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

From: David Farmer <[email-masked]>
Date: Mon, 3 Jun 2019 13:08:31 -0500

On Tue, May 28, 2019 at 7:58 PM Mark Smith <[email-masked]> wrote:

> On Tue, 28 May 2019 at 22:53, David Farmer <[email-masked]> wrote:
> > Personally, I'm not particularly worried about DHCPDISCOVERS at least in
> most cases,
> > there are a few badly behaved clients, but in general exponential
> backoff in the client should deal with this nicely. Personally, my issue is
> IPv4 LL, in particular, service advertisement/discovery traffic using IPv4
> LL. This service advertisement/discovery traffic can be sizable and is
> already problematic for many WiFi networks so the elimination of such
> traffic that is by definition futile is an unqualified win in such
> situations.
>
> The thing about DHCPDISCOVERS is that they're a fundamental indicator
> of whether or not a host has IPv4 enabled or not.
>
> They're important here because if a host has stopped issuing
> DHCPDISCOVERS, then unless it has a manually configured IPv4 address,
> the host also won't be sending any other IPv4 traffic you mention.
> That means no sending of ARP DUD (ACD), mDNS, Netbios or any other
> IPv4 triggered link-layer broadcasts or multicasts.
>
> An IPv4 host without an IPv4 address has no need to use and is unable
> to use those other protocols. It is an IPv6 Only host now, rather than
> a Dual Stack host.
>

I'll note that by definition a dual-stack client has IPv4 enabled and it
should at least do initial DHCPDISCOVERS, unless it has a manually
configured IPv4 address. If it doesn't have IPv4 enable then it is an
IPv6-Only client, not a dual-stack client.  Also, for devices that are
mobile, disabling IPv4 on the client side is not practical at this time,
maybe someday it will be, but not until the vast majority of networks are
IPv6-only will disabling IPv4 in the client make any sense. So at this time
clients need to assume most networks are dual-stack.

However, as draft-ietf-6man-ipv6only-flag says, "hosts that support IPv4
and IPv6, usually called dual-stack hosts, need to also work efficiently on
IPv6-Only links."

Thank.

-- 
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