Subject: RE: [dhcwg] RE: purpose of m/o bit

From: "Templin, Fred L" <[email-masked]>
Date: Thu, 2 Jun 2005 15:00:53 -0700

Jim et al,

At the risk of covering old ground, one question I had is whether a client must wait to receive an RA before initiating stateless or stateful DHCPv6? Asked another way, can DHCPv6 still be used if there are no advertising routers on the link?

To an even more speculative question, if we had it all to do over again would it be possible (or desireable) to design things such that DHCPv6 and IPv6 ND messages could be "piggybacked" within a single packet? (This begs the question of whether the DHCPv6 server/relay and IPv6 router entities are co-resident on the same node in the normal case.)

Fred
[email-masked]    

"Bound, Jim" <[email-masked]> wrote:
> > It would be really nice and handy to initiate either stateless or
> > stateful DHCPv6 with the same message. If so, we wouldn't need
> > the M/O bits anymore. In this case the client would simply initiate
> > a(n Information) Request message and would get all the information
> > that are available on the link, including an address or not.
>
> So you don't believe that the RA in ND should be the authority to use a
> stateful model on an IPv6 link?
>
> /jim

--------------------------------------------------------------------
IETF IPv6 working group mailing list
[email-masked]
Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6
--------------------------------------------------------------------

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Fri, 3 Jun 2005 10:00:50 +0200

On 3-jun-2005, at 0:00, Templin, Fred L wrote:

> At the risk of covering old ground,

Yeah, we wouldn't want that.  :-)

> one question I had is whether a client must wait to receive an RA  
> before initiating stateless or stateful DHCPv6?

How would it know the value of the M and O bits if it didn't?

> Asked another way, can DHCPv6 still be used if there are no  
> advertising routers on the link?

I suppose nothing is impossible, but it won't buy you much. If you  
get an address, you can't use it, since DHCPv6 can't provide a  
default gateway, like DHCPv4 does. Being able to learn additional  
information is of questionable value, using multicast DNS / zeroconf  
would be much more appropriate in an environment where there is no  
global connectivity.

> To an even more speculative question, if we had it all to do over  
> again would it be possible (or desireable) to design things such  
> that DHCPv6 and IPv6 ND messages could be "piggybacked" within a  
> single packet?

There is obvious synergy here.

I think we can still do this, and it could be very simple: define a  
new RA/ND option that carries DHCPv6 options. Routers could inject  
locally configured information, or do some form of stateless DHCPv6  
and copy the results to RAs. (Stateful information must not leak out  
through RAs, of course.)

Note that information in RAs is broadcast periodically so it takes up  
some bandwidth regardless of whether it's needed. On the other hand,  
hosts don't have to query for this information individually, which  
saves bandwidth, especially on a shared medium such as 802.11.