Re: [v6ops] [dhcwg] IPv6-Only Preferred DHCPv4 option

[Lorenzo Colitti <[e-mail]>]

On Thu, Dec 5, 2019 at 10:12 AM Roy Marples <[e-mail]> wrote:

> > The draft covers that scenario. DHCPv4 is disabled for V6ONLY_WAIT
> seconds.
>
> Is the wait seconds even needed?
> Just set the T2 timer and treat it as leasing the unspecified address.
> Less data on the wire, less churn in DHCP clients. V6ONLY_WAIT provides
> nothing of value as I see it.
>

I think there is value because the two are conceptually different.

The T2 timer is about the validity of the address that is offered, and
specifies how often that address should be renewed if the client accepts
the offer. The V6ONLY_WAIT timer is about how long the client should wait
before asking again if it doesn't accept the offer. I think these two could
be very different. For example, if IPv4 is a very scarce resource and
almost al clients are IPv6, the operator will want to use short lease times
(e.g., 1 hour, or shorter) to ensure that hosts that disconnect from the
network don't tie up scarce IPv4 addresses when they're not connected. That
same operator would want the V6ONLY_WAIT timer to be large in order to
avoid excessive load on the DHCP server (and to conserve battery on the
devices).

If there is consensus that this is useless we can remove it, but I don't
see a a strong reason to give up that extra flexibility. Is there?