Re: [dhcwg] Informational IPv6 prefix option for DHCPv6

["Templin, Fred L" <[e-mail]>]

Hi Bernie,

Thanks. At first glance, this looks like it is too tightly wrapped
around DHCPv6 PD for what I am after. I want something very simple
that is somehow related to PD but at the same time independent of PD.

So again, to my link model, I have a link on which there are one
or more delegating routers and lots and lots of requesting routers.
To get the information I am looking for, I could set the delegating
routers to include the aggregated prefix in RA PIOs with the 'A' and
'L' bits set to 0. But, that means that I would need to set up some
manual configuration on each of the delegating routers and I really
don't want to have to do that.

Much better would be to have the DHCPv6 server include the aggregated
prefix in a simple informative DHCPv6 option as a single administrative
touch point. The delegating routers are then simpler and less prone to
misconfigurations, and the requesting routers get the PD and aggregated
prefix information they need in a single DHCPv6 request.

I think a while back there was some discussion about including PIOs in
DHCPv6 messages. Did that hit some kind of roadblock? Because, I think
I now have an interesting use case for it.

Thanks - Fred
[e-mail]

> -----Original Message-----
> From: Bernie Volz (volz) [mailto:[e-mail]]
> Sent: Monday, July 07, 2014 12:57 PM
> To: Templin, Fred L; Andre Kostur
> Cc: [e-mail]
> Subject: RE: [dhcwg] Informational IPv6 prefix option for DHCPv6
> 
> There was a draft to do something like this. But I think it died. See
> http://tools.ietf.org/html/draft-ietf-dhc-dhcpv6-prefix-pool-opt
> 
> - Bernie
> 
> -----Original Message-----
> From: dhcwg [mailto:[e-mail]] On Behalf Of Templin, Fred L
> Sent: Monday, July 07, 2014 3:44 PM
> To: Andre Kostur
> Cc: [e-mail]
> Subject: Re: [dhcwg] Informational IPv6 prefix option for DHCPv6
> 
> Hi Andre,
> 
> > -----Original Message-----
> > From: Andre Kostur [mailto:[e-mail]]
> > Sent: Monday, July 07, 2014 12:27 PM
> > To: Templin, Fred L
> > Cc: [e-mail]
> > Subject: Re: [dhcwg] Informational IPv6 prefix option for DHCPv6
> >
> > Then I'm not sure of the purpose of this information.  The client got
> > an IPv6 address from somewhere, so it should be able to know its
> > prefix from that.  What's the client supposed to do with this
> > information that it's getting from DHCP?
> 
> It is for a link type on which there is no non-link-local IPv6 prefix assigned. The link connects a
> bunch of routers that only configure a link-local address on the link. The routers also act as DHCPv6
> clients, and act as requesting routers using DHCPv6 PD to get a prefix to assign to their downstream
> attached links.
> 
> The IPv6 prefix I want to include in the DHCPv6 option I am asking for is the aggregated prefix from
> which client prefixes are delegated. So, if the aggregated prefix is 2001:db8::/32, then the clients
> would be delegated longer prefixes such as 2001:db8:4000::/48, 2001:db8:1::/56, 2001:db8:21:31::/64,
> etc.
> 
> So, the aggregated prefix is not assigned *to* the link, but rather tells the set of prefixes that can
> be reached *through* the link.
> This is important information that I want to provide to the clients via a DHCPv6 option.
> 
> Thanks - Fred
> [e-mail]
> 
> > On Mon, Jul 7, 2014 at 11:52 AM, Templin, Fred L
> > <[e-mail]> wrote:
> > > Hi Andre,
> > >
> > > No, this is not Prefix Delegation. For PD, the DHCPv6 server returns
> > > an IPv6 prefix that the client then uses to number its
> > > downstream-attached links. What I want is an informational option
> > > that pertains to the link over which the client contacts the server,
> > > and to my understanding PD cannot be used for that.
> > >
> > > Thanks - Fred
> > > [e-mail]
> > >
> > >> -----Original Message-----
> > >> From: Andre Kostur [mailto:[e-mail]]
> > >> Sent: Monday, July 07, 2014 11:23 AM
> > >> To: Templin, Fred L
> > >> Cc: [e-mail]
> > >> Subject: Re: [dhcwg] Informational IPv6 prefix option for DHCPv6
> > >>
> > >> Isn't that Prefix Delegation? RFC 3633.  Nutshell is that the
> > >> client can specifically ask the server for a prefix.  Part of the
> > >> plan is for routers deployed out at the edge, and they can ask the
> > >> DHCP server for a prefix that the router will then manage on its
> > >> further downstream links.
> > >>
> > >> On Mon, Jul 7, 2014 at 10:54 AM, Templin, Fred L
> > >> <[e-mail]> wrote:
> > >> > Hi,
> > >> >
> > >> > I am looking for a DHCPv6 option that a server can use to report
> > >> > an IPv6 prefix to a client. This *would not* be used as a
> > >> > replacement for Router Advertisement Prefix Information Options
> > >> > (PIOs), and the client *would
> > >> > not* use the prefix for SLAAC.
> > >> >
> > >> > A DHCPv6 option that specifically returned an IPv6 prefix (along
> > >> > with prefix length) would be preferred. A DHCPv6 option that
> > >> > returned opaque data could also be used as a kludge but I would
> > >> > rather not have to do that. Is there a DHCPv6 option that would meet these requirements?
> > >> >
> > >> > Thanks - Fred
> > >> > [e-mail]
> > >> >
> > >> > _______________________________________________
> > >> > dhcwg mailing list
> > >> > [e-mail]
> > >> > https://www.ietf.org/mailman/listinfo/dhcwg
> > >>
> > >>
> > >>
> > >> --
> > >> Andre Kostur
> >
> > --
> > Andre Kostur
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