Re: [v6ops] draft-ietf-6man-grand : saving lookups

Jen Linkova <> Wed, 12 August 2020 03:54 UTC

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From: Jen Linkova <>
Date: Wed, 12 Aug 2020 13:54:16 +1000
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To: Philip Homburg <>
Cc: V6 Ops List <>, 6man <>
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Subject: Re: [v6ops] draft-ietf-6man-grand : saving lookups
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On Tue, Aug 11, 2020 at 6:28 PM Philip Homburg
<> wrote:
> In your letter dated Sun, 9 Aug 2020 19:28:51 +1000 you wrote:
> >I guess we can add to the very end of the Section 4.1.2 (the new text):
> >"A node MAY send unsolicited NAs for its preferred addresses
> >periodically to refresh the Neighbor Cache on the first hop routers."
> >
> >On the other hand it might pollute the router NC with entries for
> >addresses which the node has configured but is not going to use.
> >
> >What does the WG think?
> A few thoughts:
> 1) It has to specified how often the host has to refresh entries

Yes, and it would be very tricky because (as I've mentioned in another
email in this thread) finding the useful interval requires knowing the
timers for NC garbage collection on routers.

> 2) I think MAY is too weak to rely on. One possibility to deal with 1)
>    and 2) is to have an RA option that specifies the interval. Then we
>    can make sending the NAs if the option is present a SHOULD or MUST

I'm not convinced we shall be doing it in the first place ;) And MUST
or even SHOULD look like a very strong requirement on all hosts just
to cover the very special case of sleeping devices.

> 3) What happens if there are more entries then fit in the router's NC?

I guess the same thing which happens in other scenarios when  the
router is trying to create an entry and there is no free space.

> 4) It has been argued against DHCPv6 IA_NA that hosts may need more
>    addresses than can be handled by the DHCP server. There is an RFC
>    that says something to that effect. If so, then we can expect
>    more address than can be handled by the router NC as well. I think
>    we need to be consistent here. Or is this only for some special
>    networks where host have only few addresses?
>    can also expect hoss

Yes, I agree. Normally when a host *assigns* an address it's very
likely that the host is going to use it soon.
Periodic announcements for all preferred addresses does look like an
overkill to me.

> 5) Hosts have to inform all routers, so this would require hosts to track
>    all routers and just a few of them

I'm not sure about this - ff02::2 should work.

> 6) It seems to me that this would something for a new draft

i totally agree.

SY, Jen Linkova aka Furry