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

["Bjoern A. Zeeb" <[e-mail]>]

On 10 May 2019, at 14:52, David Farmer wrote:

> I just had an additional thought, should there be any effect on a
> statically configured global scope unicast IPv4 address on a host in 
> the
> presence of this flag?
>
> This question got me thinking, the problem isn't really having an 
> address
> configured on the IPv4 stack or even having the IPv4 stack turned on, 
> the
> problem on the wire is IPv4 service discovery and too persistently 
> sending
> out periodic IPv4 DHCPDISCOVERS.
>
> So really the effect we needed is not necessarily a "hard off" for the 
> IPv4
> stack or even RFC 3927. If the IPv4 stack has an address on it, 
> statically
> configured or from RFC 3927, who cares. It is the generation of futile 
> IPv4
> service discovery traffic using that address and overly persistently
> periodic IPv4 DHCPDISCOVERS that is the issue for local battery and
> possibly WiFi airtime.
>
> Therefore, maybe what should be specified is a "hard off" for IPv4 
> service
> discovery in the presence of the flag and limiting IPv4 DHCPDISCOVERS. 
> Then
> note depending on the details of the IPv4 stack implementation the
> necessary effects can be achieved in several ways;
>
> 1. Turn off IPv4 service discovery and limit IPv4 DHCPDISCOVERS.
> 2. Do not configure an RFC 3927 address, if no IPv4 DHCPOFFER is 
> received
> and limit IPv4 DHCPDISCOVERS.
> 3. Turn off the IPv4 stack altogether.
>
> Noting that the list is in order of preference, but the particulars of 
> the
> IPv4 stack implementation will dictate the best solution in each
> implementation. Further, option #3 is NOT RECOMMENDED for especially 
> for
> general purpose hosts.


I like that thinking.  Keep going.

Here’s a suggestion.  If you were to implement your 1 or 2 or 3 what 
would you still see on your (IPv6 enabled) network if you’d run:

tcpdump -ln -e -s0 [-i <iface>] ipv4 or arp   (or use wireshark or 
equivalent).


Then, here’s the next question, using OSX as an example (you can do it 
on some other OSes in other ways):

networksetup -setv4off <networkservice>			(in the GUI: Configure IPv4: 
off)

and then run the tcpdump again.

Then think what you’d still see if all of that if all hosts would 
implement your 1/2/3?

Then repeat the same experiment on your unmanaged home network, your 
campus network, a coffee shop.


It’s enlightening :-)

/bz