Re: [dhcwg] dhcwg Digest, DHCP Renew vs Confirm

>          I asked Ole about this at V6 World Congress last week, and he
mentioned that it wasn't in RFC 3633 because Confirm is for detecting
on-link confirmation.   It's possible I misunderstood him, if so he can
feel free to jump in.

   Any responding servers will indicate whether those

   addresses are appropriate for the link to which the client is

   attached with the status in the Reply message it returns to the

   client.

...

   NotOnLink       4 The prefix for the address is not appropriate for

                     the link to which the client is attached.

I disagree as the RFC 3315 text never says "on-link" in the strict sense
of what "on-link" means for IPv6. It says "appropriate for the link".
The status code is "NotOnLink" but that is something that is definitive
in the case when a delegate prefix is not 'appropriate' for the link. I
believe Ralph was purposely careful in the language used in RFC 3315
that we didn't imply that an address was "on-link" in the sense of the L
bit for ND.

I don't remember the timing of the documents and work on RFC 3633 might
have started before RFC 3315 was finalized and perhaps an earlier 3315
draft had some different terminology which was more directly tied to
"on-link". (Given that the RFC publication dates are only 6 months
apart, I suspect they were worked on in parallel. While the IETF process
was faster back then, it was never that fast.)

>          Is a DHCP Client not following RFC 3315 if they don't
transmit a DHCP Confirm message? 

   In any situation when a client may have moved to a new link, the

   client MUST initiate a Confirm/Reply message exchange.  

Thus, a strict read of RFC 3315 says it is required (MUST - not SHOULD).

Perhaps the above are items for -bis documents if they are ever done.
Or, a new draft might want to propose a reconsidering of these issues?

-          Bernie

From: Timothy Winters [mailto:twinters@iol.unh.edu] 
Sent: Wednesday, February 15, 2012 11:53 PM
To: Bernie Volz (volz)
Cc: Huan Huan; dhcwg@ietf.org
Subject: Re: [dhcwg] dhcwg Digest, DHCP Renew vs Confirm

Hi Bernie,

            I asked Ole about this at V6 World Congress last week, and
he mentioned that it wasn't in RFC 3633 because Confirm is for detecting
on-link confirmation.   It's possible I misunderstood him, if so he can
feel free to jump in.

            As you point out RFC 3315 doesn't prevent an implementation
from transmitting a Renew message when this happens.   So they are
within the specification for transmitting the Renew message.  The
missing piece is that we have DHCP clients, in this case CE Routers,
that don't transmit Confirm messages. RFC 3315 states a Confirm message
should happen when a device may have moved to another link, so
unplugging the physical link should cause a DHCP Confirm message when
plugged back in.  

            Is a DHCP Client not following RFC 3315 if they don't
transmit a DHCP Confirm message? 

Regards,

Tim

On Feb 15, 2012, at 10:29 PM, Bernie Volz (volz) wrote:

I don't really see what's wrong with EITHER a REBIND or CONFIRM (or even
both, one for IA_PD and one for address). Not really sure why RFC 3633
didn't permit a Confirm.

However, if one does a strict read of the standards, the two (Confirm
for address, Renew for PD) is what a  client SHOULD do.

But, there's no reason a prefix can't be confirmed just as easily as an
address.

Perhaps Ole had a reason for this in RFC 3633, but alas it is not
documented (at least that I could see).

And, a Rebind (for an address) at any time isn't really "wrong".

For a compliance test, you are probably forced to follow the standards
as that is the only thing that you can assure (a server may be strict in
following RFC 3633 and consider a Confirm with prefixes "wrong"). (Cisco
Network Registrar will deal with all of the possibilities.)

-          Bernie

From: dhcwg-bounces@ietf.org [mailto:dhcwg-bounces@ietf.org] On Behalf
Of Huan Huan
Sent: Wednesday, February 15, 2012 8:56 PM
To: Timothy Winters
Cc: dhcwg@ietf.org
Subject: Re: [dhcwg] dhcwg Digest, DHCP Renew vs Confirm

I don't think so.

2012/2/15 Timothy Winters <twinters@iol.unh.edu>

Hi Huan,

      Is it ok to transmit just a Renew message containing both the
IA_NA and IA_PD when the link goes down?

