Re: CPE router draft: Default route and WAN interface provisioning

[Ole Troan <otroan@employees.org>]

Mikael,

thanks for the comments, see inline.

>> as the editor of the draft-ietf-v6ops-ipv6-cpe-router let me bring the following questions to the list.
>> 
>> the IPv6 CE router WAN interface needs to acquire addresses i.e behave like a host if one follows the definition in RFC4862. it forwards traffic out this interface so it is also a router.
>> we don't want to redefine the host/router definitions in 4861/4862. for the purposes of address assignment of a router interface, is this text acceptable and clear:
>> 
>>  "When the router is attached to the WAN interface link it must act as
>>  an IPv6 host for the purposes of stateless or stateful interface
>>  address assignment ([RFC4862]/[RFC3315]).  The router acts as a
>>  requesting router for the purposes of DHCP prefix delegation
>>  ([RFC3633])."
> 
> How does this work together with:
> 
> "WAA-6:  If the IPv6 CE router does not acquire a global IPv6 address
>           from either SLAAC or DHCP, then it MUST create a global IPv6
>           address from its delegated prefix and configure that on one
>           of its internal virtual network interfaces."
> 
> Does it only mean that it must potentially act as a host and try to get an IPv6 address, but it's ok if it doesn't ? Is it possible that people will be confused by this and it needs more clarification? Should it also say that this virtual network interface must be used to source traffic from the CPE router to the WAN side?

what we are trying to say is that the IPv6 CE router MUST try to acquire an address on its WAN interface using SLAAC and/or DHCP. if that fails then it MUST create an address from the delegated prefix. this should allow for all addressing models, including the one where the WAN link is not numbered with globally scoped addresses.
please feel free to suggest better text.

with regards to source address selection. it might be prudent to state that the IPv6 CE router supports the weak host model and can use a source address from a different interface than the interface the packet is sent out of.

> Then the wording here:
> 
> "WPD-3:  If the delegated prefix is an aggregate route of multiple,
>           more-specific routes the IPv6 CE router MUST discard packets
>           that match the aggregate route, but not any of the more-
>           specific routes.  In other words, the "next-hop" for the
>           aggregate route should be the null destination.  This is
>           necessary to prevent forwarding loops when some addresses
>           covered by the aggregate are not reachable.  [RFC4632]"
> 
> Would it make sense to specifically say that any PD space received must be null routed unless it's used on an interface or routed somewhere else (sub-PDed to another router in the home)? Just in case multiple PDs are received and a LAN interface goes down?

that's what we are trying to say. i.e that you have a null route for the aggregate, aka the delegated prefix. parts of this text is from rfc4632. any improved proposed text would be appreciated.

> "L-5:  The IPv6 CE router must assign a separate /64 from its
>         delegated prefix (and ULA prefix if configured to provide ULA
>         addressing) for each of its LAN interfaces.  The IPV6 CE router
>         MUST make the interface an advertising interface according to
>         RFC4861.  In router advertisements messages, the Prefix
>         Information Option's A/L-bits MUST be set to 1 by default; the
>         A/L bits setting SHOULD be user configurable."
> 
> Does "LAN interface" refer to physical or vlan interface? What if the home CPE has 8 LAN ports and the user would like port 1-3 to be in the same vlan and thus share the same /64. Does this wording prohibit this behaviour? There is a "must" (shouldn't that be capital letters?) in there... I think the behaviour of having multiple ports in the same /64 and do L2 switching between them should be allowed.

we have received multiple comments on this. suggestions are welcome!
since this is a router I thought it obvious that whenever we talked about an interface it would be clear that it was a   L3 routed interface connected to an IPv6 link. this document does not concern itself with bridging or switches on L2. e.g a typical IPv6 CE router would have 4 downstream Ethernet ports, but these are typically switched and represented as a single IPv6 LAN interface.


> 
> Otherwise I think the document is a fine piece of work! :)

thanks!

Best regards,
Ole