[dhcwg] <draft-ietf-dhc-agent-subnet-selection-03.txt> - Classfull ?

Van Aken Dirk <VanAkenD@thmulti.com> Tue, 08 October 2002 20:59 UTC

Received: from www1.ietf.org (ietf.org [132.151.1.19] (may be forged)) by ietf.org (8.9.1a/8.9.1a) with ESMTP id QAA00722 for <dhcwg-archive@odin.ietf.org>; Tue, 8 Oct 2002 16:59:02 -0400 (EDT)
Received: (from mailnull@localhost) by www1.ietf.org (8.11.6/8.11.6) id g98L0gE30615 for dhcwg-archive@odin.ietf.org; Tue, 8 Oct 2002 17:00:42 -0400
Received: from ietf.org (odin.ietf.org [132.151.1.176]) by www1.ietf.org (8.11.6/8.11.6) with ESMTP id g98L0fv30612 for <dhcwg-web-archive@optimus.ietf.org>; Tue, 8 Oct 2002 17:00:41 -0400
Received: from www1.ietf.org (ietf-mx.ietf.org [132.151.6.1]) by ietf.org (8.9.1a/8.9.1a) with ESMTP id QAA00654 for <dhcwg-web-archive@ietf.org>; Tue, 8 Oct 2002 16:58:31 -0400 (EDT)
Received: from www1.ietf.org (localhost.localdomain [127.0.0.1]) by www1.ietf.org (8.11.6/8.11.6) with ESMTP id g98Kw5v30172; Tue, 8 Oct 2002 16:58:05 -0400
Received: from ietf.org (odin.ietf.org [132.151.1.176]) by www1.ietf.org (8.11.6/8.11.6) with ESMTP id g978Elv03835 for <dhcwg@optimus.ietf.org>; Mon, 7 Oct 2002 04:14:47 -0400
Received: from ns1.thmulti.com (ietf-mx.ietf.org [132.151.6.1]) by ietf.org (8.9.1a/8.9.1a) with ESMTP id EAA10298 for <dhcwg@ietf.org>; Mon, 7 Oct 2002 04:12:27 -0400 (EDT)
Received: from smtprelay2.thmulti.com (smtprelay2 [141.11.195.242]) by ns1.thmulti.com (8.9.3/8.9.1) with ESMTP id KAA26268 for <dhcwg@ietf.org>; Mon, 7 Oct 2002 10:14:26 +0200 (MET DST)
Received: from parexch3.paris.thmulti.com (localhost [127.0.0.1]) by smtprelay2.thmulti.com (8.9.3/8.9.1) with ESMTP id KAA29749 for <dhcwg@ietf.org>; Mon, 7 Oct 2002 10:14:25 +0200 (MET DST)
Received: by parexch3 with Internet Mail Service (5.5.2653.19) id <SYZH5SGG>; Mon, 7 Oct 2002 10:14:24 +0200
Message-ID: <421CB3B9B2D2F645B548D213C0A90E55090E33@edgmsmsg01.eu.thmulti.com>
From: Van Aken Dirk <VanAkenD@thmulti.com>
To: "'dhcwg@ietf.org'" <dhcwg@ietf.org>
Cc: Dedecker Hans <DedeckerH@thmulti.com>, Dekeyser Miek <DekeyserM@thmulti.com>
Date: Mon, 7 Oct 2002 10:14:18 +0200
MIME-Version: 1.0
X-Mailer: Internet Mail Service (5.5.2653.19)
Content-Type: text/plain; charset="ISO-8859-1"
Subject: [dhcwg] <draft-ietf-dhc-agent-subnet-selection-03.txt> - Classfull ?
Sender: dhcwg-admin@ietf.org
Errors-To: dhcwg-admin@ietf.org
X-BeenThere: dhcwg@ietf.org
X-Mailman-Version: 2.0.12
Precedence: bulk
List-Unsubscribe: <https://www1.ietf.org/mailman/listinfo/dhcwg>, <mailto:dhcwg-request@ietf.org?subject=unsubscribe>
List-Id: <dhcwg.ietf.org>
List-Post: <mailto:dhcwg@ietf.org>
List-Help: <mailto:dhcwg-request@ietf.org?subject=help>
List-Subscribe: <https://www1.ietf.org/mailman/listinfo/dhcwg>, <mailto:dhcwg-request@ietf.org?subject=subscribe>

Hello Working group,


Could it be that the "Link Selection sub-option for the Relay Agent
Information Option" is a classfull option ?
i.e. According this draft, the format of the sub-option is:

>>>>
           SubOpt   Len     subnet IP address
          +------+------+------+------+------+------+
          | TBD  |   4  |  a1  |  a2  |  a3  |  a4  |
          +------+------+------+------+------+------+

The sub-option contains a single IP address that is an address con-
tained in a subnet. The value for the subnet address is determined by
taking any IP address on the subnet and ANDing that address with the
subnet mask (i.e.: the network and subnet bits are left alone and the
remaining (address) bits are set to zero).
>>>>

If I understand the above text correctly, a single (masked) IP address is
added to this sub-option by the relay agent and submitted to the DHCP
server.
The latter will subsequently supply an address within the same subnet.

I wonder though how the DHCP server can derive a subnet from a single
quantity being an IP address. e.g. 20.0.0.0 can be an alias for 20.0.0.0/8
or 20.0.0.0/29.
So my guess is that the only way the DHCP server can derive the subnet form
is based on the leading bits of the address being either class A, B or C.

Am I correct ?

Thanks in advance - Dirk


Dirk Van Aken                              THOMSON multimedia Broadband
Belgium NV
System Architect                           Prins Boudewijnlaan 47,
Tel. : 03/443.65.08                        2650 Edegem
Fax.: 03/443.66.32                         Belgium
vanakend@thmulti.com


_______________________________________________
dhcwg mailing list
dhcwg@ietf.org
https://www1.ietf.org/mailman/listinfo/dhcwg