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Re: question about DHCPv6 prefix delegation usage



Laurent - assuming you want aggregation for routing, the ISP DHCPv6 server
would have to be configured to recognize that A and B are downstream from
the CPE, and therefor should be assigned /64s that somehow aggregate under
the /48 assigned to the CPE.

Pushing the responsibility to a DHCPv6 server in the CPE allows the CPE to
assign prefixes from its /48 to the links between A and B, and other
prefixes to the DHCPv6 server for delegation to A and B.

In the picture below, the CPE would be reponsible for assigning a /64 from
its /48 to the links between the CPE and A and B.  A and B would request
prefix(es) for their downstream links.  A might request a /64 if it has only
one downstream link, or a shorter prefix if it has more than one downstream
link.

A and B could be part of the same organization as the CPE, or part of
different organizations.  It's not clear whether a link between A and B
would be useful or sensible.

If ythere is a link between A and B, there's an issue about
whether A or B (or both?) should assign a prefix to that link.

- Ralph


At 10:52 AM 6/2/2004 +0200, Laurent.Clevy@alcatel.fr wrote:

>Thank you Tony and Christian for your answers.
>
>In my question, I missed the point that the ISP and CPE are in different 
>domain,
>so the distribution of the /48 to the CPE is supposed to follow a 
>different policy
>than how the /64 are distributed.
>And having 2 levels of DHCPv6 PD servers is scalable.
>
>Yes, of course A and B are DHCPv6 clients, and the CPE (in my initial 
>question) was supposed to be a working DHCP relay.
>
>
>I have other questions based on the same (theorical) network:
>
>             ISP (ISP DHCPv6 PD server, gives /48 to the CPE)
>              |
>              |
>             CPE  (Customer DHCPv6 PD server, gives /64 prefixes)
>             / \
>            /   \
>        ---B----A---
>           |    |
>
>
>How many /64 prefixes A and B are supposed to request (to the CPE),
>and for what usage ?  Only for connectivity with the CPE ?
>
>Does the link between A and B have any sense
>or are A and B part of different clients / organisations ?
>
>Is there any (private?) network connected to A and B ?
>
>
>=> In others words, what kind of networks/links are supposed to be 
>connected this CPE when using DHCPv6 PD ?
>
>And now the CPE is a DHCPv6 PD server, it should be able to delegate not 
>only /64 prefixes, right ?
>
>Regards,
>
>Laurent
>
>
>Tony Hain wrote:
>
>>You are asking a question which mixes technology with policy. The simple
>>answer to your question is YES. The complex answer is a function of the
>>policy at the ISP DHCP server. Will it accept requests from A & B? Are you
>>expecting the set of /64's allocated to A & B to be contained within the /48
>>at the CPE? If so what mechanism enforces that at the DHCP server? (IE: how
>>does the DHCP server associate A or B with the CPE?)
>>What is the point of such a broken deployment model? If the expectation is
>>to allocate a /48 to the CPE using DHCP-PD (which it should be), then put a
>>DHCP server in the CPE and have it delegate /64's from that space. This
>>ensures that A & B get their space from the appropriate point in the
>>hierarchy, as well as distributes the load. Consider that it will not be
>>long before A & B have expanded to ~10^3 devices behind that CPE, multiple
>>the number of CPE by that and figure out how to scale the authentication &
>>association logic for a central DHCP server to ensure everything works as
>>expected. Then reconsider the simplicity of distributing that function to
>>the CPE.
>>
>>Tony
>>
>>
>>
>>
>>>-----Original Message-----
>>>From: ipv6-bounces@ietf.org [mailto:ipv6-bounces@ietf.org] On Behalf Of
>>>Laurent.Clevy@alcatel.fr
>>>Sent: Tuesday, June 01, 2004 7:12 AM
>>>To: ipv6@ietf.org; Ralph Droms
>>>Subject: question about DHCPv6 prefix delegation
>>>
>>>Hi All,
>>>
>>>I have a question about DHCPv6 prefix delegation (RFC 3633).
>>>
>>>Given the following network:
>>>
>>>
>>>             ISP (Location of DHCPv6 server)
>>>              |
>>>              |
>>>             CPE           /48
>>>             / \
>>>            /   \
>>>        ---B----A---
>>>           |    |
>>>
>>>
>>>Is it possible to configure the DHCP server to allocate  :
>>>- a /48 prefix to the CPE node
>>>- and several /64 prefixes to the nodes A and B ?
>>>
>>>Thank you for any help,
>>>
>>>Regards,
>>>
>>>Laurent
>>>
>>>--
>>>Laurent ClÚvy
>>>Alcatel CIT, R&I             Voice: +33 (0)1 69 63 18 34
>>>Route de Nozay               Fax  : +33 (0)1 69 63 13 59
>>>91460 Marcoussis             mailto:Laurent.Clevy@alcatel.fr
>>>
>>>
>>>
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>>>
>>
>>
>>
>
>
>--
>Laurent ClÚvy
>Alcatel CIT, R&I             Voice: +33 (0)1 69 63 18 34
>Route de Nozay               Fax  : +33 (0)1 69 63 13 59
>91460 Marcoussis             mailto:Laurent.Clevy@alcatel.fr
>


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