

There's no way anyone from outside can ever see, no reason for anyone outside
to ever care, and no reason (aside from your attempts to argue here) for
Apple to even ever tell anyone what they're doing in this area.

The purpose of open standards (like the IETFs) is so that people can say
"we do it the way the standard specifies", so that others can know that if
they select the device in question, it will (or should) interoperate
correctly with other devices that they want it to interoperate with.

If that is irrelevant to some particular purpose, anyone is free to take
any IETF standard, and bend, mutilate, and spindle it to meet their own
needs - that is, to take some of the ideas, and make use of them in other
ways that are anything from close to, to completely different from the
intent of the IETF standard.   They can ignore MUST and MUST NOT however
much suits them, as they're never going to be claiming that they're actually
supporting the standard - they're just taking the ideas.

Ignoring the lineage of the LL address stuff, that's what Apple are
apparently doing here.   No-one is going to stop them, no-one is going
to care which parts of the spec they are using, and which parts they're
ignoring.   That is, nothing about what the IETF says need have any
effect whatever on how this particular device (or others that might
be similar, from the same or other sources) works - in some cases the
IETF spec might contain some ideas and rules from the experience of
the people writing it, which might be worth noting, or being aware of,
but nothing in an IETF spec is ever mandatory for anyone.   You just
don't get to claim to conform to the spec if you don't (that would
be fraud, or misleading advertising, and could cause trouble).   Here
no-one is claiming anything about LL address usage - so even if the
spec does end up requiring DHCP clients in all LL nodes, there's no
reason for Apple to take any notice of that, all they need to do is
convince themselves that it will never be useful.

kre