Re: draft-wbeebee-ipv6-cpe-router-04 comments

[Ole Troan <otroan@employees.org>]

James,

>>> We use Router Advertisement messages, instead of some other protocol like
>>> RIP [RFC2080], because Router Advertisements are an existing standard,
>>> stable protocol for router-to-host communication. Piggybacking this
>>> information on existing message traffic from routers to hosts reduces
>>> network overhead. Neighbor Discovery shares with Multicast Listener
>>> Discovery the property that they both define host-to-router interactions,
>>> while shielding the host from having to participate in more general
>>> router-to-router interactions. In addition, RIP is unsuitable because it
>>> does not carry route lifetimes so it requires frequent message traffic
>>> with
>>> greater processing overheads.
>>
>> indeed. MSR is a router-to-host mechanism. the CPE acts for some
>> purposes as a host on the upstream interface. do you expect the MSR
>> routes to be limited to be used only for the host part of the CPE (i.e
>> communication originating from the CPE) or to make it into the CPE's
>> forwarding table?
>
>
> Yes, naturally.  Why not?

because we have protocols doing that already? (RIP, OSPF, ISIS, BGP...)

> If I were planning to implement a CPE router that processed received RA with
> RFC 4191 MSR options, I'm pretty sure I would do it so that the routes used
> by the node implementation were the same routes used by the forwarding
> implementation.  It would be a lot of extra hassle to maintain two route
> tables, and the payoff would seem quite unclear to me.

iff you wanted to make ND into a routing protocol using MSRs, I
believe you would have to change RFC4191. and possibly the main ND
spec, as routers doesn't listen to ND.

if I understand this draft correctly it behaves both as a host (doing
address assignment) and as a router (forwarding packets) on the
upstream interface. that behaviour isn't described in RFC4861. I don't
see any harm in e.g doing SLAAC as that's purely a host function.
processing MSR routes on the other hand configures the router.

Ole