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

On Wed, 2 Dec 2009, Ole Troan wrote:


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? 

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? 

"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. 

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

--
Mikael Abrahamsson    email: swmike@swm.pp.se