Re: Confirmation to advance: draft-ietf-6man-ipv6only-flag-05

[Lorenzo Colitti <[e-mail]>]

>
> I.e. if you want actual management, then you need to manage, and that
> mandates enforcement.  The larger your network, the more effort you need
> to put into designing it properly - and managing it using appropriate
> equipment.
>

I think you're forgetting the case where the network is managed and the
devices are not (e.g., BYOD on enterprise networks). This flag is a perfect
fit for such networks.

The network administrator can, as you say, manage: drop all IPv4 frames,
use L2 ACLs, whatever they want to do. But even if the administrator does
all that, the host has no way of knowing that this network has no IPv4 *by
design*, as opposed to a network that is experiencing an IPv4-only outage,
or because the host's DHCPv4 packets all got unlucky and got taken out by
cosmic rays, or...

On such a network, the flag provides a good way to tell the host: we don't
support IPv4 on this network. The host can trust that or not. If it does,
it can save battery power for its users and reduce airtime impact by
disabling DHCPv4 or retransmitting DHCPv4 less frequently, disabling
features like IPv4 MDNS, etc. etc.