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

[Brian E Carpenter <[e-mail]>]

On 11-May-19 08:08, Mikael Abrahamsson wrote:
> On Fri, 10 May 2019, 神明達哉 wrote:
> 
>>> "   A host that receives only RAs with the flag set to 1 SHOULD NOT
>>>     attempt any IPv4 operations, unless it subsequently receives at least
>>>     one RA with the flag set to zero.  As soon as such an RA is received,
>>>     IPv4 operations MAY be started.
>>> "
>>
>> This text doesn't read to me that "a host SHOULD NOT start IPv4
>> operations until it has received an RA with the ipv6only-flag
>> cleared".  At least literally, it just talks about the host's behavior
>> *after* it receives an RA with ipv6only-flag on.
> 
> Some people seems to have read "attempt" in the above text as "should not 
> start", meaning it should delay starting IPv4 operations until it knows 
> about the status of this flag (the host has no idea about the flag status 
> until it has received RAs at attach time).
> 
> If we don't want this to happen then the current text in -05 is not clear 
> enough on this case. I believe several people have voiced their opinion 
> that they would accept the flag being part of the heuristic of deciding 
> whether to continue doing DHCPv4 and/or IPv4 LL (or not). The -05 text 
> doesn't seem to actually say this, so it should be changed?

It's always been my opinion that the flag is input to a heuristic; but
from time to time we've had pushback asking for it to be more definitive.

Since I'm remarkably bad at predicting the future, despite much practice,
I really don't know what will be the right heuristic ten or twenty years
from now.

(The Google statistics were up to 28.02% IPv6 on May 4th. The future seems
to be getting closer.)

    Brian