Subject: 6lowpan DHCPv6 investigation

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Mon, 22 Mar 2010 18:14:29 -0500

6lowpan folks,

It is well-known by now that you needed to modify ND (RFC 4861)  for
your network.  Now that you are looking into DHCPv6 for address
acquisition and obtaining other parameters, here is some feedback on the
DHCPv6 front.  I hear that you network has dispensed with DAD as
specified by RFC 4862.   So if you use DHCPv6, please beware of RFC 4862
that mandates performing DAD on the DHCPv6 acquired address.   See
section 5.4 of RFC 4862 and this text from the document.

[Duplicate Address Detection MUST be performed on all unicast

addresses prior to assigning them to an interface, regardless of

whether they are obtained through stateless autoconfiguration, DHCPv6,
or manual configuration,]

However, good news for you is that RFC 4862 is flexible in that if a
link-specific document mandates the DupAddrDetectTransmitsvariable to be
zero, the NS(DAD) can be dispense with if DHCPv6 is used.   If a
link-type document hasn't be authored yet for 6lowpan, please write it
or augment an existing document with this information - maybe you
already have such info in an existing 6lowpan document.  

One other point is that if you plan to use stateless DHCPv6 in your
deployment, please do not plan on using prefix delegation (RFC 3633) in
your network because prefix delegation is only supported over stateful
DHCPv6.   Please forward this email to your mailer.

Thanks,

Hemant

Hemant Singh
Technical Leader.engineering
Product Development
[email-masked]
Phone: +1 978 936 1622
Cisco Systems, Inc.
United States
Cisco.com - http://www.cisco.com

For corporate legal information go to:
http://www.cisco.com/web/about/doing_business/legal/cri/index.html

---

From: Samita Chakrabarti <[email-masked]>
Date: Wed, 24 Mar 2010 18:19:34 -0700

Hi Hemant,

Your point on DAD relaxation in rfc 4862 has been noted by the authors
of nd drafts.

Also, nd-simple provides a mechanism for a 6LoWPAN-wide prefix delegation/relay.

Thanks for your input.
-Samita

On Mon, Mar 22, 2010 at 4:14 PM, Hemant Singh (shemant)
<[email-masked]> wrote:
> 6lowpan folks,
>
>
>
> It is well-known by now that you needed to modify ND (RFC 4861)  for your
> network.  Now that you are looking into DHCPv6 for address acquisition and
> obtaining other parameters, here is some feedback on the DHCPv6 front.  I
> hear that you network has dispensed with DAD as specified by RFC 4862.   So
> if you use DHCPv6, please beware of RFC 4862 that mandates performing DAD on
> the DHCPv6 acquired address.   See section 5.4 of RFC 4862 and this text
> from the document.
>
>
>
> whether they are obtained through stateless autoconfiguration, DHCPv6, or
> manual configuration,]
>
>
>
> zero, the NS(DAD) can be dispense with if DHCPv6 is used.   If a link-type
> document hasn’t be authored yet for 6lowpan, please write it or augment an
> existing document with this information – maybe you already have such info
> in an existing 6lowpan document.
>
>
>
> deployment, please do not plan on using prefix delegation (RFC 3633) in your
> network because prefix delegation is only supported over stateful DHCPv6.
> Please forward this email to your mailer.
>
>
>
> Thanks,
>
>
>
> Hemant
>
> Hemant Singh
> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> [email-masked]
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------
>
>

---

From: Jonathan Hui <[email-masked]>
Date: Thu, 25 Mar 2010 00:43:20 -0700

Hi Hemant,

On Mar 22, 2010, at 4:14 PM, Hemant Singh (shemant) wrote:

> acquisition and obtaining other parameters, here is some feedback on  
> the DHCPv6 front.  I hear that you network has dispensed with DAD as  
> specified by RFC 4862.   So if you use DHCPv6, please beware of RFC  
> 4862 that mandates performing DAD on the DHCPv6 acquired address.    
> See section 5.4 of RFC 4862 and this text from the document.
>
> whether they are obtained through stateless autoconfiguration,  
> DHCPv6, or manual configuration,]
>
> link-specific document mandates the DupAddrDetectTransmitsvariable  
> to be zero, the NS(DAD) can be dispense with if DHCPv6 is used.   If  
> a link-type document hasn’t be authored yet for 6lowpan, please  
> write it or augment an existing document with this information –  
> maybe you already have such info in an existing 6lowpan document.

RFC 4862 also seems to say that disabling DAD can also be an  
administrative function...

"To accommodate sites that believe the overhead of performing  
Duplicate Address Detection outweighs its benefits, the use of  
Duplicate Address Detection can be disabled through the administrative  
setting of a per-interface configuration flag."

> deployment, please do not plan on using prefix delegation (RFC 3633)  
> in your network because prefix delegation is only supported over  
> stateful DHCPv6.   Please forward this email to your mailer.

For stateful DHCPv6, there hasn't been any discussion to use DHCPv6-PD  
within a 6LoWPAN network - just the possibility of using DHCPv6 to  
assign addresses and use relay agents to support topologies where the  
server is not on-link.  For stateless DHCPv6, only configuration  
information you'd typically obtain through such a service.

--
Jonathan Hui