RE: [v6ops] Combining IPv6 ND and DHCPv6 into a single, unified function

"Templin, Fred L" <Fred.L.Templin@boeing.com> Tue, 28 November 2017 17:02 UTC

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From: "Templin, Fred L" <Fred.L.Templin@boeing.com>
To: "STARK, BARBARA H" <bs7652@att.com>, Fred Baker <fredbaker.ietf@gmail.com>, Michael Richardson <mcr+ietf@sandelman.ca>
CC: "dhcwg@ietf.org" <dhcwg@ietf.org>, "v6ops@ietf.org" <v6ops@ietf.org>, "6man@ietf.org" <6man@ietf.org>
Subject: RE: [v6ops] Combining IPv6 ND and DHCPv6 into a single, unified function
Thread-Topic: [v6ops] Combining IPv6 ND and DHCPv6 into a single, unified function
Thread-Index: AdNiReoj4OrwrQYST+iGtIF1uM57NgAkcdkAADO+44AAEoFNVAD1MWEAACiUpcA=
Date: Tue, 28 Nov 2017 17:02:17 +0000
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Hi, if there is some concern about backwards compatibility and accepting
configuration information from multiple sources the scenario is as follows:

- the host MAY include a DHCPv6 Request option in its RS message
- routers that do not recognize the DHCPv6 Request option, or that
   do not implement a DHCPv6 relay or server, ignore the option and
   return an RA with no DHCPv6 option and with M/O bits set as normal
- routers that recognize the DHCPv6 Request option and that implement
   a DHCPv6 relay or server process the DHCPv6 Request then include a
   DHCPv6 Reply option in unicast RAs that they send back to the host
- the host processes the RA message and also processes the DHCPv6
   Reply while accepting the union of the configuration information
   provided by both IPv6 ND and DHCPv6

Note that there will never be a time that a router includes a DHCPv6 Reply
option in its RA message unless the host first included a DHCPv6 Request
option in its RS. And, even if it did, hosts that do not recognize the option
will simply ignore it and process the rest of the RA message as normal.

The approach is therefore fully backwards compatible and provides
the best combination of both IPv6 ND and DHCPv6 autoconfiguration.

Thanks - Fred

> -----Original Message-----
> From: dhcwg [mailto:dhcwg-bounces@ietf.org] On Behalf Of STARK, BARBARA H
> Sent: Monday, November 27, 2017 5:20 AM
> To: Fred Baker <fredbaker.ietf@gmail.com>om>; Michael Richardson <mcr+ietf@sandelman.ca>
> Cc: dhcwg@ietf.org; v6ops@ietf.org; 6man@ietf.org
> Subject: Re: [dhcwg] [v6ops] Combining IPv6 ND and DHCPv6 into a single, unified function
> 
> > > My understanding is that Fred Templin essentially wants to carry DHCP
> > > (configuration) options in ND/RA.
> >
> > On thing that I have never understood is the lack of an RA option that carries
> > any DHCPv6 option. This entire silly debate would end if RAs encompassed
> > DHCP options.
> 
> Thus forcing either routers or hosts (or both) to support two distinct mechanisms to do the same thing if there is to be any hope of
> interoperability. And if the host supports both, then it also needs to implement code for which wins when both are present and the
> options provided have conflicting info.
> If you really want DHCPv6 options in RAs for closed ecosystem use cases, include a huge caveat that routers are not required to
> support both mechanisms -- routers are only required to do DHCPv6. Any host that only implements receipt of DHCPv6 options via RA
> must not expect to operate in an open ecosystem. Put the burden on the hosts.
> Barbara
> 
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