Subject: Re: [ntpwg] draft-ietf-ntp-dhcpv6-ntp-opt-00 is now a WG item

From: "Benoit Lourdelet (blourdel)" <[email-masked]>
Date: Wed, 11 Jun 2008 12:08:43 +0200

Hello,

As authors, we received the following comments from Alfred Hines with
request to publish it on his behalf :

"(1)  Layering / Semantic Overloading

Sections 3 and 4 indicate that the NTP Server Address Suboption can be
"used" to carry an IPv6 multicast group address.

This semantical overloading seems to be an unfortunate 'hack' or
*abuse* of the option.  Usually, this option carries the *source*
address of NTP inbound packets; in the multicast case that's the
*destination* address of inbound NTP packets to listen for.

You have provided for a 16-bit suboption type namespace.
This should easily accommodate the allocation of another code point for
a specific NTP_SUBOPTION_MC_ADDR .

Thus, decision making logic in DHCPv6 clients could be based on the
suboption type and would not have to have built-in knowledge of which
IPv6 addresses are multicast addresses.
(This conceivably even could change with a future update of the IPv6
address allocation policy/architecture!)

Leaving the knowledge of what comprises feasible IPv6 multicast
addresses in the multicast modules of an IPv6 implementation (and only
dealing *there* with the subtle issues related to MC scope in IPv6)
would IMHO be a much clearer layering decision.
"

Here our view on that comment :

We think the remark about semantic overloading is perfectly valid. We
plan to make the change according to your suggestions in the next
version. 

Regards

Richard Gayraud and Benoit Lourdelet 

-----Original Message-----
From: Benoit Lourdelet (blourdel) 
Sent: Friday, May 30, 2008 1:41 PM
To: [email-masked]; [email-masked]
Cc: Richard Gayraud (rgayraud); Benoit Lourdelet (blourdel)
Subject: draft-ietf-ntp-dhcpv6-ntp-opt-00 is now a WG item

Hello,

The Network Time Protocol (NTP) Server Option for DHCPv6 is now a WG
item.
http://www.ietf.org/internet-drafts/draft-ietf-ntp-dhcpv6-ntp-opt-00.txt

Please comment on this revision that includes the comments received on
the personal submission versions  of the draft.

regards

Richard Gayraud, Benoit Lourdelet

A new version of I-D, draft-ietf-ntp-dhcpv6-ntp-opt-00.txt has been
successfuly submitted by Benoit Lourdelet and posted to the IETF
repository.

Filename: draft-ietf-ntp-dhcpv6-ntp-opt

Revision: 00

Title: Network Time Protocol (NTP) Server Option for DHCPv6

Creation_date: 2008-05-14

WG ID: ntp

Number_of_pages: 10

Abstract:

The NTP Server Option for DHCPv6 provides NTP (Network Time Protocol
version 4) configuration information to DHCPv6 hosts.

The IETF Secretariat.

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