Re: [v6ops] WGLC: draft-ietf-v6ops-unique-ipv6-prefix-per-host-02 - multiple prefixes per device

[Alexandre Petrescu <[e-mail]>]

Le 20/03/2017 à 12:46, Ross Chandler a écrit :
>
>> On 20 Mar 2017, at 09:28, Lorenzo Colitti <[e-mail]>
>> wrote:
>>
>> Given that this is an operational draft, then I would suggest an
>> applicability statement: state that DHCPv6 PD is better, but also
>> state that best *current* practice is to provide a /64 via RA,
>> because currently very few hosts have DHCPv6 PD clients and
>> providing PD on the network side is not going to help the vast
>> majority of clients.
>>
>> Using shared links on public deployments with untrusted hosts has
>> all sorts of security and scalability issues (ND spoofing, DAD
>> spoofing, ND cache exhaustion attacks, etc.) /64 to the host is
>> just a much better solution.
>
>
>
> It might also be worth noting in the draft how 3GPP TS.23401
> 5.3.1.2.6  says prefix shorter than /64 assignment to UEs should
> work.

A-ha!

> "Optionally a single network prefix shorter than the default /64
> prefix may be assigned to a PDN connection. In this case, the /64
> default prefix used for IPv6 stateless autoconfiguration will be
> allocated from this network prefix; the remaining address space from
>  the network prefix can be delegated to the PDN connection using
> prefix delegation after the default bearer establishment and IPv6
> prefix allocation via IPv6 stateless address autoconfiguration as
> defined in clause 5.3.1.2.2.”
>
> “The UE uses DHCPv6 to request additional IPv6 prefixes (i.e.
> prefixes in addition to the default prefix) from the PDN GW after
> completing stateless IPv6 address autoconfiguration procedures.”

This seems to indicate that the PDN GW plays both a role of
DHCPv6-PD Requesting Router aka DHCPv6 Client (when it gets "assigned" a
shorter-than-64 prefix) _and_ the role of
DHCPv6-PD Delegating Router aka DHCPv6 Server (when it delegates
additional IPv6 prefixes to the UE).

This is a little bit awkward for setting up routing.

It would be simpler if the PDN GW were a DHCPv6 Relay.

Has it been considered to make the PDN GW a DHCPv6 Relay?

> Having a single contiguous prefix is allowed for by specifying the
> minor extra detail of prefix length in CDRs.

It makes sense to have a single contiguous prefix, in some cases.

It could also make sense to set an entire /47 to that PDN GW, and run a
DHCPv6 Server on PDN GWs and nowhere else.

It comes down to these two non-awkward options: either set a DHCPv6
Server in each PDN GW, or a single DHCPv6 Server deeper in the core
accompanied by many DHCPv6 Relays in each PDN GW.

Alex

>
> Ross
>
>
>
> _______________________________________________ v6ops mailing list
> [e-mail] https://www.ietf.org/mailman/listinfo/v6ops
>