Re: [v6ops] Calling the question: draft-ietf-v6ops-host-addr-availability-03.txt

[Mark Smith <[e-mail]>]

On 22 December 2015 at 07:07, Philip Homburg <[e-mail]> wrote:

<snip>
>
>>If your concern is that using DHCPv6 PD on a host will cause lots of
>>problems - what problems are you talking about? From the host perspective
>>it's simple. You get a prefix.
>
> I described it earlier:
> - A host gets a prefix from DHCPv6 relay. The relay reboots, does the
>   relay have a persistent store of the PD leases or is the host expected
>   to poll?
>
>   As far as I know, there is no text in RFC 3633 that requires persistent state
>   in a DHCPv6 relay. Maybe I missed something.
>
>   If the host is expect to poll, how does that work. You mention Windows,
>   how do they deal with this problem.
>

How do CPE using DHCPv6-PD deal with this problem (because they do)?


> - And to spice it up, how do redundant routers, acting as DHCPv6 relays and
>   one of them is shutdown. Again is this something the network has
>   to handle, or is this the resposibility of the host. It is just not
>   documented. If PD for hosts is used in practice, then somebody must have
>   dealt with this problem.
>

How do CPE using DHCPv6-PD deal with this problem (because they do)?


I think you and others might be making this problem harder than it is.
These "hosts" using DHCPv6-PD are really no more than routers that are
only forwarding packets they originate from an internal interface,
such as NTP, DNS or SIP for a POTS port.

RFC6204 ("Basic Requirements for IPv6 Customer Edge Routers") from
2011 described how the CPE was to use some of its delegated space to
for its own purposes, assigned to an internal virtual network:


WAA-8:  If the IPv6 CE router does not acquire global IPv6
           address(es) from either SLAAC or DHCPv6, then it MUST create
           global IPv6 address(es) from its delegated prefix(es) and
           configure those on one of its internal virtual network
           interfaces.

So take that spec, disconnect the LAN interface, and you have a "host"
using DHCPv6-PD that is only sending and receiving traffic for its own
locally running applications.

The only gap I can see is in the multicast domain because ISPs don't
provide multicast routing services to routers that aren't running a
fully fledged multicast routing protocol. So if we want to solve that
without requiring the <strike>CPE</strike>hosts to run PIM, we either
need to send MLD messages for the internal network group membership on
the <strike>WAN</strike>physical LAN interface of the
<strike>CPE</strike> host, or have a mechanism in DHCPv6 performs the
equivalent multicast function.

I agree that detail like that probably shouldn't be in this draft,
however I don't think this is such an unknown and un-understood
scenario that mentioning DHCPv6-PD as a possible method to facilitate
it is a problem.

Regards,
Mark.