Re: [v6ops] I-D Action: draft-ietf-v6ops-conditional-ras-01.txt

[Jen Linkova <[e-mail]>]

On Thu, Mar 22, 2018 at 6:26 AM, 神明達哉 <[e-mail]> wrote:
>> > [[Dusan]] This is an implementation aspect. If hosts implement the Prf
>> > from rfc4191#section-2.2, they will recognize Rrf. You should not limit the
>> > options based on the current implementations.
>>
>> Actually, we should. This is an operational working group, and as such,
>> needs to document practices that work today.
>
> I've not closely followed this thread so this may be out of context
> (if so, sorry), but if it's about host implementation of the "Prf"
> value of RFC4191, BSD variants have been supporting it for more than
> 10 years (for example, FreeBSD added it in 2006
> https://svnweb.freebsd.org/base/head/sys/netinet6/nd6_rtr.c?revision=156871&view=markup).
> So I suspect it's also in iOS.  Unlike other features of
> the RFC like route information option, implementing Prf is pretty
> simple, so I wouldn't be surprised if it's also available in non
> BSD-flavor host implementations.

Yeah, you are right, it's reasonably well supported. The issue here is
that just using router preference would not help at all (or may even
make the routing more sub-optimal). Let's say a host honors the router
preference and selects a router  R1 (connected to an ISP1) as a
default gateway but it does not support Rule 5.5, then it may select
ISP2 source prefix and the packet will be send to ISP2 ( R1 -> R2 ->
ISP2). So I'm not sure I can see any value in using the router
preference w/o rule 5.5 support in this scenario..Am I missing
anything?


-- 
SY, Jen Linkova aka Furry