Subject: RE: [dhcwg] IPv6 prefix delegation extension

From: "Changming Liu" <[email-masked]>
Date: Mon, 14 Feb 2005 09:53:40 -0800

Will this make the PD more complicated, hard to implement and hard to
configure as well? Is it possible to run DHCP PD at each hop down the
tree?

Changming

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Andreas Maier
Sent: Sunday, February 13, 2005 4:49 PM
To: [email-masked]
Subject: [dhcwg] IPv6 prefix delegation extension

Dear working group members!

RFC-3633 "IPv6 Prefix Options for DHCPv6" specifies a procedure
for prefix delegation in IPv6. Although not stated explicitly
the approach seams to be limited to one level of delegation.

I think that hierarchical networks (in the sense of tree like
structures with multiple levels and routers at each tree-node)
will become very common. Prefix delegation as of RFC-3633 can
be extended to automatically configure such network architectures.

Major points to consider are subnet splitting, aggregation,
renumbering and revocation for efficient utilisation of address
resources as well as discussing very short delegation lifetimes
in case of "mobile networks".

I would like to develop an extended prefix delegation mechanism for
hierarchical IPv6 network.  Are there ongoing investigations in
this area or is it just a stupid idea?  I would very much appreciate
comments on this idea as well as references to continuative
information or research.

Thank you for your help. Best regards,
-andi

-- 
| Andreas Maier                     University of Salzburg
|
| ([email-masked])             Department of Computing Sciences
|
| Tel. +43/662/8044-6339            Jakob Haringerstr. 2
|
| Fax. +43/662/8044-611             5020 Salzburg / Austria, Europe
|

_______________________________________________
dhcwg mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/dhcwg

_______________________________________________
dhcwg mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/dhcwg

---

From: Mark Thompson <[email-masked]>
Date: Tue, 15 Feb 2005 13:04:43 +0000

> configure as well? Is it possible to run DHCP PD at each hop down the

What would the signalling look like for R2 to announce (renumber?) to 
its downstream (R3) when R1 delegates to R2?

+---------------+
|    R1 (ISP)   |
+-------+-------+      |
         |              |   2001:db8::/48
         |              |
         |              V
+-------+-------+
|   R2 (Ent.)   |
+-------+-------+
         |              |
         |              |   2001:db8:babe::/52
         |              |
+-------+-------+      V
|   R3 (Site)   |
+---------------+

Mark/

---

From: Andreas Maier <[email-masked]>
Date: Tue, 15 Feb 2005 15:55:03 +0000

Dear Changming,
dear Mark,

thank you for your replies.

On 02/15/05 14:04:43, Mark Thompson wrote:
>> Will this make the PD more complicated, hard to implement and hard  
>> to configure as well? Is it possible to run DHCP PD at each hop down  
>> the tree?

More complicated? No. The mechanism for DHCPv6 PD as of RFC-3633 does  
not need to change. Small additions may be helpful to increase  
resistance against misconfiguration or to enable corner cases.

Hard to implement? Yes. Each intermediate router acts as a DHCP PD  
client and a DHCP PD server at the same time. Additionally it has to  
perform sub-network splitting, aggregation and more.

Hard to configure? No. The configuration of the "root" routers stays  
the same and all other routers need not configuration because they are  
automatically configured through the proposed mechanism.

A requirement would be that each router runs DHCP DP. Intermediate  
routers are hybrid in that they are clients up the tree and servers  
down the tree. Each intermediate router should make subdividing  
decisions on its own and should hide subtree details.

> its downstream (R3) when R1 delegates to R2?

I think that delegations are polled upstream and not pushed downstream.  
In this case R3 would ask R2 for a delegation which in turn may need to  
ask R1 for more prefixes if its pool is exhausted. The prefix pool can  
be managed with a buddy system.

Renumbering should be possible at times where DHCP PD renewals are due.  
Announcements without renumbering seems to be a corner case where R1  
carries independent prefixes from a number of ISPs which should all be  
usable by the sites. For subdividing and aggregation R2 and R3 need to  
know if prefixes are part of the same "master"-prefix or not. This may  
be handled by a DHCP PD extension.

Background information: The scenario that should be handled is the  
following. R1 is controlled by one or more ISPs. R2 is in fact a number  
of hops (routers) in the field so that various R3s at user sites can be  
reached. It should be possible to add or remove R2s and R3s on the fly  
and they should automatically configure themselves. The network spreads  
out from a central point and no meshed connections between R2s and/or  
R3s are expected.

Best regards,
-andi

-- 
| Andreas Maier               Paris-Lodron University of Salzburg   |
| ([email-masked])       Department of Scientific Computing    |
| Tel. +43/662/8044-6339      Jakob Haringerstr. 2                  |
| Fax. +43/662/8044-172       5020 Salzburg / Austria, Europe       |