Subject: Re: [Fwd: Re: Requirements for Service Discovery]

From: Stuart Cheshire <[email-masked]>
Date: Tue, 20 Aug 2002 18:49:34 -0700

A short question, and a long answer from Robert Elz, which I will refrain 
from repeating in its entirety here. I think this is the crux of the 
matter:

>The principle problem is not how one would manage to tell the
>primary server that the data was supposed to vanish, but how
>that server would pass along that information to secondary servers.

If I understand this correctly, Robert is saying that he believes:

(c) a garbage collection mechanism to purge old records would be nice,
    but it is simply not possible.

I would submit that the definition of "simply not possible" is merely a 
matter of where you choose to set your horizons.

If the usefulness of DNS UPDATE is fundamentally undermined by the lack 
of a garbage collection mechanism to purge old records, then we (the IETF 
community) should take on the challenge to solve that problem, not simply 
declare it impossible and give up. Just as DNS migrated from AXFR to IXFR 
over time, I see no reason it couldn't migrate from IXFR to some new 
thing ("IXFR2"?) which does provide the necessary garbage collection 
support to make DNS UPDATE a useful technology.

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

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From: Bernard Aboba <[email-masked]>
Date: Tue, 20 Aug 2002 18:38:23 -0700 (PDT)

> community) should take on the challenge to solve that problem

See:

http://www.ietf.org/internet-drafts/draft-janardhan-dnsext-aging-01.txt

---

From: Robert Elz <[email-masked]>
Date: Wed, 21 Aug 2002 13:36:55 +0700

Date:        Tue, 20 Aug 2002 18:49:34 -0700
    From:        Stuart Cheshire <[email-masked]>
    Message-ID:  <[email-masked]>

  | I would submit that the definition of "simply not possible" is merely a 
  | matter of where you choose to set your horizons.

That's true, but ...

  | If the usefulness of DNS UPDATE is fundamentally undermined by the lack 
  | of a garbage collection mechanism to purge old records,

this isn't.

DNS UPDATE works just fine as it is, there are applications that manage
it just fine, and the lack of any internal mechanism in the DNS to make
old stuff go away doesn't bother those in the least.

However, of course, a false premise doesn't imply a false conslusion, so:

  | then we (the IETF community) should take on the challenge to solve that
  | problem, not simply declare it impossible and give up.

isn't necessarily false - just nothing above on its own would drive us to
this state.

What you really mean is that you have a use for DNS update, which doesn't
work well without a cleanup mechanism.   Of course, here, we all know that
I don't think much of that proposed use...

I have no doubt but that this could be made to work, with sufficient effort.
But do remember that when dnsind was looking at this, a lot of effort was
expended in exactly that direction, with precisely zero results.

Also, note that there is a considerable swell of background feeling that
it is getting close to the time to simply scrap the DNS, and invent DNS2.
Any proposal that starts to make major changes to how the DNS functions
is going to (I suspect) get pushback both from the people who simply
don't see the need, and from the people who agree to the need, but who
don't want to bother with yet another hack to the current DNS.

But whatever your feeling on this is, this WG is most certainly not the
place to be discussing this kind of DNS change - take to to the dnsext WG
([email-masked]) where you will get a whole stack of DNS
people to comment.

kre

ps: I do know about the draft that Bernard mentioned, as best I can tell,
it is going precisely nowhere.

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From: "John C. Welch" <[email-masked]>
Date: Wed, 21 Aug 2002 10:11:31 -0400

> old stuff go away doesn't bother those in the least.

Well, it doesn't do much for the humans who have to clean up after this.

> expended in exactly that direction, with precisely zero results.

Well, then maybe it's time to look at it again. The Internet is a rather
dynamic place, and what wasn't a good idea last year doesn't guarantee that
it's a bad idea this year

> don't want to bother with yet another hack to the current DNS.

Oh great...just what we need,  moratorium on improving DNS because "The
Exciting New World of DNS2 Will Make It All Better"

Pardon my cynicism, but we need both. IPv6 hasn't yet replaced IPv4, but it
would have been foolish to not do anything to improve IPv4 while waiting for
IPv6. Get started on DNS2, but let's not sit on our hands in the meantime.

> ([email-masked]) where you will get a whole stack of DNS

Well, actually, since DNS is central to Zeroconf, yes it is, if you think
about it. Besides, it's always better to propose a change that fixes a real
world problem, as opposed to a theoretical one.

john

-- 
John C. Welch
IT Manager
MIT Police
(617) 253 - 3093 work
(508) 579 - 7380 cell
(617) 253 - 8822 fax

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From: Aidan Williams <[email-masked]>
Date: Thu, 22 Aug 2002 10:01:05 +1000

John C. Welch wrote:

[ comments about not being able to "fix" the DNS ]

> Well, actually, since DNS is central to Zeroconf,
 > yes it is, if you think about it.

As an alternative, perhaps we should be working on making "DNS"
less central to zeroconf.  It is certainly a possibility, if you
think about it.

-- 

regards
	aidan
____
:wq!

Sydney Network Research Lab             [email-masked]
Motorola Australian Research Centre          phone: +61 2 9666 0649
Locked Bag 5028, Botany NSW 1455              phax: +61 2 9666 0501
Australia                            http://marc.labs.mot.com/snrl/

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From: Robert Elz <[email-masked]>
Date: Thu, 22 Aug 2002 19:36:55 +0700

Date:        Wed, 21 Aug 2002 10:11:31 -0400
    From:        "John C. Welch" <[email-masked]>
    Message-ID:  <[email-masked]>

  | Well, it doesn't do much for the humans who have to clean up after this.

DNS Update is mostly used by DHCP servers, which manage the cleaning
up pretty well by themselves...

  | Well, then maybe it's time to look at it again. The Internet is a rather
  | dynamic place, and what wasn't a good idea last year doesn't guarantee that
  | it's a bad idea this year

Nothing was said about "bad ideas", what was said was that a suitable
method to make it work hadn't been found.   By all means, go ahead and
propose a solution to the problem.   If it works, lots of people will be
very happy.   Just don't expect people who already spend a lot of time
on this to do it for you - nor for them to be very sympathetic to ideas
that won't work (propose something unworkable and expect a very brusque
response).

  | Pardon my cynicism, but we need both. IPv6 hasn't yet replaced IPv4, but it
  | would have been foolish to not do anything to improve IPv4 while waiting for
  | IPv6. Get started on DNS2, but let's not sit on our hands in the meantime.

That's fine - and incremental improvements are continually being made to
the DNS (as they are to IPv4).   But no-one rational would suggest making
a sweeping change that would involve upgrading everyone's IPv4 stack at
this stage of the game.   Improvements to the DNS will happen, and do
happen - major changes are starting to look less likely (but who can tell).

kre

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From: Keith Moore <[email-masked]>
Date: Tue, 27 Aug 2002 16:34:44 -0400

>     but it is simply not possible.

(c') DNS wasn't designed to do this, and it's very difficult to retro-fit 
it into DNS in a way that allows incremental upgrading of DNS servers.

Keith