Subject: RE: [dhcwg] Delegated prefix managed by multiple entities

From: "Woundy, Richard" <[email-masked]>
Date: Thu, 15 Feb 2007 04:10:33 -0500

>Especially in the multi-homed case, anything other than the latter
solution is broken by design.

Yes, I totally agree, that was my point.

>If you want to multi-home, you have to expect to run a real routing
protocol on the customer's router.

Sigh. If that is required (I'm not sure I totally agree, but I
understand why you make that assertion), then I suspect that (1)
multi-homed customers shouldn't bother using DHCP-PD (they must
configure their edge router manually in all cases - sorry), and/or (2)
the DHCP-PD protocol solution needs to be reworked to configure both
sides of the routing adjacency (RIP, OSPF/IS-IS, or BGP) between the ISP
Edge Router and the customer router.

I think the former choice is giving up. But that's just my opinion.

For the latter choice, I think that Ole just might be on the right
track:

>if an "end-to-end" DHCP infrastructure is wanted, I suppose one could
use a DHCP proxy on the edge device. Server downstream, client upstream.
that should take care of the state maintenance issues that came up with
the RAAN proposal.

-- Rich

-----Original Message-----
From: Chuck Anderson [mailto:[email-masked]] 
Sent: Thursday, February 15, 2007 2:37 AM
To: dhcwg
Subject: Re: [dhcwg] Delegated prefix managed by multiple entities

On Thu, Feb 15, 2007 at 12:23:33AM -0700, Ted Lemon wrote:
> >You need routability for the prefixes handed via PD; whether the
> >route is
> >valid for the lease lifetime, or only when the interface is really
> >reachable (information not always available, subject to crashes  
> >somewhere
> >on the path, etc) is a matter of preference..
> 
> Clearly the latter is preferable to the former, all other factors
> being equal.

Being a network engineer, I have to agree with Ted here.  Especially 
in the multi-homed case, anything other than the latter solution is 
broken by design.  If you want to multi-home, you have to expect to 
run a real routing protocol on the customer's router.  I would be 
strongly against any attempt to piggyback routing on top of DHCP.

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From: Markus Stenberg <[email-masked]>
Date: Fri, 16 Feb 2007 12:36:14 +0900

>> that should take care of the state maintenance issues that came up with

Yes. There's the eternal argument of proxy state machine complexity, but
I'm willing to bet that it isn't orders of magnitude more complex than
'stateful' relay in and of itself. 

And given the choice of 'bit more complex, but well understood and correct'
versus 'simple hack, but mostly works', I'd go for the former.

Of course, it doesn't remove the routing maintenace problems (due to
potential lack of l2 link state knowledge in the first-hop server), but it
makes life considerably easier; all you need is .. love? (not really; BFD
on the client.)

-Markus