Re: I-D Action:draft-ietf-v6ops-ipv6-cpe-router-02.txt

[Ole Troan <otroan@employees.org>]

Hiroki,

[...]

> ot> for the purposes of SLAAC, router discovery etc it should always act
> ot> as a host on the WAN interface. it should not reply to RS messages nor
> ot> set the R-bit in NAs.
>
>  Thank you for the clarification.  Correct me if I am wrong, but in my
>  understanding, for router discovery and SLAAC the node must
>  accept/process RAs and must discard received RSes.  This means
>  "acting as a host", but is there a technical reason to always set
>  R-bit in NAs zero?  A CE router has a moment of transition from a
>  host to a router (after provisioning, for example) and vice versa as
>  viewed from the PE router, so making R-bit depend on whether IP
>  forwarding is enabled or not still seems reasonable to me.

I don't think you can say that there is a transition from a host to a
router. it is performing functions of both at the same time, all the
time. e.g it will continue to process received RAs as long as the
interface is up...

>  Even if doing so the R-bit should not prevent the CE router from
>  router discovery or SLAAC.  While pretending a host by always setting
>  the R-bit zero would work certainly, to me there is no strong reason
>  to disable the functionality.

to turn the question around, why would you want to enable the flag?
for these types of links it is unlikely to be another host there, even
so I would avoid any situation where a host on the WAN link would end
up using the CE router as its default router.

the IPv6 CE router MUST not send RA messages on the WAN interface of
course, nor enable any routing protocol to attract traffic.

>  So, I think acting as a host with regard to RS/RA is needed on WAN
>  interface, but NS/NA do not always need to do so.  Is this a wrong
>  idea?  What I mean in writing is something like the following:
>
>  | When the router is attached to the WAN interface link it must act as
>  | an IPv6 host for the purposes of IPv6 interface initialisation, ND
>  | Router Discovery, Prefix Discovery and interface address assignment
>  | ([RFC4861]/[RFC4862]) except that the Router flag in Solicited
>  | Neighbor Advertisement messages MUST be set to one if IP forwarding
>  | is enabled; otherwise it MUST be set to zero ([RFC4861] Section 7.2.4).

Best regards,
Ole