DHCPv6 PD

David W. Hankins David_Hankins at isc.org
Tue May 5 15:20:03 CDT 2009


On Tue, May 05, 2009 at 02:49:01PM -0500, Jack Bates wrote:
> Sure, but how does the router know it needs to hand out a /62? Then what 
> about the router after that? Does it hand out a /61? then the router behind 
> that?

In IA_NA's, there is a (undocumented in RFC 3315) convention to permit
a client to supply an IAADDR with a zeroed address.  This convention
allows the client to supply preferred and valid lifetime hints without
knowing a specific address it would like.

I see no reason why a similar convention can't take root here; the
bottom-most client supplies an IAPREFIX in its IA_PD with a zeroed
network number, and the desired prefix length (suppose: /64 for its
one downstream interface).  The next hop combines the sum total of
bitspaces required by its clients and presents a suitable requested
size upstream (with memory, and resizing/renumbering as you go).

> What if the ISP only gave a /60?

Then someone gets a STATUS_NoAddrsAvail.

-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins
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