Subject: DHCPv6 address used when M or O bit is set

From: Dominik Elsbroek <[email-masked]>
Date: Wed, 4 Apr 2012 15:55:03 +0200

Hi all,

the discussion on the mailing list titled "RA "requires" DHCPv6 ?" is
quite confusingto me since RFC 4862 states, the flags M and O are
removed, but not deprecated. They don't even longer exist, but still
exist?

But what should a client do now? Is a client asked to request further
information from a DHCPv6 server if it receives a router advertisement
with these bits set? And if, which address should the client use? The
link local FF02:0:0:0:0:0:1:2 (All-dhcp-agents) or the site-local
FF05:0:0:0:0:0:1:3 (All-dhcp-servers)?

Kind regards,
Dominik

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From: Fernando Gont <[email-masked]>
Date: Wed, 04 Apr 2012 16:12:14 +0200

Hi, Dominik,

On 04/04/2012 03:55 PM, Dominik Elsbroek wrote:
> removed, but not deprecated. 

What's removed is the corresponding text, not the bits. See page 19 of
RFC 4861: the bits are still there.

> They don't even longer exist, but still
> exist?

I'm curious about why the corresponding text was removed. In particular
when at the time (2007) the DNS options was not yet widely implemented,
and hence you *needed* DHCPv6 to learn the addresses of recursive DNS
servers dynamically.

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: [email-masked]
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492

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From: Dominik Elsbroek <[email-masked]>
Date: Wed, 4 Apr 2012 16:38:45 +0200

Hi Fernando,

> RFC 4861: the bits are still there.

In RFC4862, Appendix C there is one point:

Removed the text regarding the M and O flags, considering the
      maturity of implementations and operational experiences.
      ManagedFlag and OtherConfigFlag were removed accordingly.  (Note
      that this change does not mean the use of these flags is
      deprecated.)

Not sure how to interprete this. Perhapts I am just missing a link,
but M and O flag in RFC 4861 doesn't tell how to do SLAAC, e.g. when
the nameserver should be determined by DHCPv6-server.

> and hence you *needed* DHCPv6 to learn the addresses of recursive DNS

I am still very curious which address a client should use, if the O or
M flag is set, to find a DHCPv6 server.

Cheers,
Dominik

---

From: "Duncan, Jeremy" <[email-masked]>
Date: Wed, 4 Apr 2012 07:50:05 -0700

---I am still very curious which address a client should use, if the O or
M flag is set, to find a DHCPv6 server.

The server listens on ff02::1:2 and/or ff02::1:3

010100110110010101101101011100000110010101110010001000000100011001101001

Jeremy Duncan
Senior Director, IPv6 Network Architect Salient Federal Solutions, Inc.
(Now including SGIS & Command Information Inc.)
4000 Legato Road, Suite 600 Fairfax, VA 22033
Google Voice:  540.440.1193
[email-masked]

________________________________________

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From: Bob Hinden <[email-masked]>
Date: Wed, 4 Apr 2012 08:08:44 -0700

Dominik,

The M and O flags are defined in RFC4861.  They are not removed (or deprecated).

Bob

On Apr 4, 2012, at 6:55 AM, Dominik Elsbroek wrote:

> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> [email-masked]
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------

---

From: Suresh Krishnan <[email-masked]>
Date: Wed, 4 Apr 2012 11:51:33 -0400

Hi Jeremy,
  The DHCPv6 client on a host will use its link-local address as the
source address and ff02::1:2 as the destination address.

Cheers
Suresh

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From: JINMEI Tatuya / 神明達哉 <[email-masked]>
Date: Wed, 04 Apr 2012 13:52:57 -0700

At Wed, 4 Apr 2012 16:38:45 +0200,

> the nameserver should be determined by DHCPv6-server.

As clearly noted, "removed" doesn't mean these flags were deprecated
in the protocol.  They were simply removed from the RFC4862 text as an
out-of-scope item for that particular RFC (and the assumption was they
should be standardized in other documents).

---
JINMEI, Tatuya
Internet Systems Consortium, Inc.

---

From: Karl Auer <[email-masked]>
Date: Thu, 05 Apr 2012 08:41:38 +1000

> and hence you *needed* DHCPv6 to learn the addresses of recursive DNS

Me too!

The RFC4862 says

   "Removed the text regarding the M and O flags, considering the
    maturity of implementations and operational experiences.
    ManagedFlag and OtherConfigFlag were removed accordingly. (Note
    that this change does not mean the use of these flags is
    deprecated.)"

The only way I can interpret this is "people are doing whatever the hell
they like with these flags, and some of those implementations are pretty
well-established, so we are not going to try to define how the flags
should be used because no matter what we say, it will conflict with the
way someone out there is doing things. However, people should definitely
still use these flags! We aren't taking them away, we're just refusing
to define how they should be used."

It seems a strange thing to say, so maybe my interpretation is wrong :-)

Regards, K.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Karl Auer ([email-masked])
http://www.biplane.com.au/kauer

GPG fingerprint: AE1D 4868 6420 AD9A A698 5251 1699 7B78 4EEE 6017
Old fingerprint: DA41 51B1 1481 16E1 F7E2 B2E9 3007 14ED 5736 F687

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From: "Manfredi, Albert E" <[email-masked]>
Date: Wed, 4 Apr 2012 17:58:27 -0500

Can we vote to have your interpretation pasted into RFC 4862bis?

Honestly, that I get, at least.

Bert

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Karl Auer
Sent: Wednesday, April 04, 2012 6:42 PM
To: [email-masked]
Subject: Re: DHCPv6 address used when M or O bit is set

Me too!

The RFC4862 says

Regards, K.