Subject: [dhcwg] Gen-ART review of draft-ietf-v6ops-ipv6-cpe-router-06

From: Ole Troan <[email-masked]>
Date: Mon, 26 Jul 2010 13:17:47 +0200

the Gen-ART review of the "Basic Requirements for IPv6 Customer Edge Routers" resulted in some concerns regarding how DHCPv6 is used.

particularly regarding the use of address assignment and prefix delegation on the WAN-side of the CE router. please see section 4.2 and in particular requirements W-5, WAA-6, WAA-7, WPD-4, WPD-5, WPD-7.

as the authors of the document we were requested to ask the following questions to the DHC WG:

- what is the technical opinion about the DHCPv6 related requiments
of the document?
- are some questions raised by the document is the scope of the DHC WG
and should be addressed by an extra work by the DHC WG?

Best regards,
Ole

---

From: "Bernie Volz (volz)" <[email-masked]>
Date: Sat, 31 Jul 2010 21:46:07 -0500

Ole, my personal opinion is that this is fine (wrt to DHCPv6).

However, WPD-7 is technically incorrect ...

>From RFC 3315, section 17.2.2 (Advertise processing):

   If the server will not assign any addresses to any IAs in a
   subsequent Request from the client, the server MUST send an Advertise
   message to the client that includes only a Status Code option with
   code NoAddrsAvail and a status message for the user, a Server
   Identifier option with the server's DUID, and a Client Identifier
   option with the client's DUID.

And, WPD-7 reads:

   WPD-7:  If the IPv6 CE router requests both an IA_NA and an IA_PD in
           DHCPv6, it MUST accept an IA_PD in DHCPv6 Advertise/Reply
           messages, even if the message does not contain any addresses
           (IA_NA options with status code equal to NoAddrsAvail).

So, the server's Advertise response would be an IA_PD option (with an
IAPREFIX) and a Status Code option of NoAddrsAvail. There will be no
IA_NA options. At least, that's the way I would interpret this.

This is also an edge case as it depends on how literally you interpret
section 17.2.2 ... this implies that no other options are returned (such
as those from the ORO) and what about IA_PD? But, my interpretation is
that this 17.2.2 applies only if there are no IA_PD options - if there
are, the server should continue processing the request and return the
IA_PD plus any client request options (except of course if the IA_PD
fails to assign any prefixes).

The server I work on handles this and returns no IA_NA, Status Code of
NoAddrsAvail, and IA_PD for the Advertise. 

Now, another way to interpret section 17.2.2 is to change "will not
assign any addresses" to "will not assign any addresses or delegate any
prefixes", in which case the response would be a bit different ... but,
that doesn't make much sense as the NoAddrsAvail status code only
applies to addresses.

Note that for the Request, the Reply would be as written in WPD-7 as
section 18.2.1 of RFC 3315 reads:

   If the server cannot assign any addresses to an IA in the message
   from the client, the server MUST include the IA in the Reply message
   with no addresses in the IA and a Status Code option in the IA
   containing status code NoAddrsAvail.

However, in most cases the Request would likely never contain the IA_NA
because the Advertise told the client addresses are not available.

I'm not sure why the RFC 3315 behavior was designed to be different
between Solicit/Advertise and Request/Reply and how the Advertise
behavior was meant to interact with PD. 

Perhaps this is something to work out and then issue an Errata (for RFC
3315)? 

- Bernie

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Ole Troan
Sent: Monday, July 26, 2010 7:18 AM
To: Dhcwg Group
Cc: [email-masked]; Francis Dupont
Subject: [dhcwg] Gen-ART review of draft-ietf-v6ops-ipv6-cpe-router-06

the Gen-ART review of the "Basic Requirements for IPv6 Customer Edge
Routers" resulted in some concerns regarding how DHCPv6 is used.

particularly regarding the use of address assignment and prefix
delegation on the WAN-side of the CE router. please see section 4.2 and
in particular requirements W-5, WAA-6, WAA-7, WPD-4, WPD-5, WPD-7.

as the authors of the document we were requested to ask the following
questions to the DHC WG:

Best regards,
Ole
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