Re: I-D Action: draft-ietf-6man-rfc6434-bis-01.txt

[Erik Kline <[e-mail]>]

On 16 July 2017 at 18:31, Lorenzo Colitti <[e-mail]> wrote:
> On Mon, Jul 3, 2017 at 5:40 PM, <[e-mail]> wrote:
>>
>> A New Internet-Draft is available from the on-line Internet-Drafts
>> directories.
>> This draft is a work item of the IPv6 Maintenance of the IETF.
>>
>>         Title           : IPv6 Node Requirements
>>         Authors         : Tim Chown
>>                           John Loughney
>>                           Timothy Winters
>>         Filename        : draft-ietf-6man-rfc6434-bis-01.txt
>
>
> I see that the document still says:
>
>    There will be a wide
>    range of IPv6 deployment models and differences in address assignment
>    requirements, some of which may require DHCPv6 for stateful address
>    assignment.  Consequently, all hosts SHOULD implement address
>    configuration via DHCPv6.
>
> We should abandon this documentation, for two reasons.
>
> First, networks that require DHCPv6 assignment are explicitly NOT
> RECOMMENDED by current IETF best practices. Specifically, RFC 7934 section 8
> says "it is RECOMMENDED that the network give the host the ability to use
> new addresses without requiring explicit requests". A DHCPv6-only network
> cannot meet this recommendation, because on a DHCPv6-only network, all
> addresses acquisition requires an explicit request to the network.
>
> Second, the draft says "Where devices are likely to be carried by users and
> attached to multiple visisted networks, DHCPv6 client anonymity profiles
> SHOULD be supported as described in [RFC7844]".
>
> But RFC 7844 says that hosts SHOULD prefer stateless address configuration
> over DHCPv6: "hosts using the anonymity profile SHOULD use stateless address
> configuration instead of stateful address configuration".
>
> So for such devices, there is a direct conflict: this document says they
> SHOULD do DHCPv6, but RFC 7844 says they SHOULD not if other addressing
> modes are available.
>
> I would propose the following text for section 6.5:
>
>    [...] There will be a wide
>    range of IPv6 deployment models and differences in address assignment
>    requirements, some of which may use DHCPv6 for stateful address
>    assignment in addition to other addressing modes. Using DHCPv6 as the
>    only IPv6 address configuration mechanism is NOT RECOMMENDED
>    [RFC 7934 section 8].
>
>    In the absence of a router, IPv6 nodes using DHCP for address
>    assignment MAY initiate DHCP to obtain IPv6 addresses and other
>    configuration information, as described in Section 5.5.2 of
>    [RFC4862].
>
>    Where devices are likely to be carried by users and attached to
>    multiple visisted networks, DHCPv6 client anonymity profiles SHOULD
>    be supported as described in [RFC7844] to minimise the discolosure of
>    identifying information. This profile recommends that the device prefer
>    stateless address configuration over DHCPv6 address configuration.
>
>    Devices that do not have particular anonymity requirements SHOULD
>    implement address configuration via DHCPv6 in order to be able to
>    take advantage of IPv6 addresses available only via DHCPv6.

Sounds good to me.

I also think that section 5.9 on RFC 4191 should be a MUST.  We don't
want to end up in a situation where routers are sending out PIOs with
/56s and L=0 in order to maintain internal connectivity when RAs have
default_router_lifetime=0, e.g. because the upstream network has gone
away.