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

[Lorenzo Colitti <[e-mail]>]

On Thu, Dec 5, 2019 at 10:24 PM <[e-mail]> wrote:

> Hosts do not do this today, and I don't think they will start doing so.
> The reason is that they cannot tell whether another protocol will start
> working. If they wait xxx ms to make sure the other protocol comes up, they
> are slowing down all connections to single-stack networks by xxx ms, making
> their users unhappy.
>
>
>
> *[Med] *Do you mean that clients that receive the signal to release IPv4
> configuration will make the users unhappy anyway because they will need to
> wait for the pref64 to properly work?
>

Well, that's the intent of the pref64 RA option. That allows the pref64 to
be communicated in the same packet as the rest of the configuration
parameters.


> Note that IPv6 has built-in delays in the protocol itself (DAD for the
> link-local address; various randomized delays) that make it very difficult
> to get anything done before at least 1-2 seconds have passed. Hosts that
> know that 70% of networks are IPv4-only will not want to wait 1-2 seconds
> to connect to those networks.
>
>
>
> [Med] In that case, what is the benefit for the host to indicate its
> ipv6-only mode support?
>

The option improves the situation by allowing the host to wait for IPv6
only if it is expected to exist. Hosts that implement the option allow
networks to provide better service and create an incentive for networks to
support IPv6, which is good for everybody in the long term.