Re: [v6ops] I-D Action: draft-ietf-v6ops-unique-ipv6-prefix-per-host-11.txt

[David Farmer <[e-mail]>]

On Thu, Sep 28, 2017 at 12:00 PM, Fred Baker <[e-mail]>
wrote:

>
>
> > On Sep 28, 2017, at 7:08 AM, David Farmer <[e-mail]> wrote:
> >
> > I like most of the changes, however I find the following bullet somewhat
> confusing;
> >
> > o  Maximum IPv6 Router Advertisement Interval = 300s (or when battery
> >    consumption is a concern then a MinRtrAdvInterval of 514 seconds
> >    (1/7 of an hour) is better according RFC7772 [RFC7772]).
> >
> > It starts out talking about the *Maximum* Router Advertisement Interval,
> then with little explanation shifts to talking about the *Minimum* Router
> Advertisement Interval, I fear this will easily confuse any casual
> readers.  Furthermore, the IPv6 router implementations I'm familiar with,
> don't allow you to directly set the Minimum Router Advertisement Interval,
> it is automatically computed as 75% of the Maximum Router Advertisement
> Interval, as recommended in RFC4861. Therefore, in such implementations the
> Maximum Router Advertisement Interval would need to be set at 685 seconds.
> >
> > Also, as Lorenzo pointed out, there is no discussion of IPv6 Router
> LifeTime, which is also discussed in RFC7772.
>
> The bit about the inter-router-advertisement interval was at my
> suggestion. Lorenzo had complained that the draft didn't do anything to
> meet RFC 7772. That was changed somewhere between -07 and -10. However, it
> resulted in only specifying MaxRtrAdvInterval. If we want to have no more
> than seven RAs per hour (per RFC 7772), it is MinRtrAdvInterval that is
> important. 514=3600/7, hence the specification of MinRtrAdvInterval.
>
> May I suggest you suggest text? What would you like it to say?
>

I did suggest some text, but I didn't correctly remembered what RFC4861
says, so how about this;

o  Maximum IPv6 Router Advertisement Interval (MaxRtrAdvInterval) = 300s
(or when battery
    consumption is a concern 686s, see Note below)

o  IPv6 Router LifeTime = 3600s (see Note below)

...

Note: When servicing large numbers of battery powered devices, RFC7772
suggests a maximum of 7 RAs per hour and a 45-90 minute IPv6 Router
Lifetime. To achieve a maximum of 7 RAs per hour, the Minimum IPv6 Router
Advertisement Interval (MinRtrAdvInterval) is the important parameter, and
MUST be greater than or equal to 514 seconds (1/7 of an hour). Further as
discussed in RFC4861 section 6.2.1, MinRtrAdvInterval <= 0.75 *
MaxRtrAdvInterval, therefore MaxRtrAdvInterval MUST additionally be greater
than or equal to 686 seconds. As for the recommended IPv6 Router Lifetime,
since this technique requires that RAs are sent using the link-layer
unicast address of the subscriber, the concerns over multicast delivery
discussed in RFC7772 are already mitigated, therefore the above suggestion
of 3600 seconds (an hour) seems sufficient for this use case.


This keeps the table compact and easily understandable, providing the
details in a paragraph following the table.

Thanks.


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