Regards,

Tim

On Feb 14, 2012, at 8:12 PM, Huan Huan <shawngespan@gmail.com> wrote:

	Hi Tim,

	I think CE Router may transmit Confirm msg containing the
assigned IA_NA and Renew msg containing the assigned IA_PD separately.

	BR,

	Huan 

	2012/2/15 <dhcwg-request@ietf.org>

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	Today's Topics:

	  1. I-D Action: draft-ietf-dhc-forcerenew-nonce-04.txt
	     (internet-drafts@ietf.org)
	  2. DHCP Renew vs Confirm (Timothy Winters)

----------------------------------------------------------------------

	Message: 1
	Date: Tue, 14 Feb 2012 02:40:41 -0800
	From: internet-drafts@ietf.org
	To: i-d-announce@ietf.org
	Cc: dhcwg@ietf.org
	Subject: [dhcwg] I-D Action:
draft-ietf-dhc-forcerenew-nonce-04.txt
	Message-ID:
<20120214104041.23040.30559.idtracker@ietfa.amsl.com>
	Content-Type: text/plain; charset="utf-8"

	A New Internet-Draft is available from the on-line
Internet-Drafts directories. This draft is a work item of the Dynamic
Host Configuration Working Group of the IETF.

	       Title           : Forcerenew Nonce Authentication
	       Author(s)       : David Miles
	                         Wojciech Dec
	                         James Bristow
	                         Roberta Maglione
	       Filename        : draft-ietf-dhc-forcerenew-nonce-04.txt
	       Pages           : 12
	       Date            : 2012-02-14

	  Dynamic Host Configuration Protocol (DHCP) FORCERENEW allows
for the
	  reconfiguration of a single host by forcing the DHCP client
into a
	  Renew state on a trigger from the DHCP server.  In Forcerenew
Nonce
	  Authentication the server sends a nonce to the client on the
initial
	  DHCP ACK that is used for subsequent validation of a
FORCERENEW
	  message.  This document updates RFC 3203.

	A URL for this Internet-Draft is:

http://www.ietf.org/internet-drafts/draft-ietf-dhc-forcerenew-nonce-04.t
xt

	Internet-Drafts are also available by anonymous FTP at:
	ftp://ftp.ietf.org/internet-drafts/

	This Internet-Draft can be retrieved at:

ftp://ftp.ietf.org/internet-drafts/draft-ietf-dhc-forcerenew-nonce-04.tx
t

	------------------------------

	Message: 2
	Date: Tue, 14 Feb 2012 08:43:50 -0500
	From: Timothy Winters <twinters@iol.unh.edu>
	To: dhcwg@ietf.org
	Subject: [dhcwg] DHCP Renew vs Confirm
	Message-ID: <C0CA95B6-1743-4D37-9BCC-D104453EBF9A@iol.unh.edu>
	Content-Type: text/plain; charset=us-ascii

	Hello,
	       While testing some CE Router implementations we have
noticed a interesting behavior that is within the specifications but not
clearly documented.  I wanted to get the working group thoughts on this.

	       Currently when a CE Router acting as a DHCP client,
assigned both IA_NA and IA_PD, is unplugged from the network.  When
reattached to the link the DHCP client transmits a DHCP Renew containing
both the IA_NA and the IA_PD.

	       3315 Section 18.1.2 says that when link goes down a DHCP
client implementation should transmit a DHCP Confirm message containing
the assigned IA_NA.

	       3633 Section 12.1 doesn't allow the use of the Confirm
message.  It states that DHCP Renew message, containing the assigned
IA_PD, should be used when the link goes down.

	       According to the specifications a DHCP client should
retransmit DHCP Confirm and DHCP Renew when link goes up.   The behavior
we are seeing is the DHCP client transmits a DHCP renew containing both
the IA_NA and IA_PD.

	       This behavior isn't causing interoperability issues as
all the servers we have tried still respond properly to the DHCP Renew
messages.

	       Is it ok when a DHCP client loses link for it to transmit
one DHCP Renew message?

	Regards,
	Tim
	UNH-IOL

	------------------------------

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	-- 
	Huan Huan

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Huan Huan