Re: problem statement [was Re: New Version Notification for draft-hinden-ipv4flag-00.txt]

Brian E Carpenter <brian.e.carpenter@gmail.com> Wed, 22 November 2017 00:15 UTC

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Subject: Re: problem statement [was Re: New Version Notification for draft-hinden-ipv4flag-00.txt]
To: Nick Hilliard <nick@foobar.org>, Lorenzo Colitti <lorenzo@google.com>
Cc: IETF IPv6 Mailing List <ipv6@ietf.org>
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From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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Date: Wed, 22 Nov 2017 13:15:02 +1300
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On 22/11/2017 11:33, Nick Hilliard wrote:
> Lorenzo Colitti wrote:
>> On Wed, Nov 22, 2017 at 12:47 AM, Nick Hilliard <nick@foobar.org>; wrote:
>>> There would also be a requirement
>>> for the network edge to be able to filter out RAs with this option,
>>
>> Why is it not sufficient to configure the routers that emit the RAs?
> 
> because you're assuming congruity between ipv4 and ipv6 connectivity on
> a network, which is not codified in any ietf document that I'm aware of.
>  If there is a incongruity between management of the two protocols, then
> the l2 network must have a mechanism to stop an ipv6 gateway from
> attempting shutting down ipv4 services.

This is a very interesting point. If every IPv6 router on a link believes
there is no IPv4 router/DHCP service, they would all send flag==1 in the
proposed solution. So the proposal only works if at least one IPv6 router
is colocated with an IPv4 router, and therefore knows to send flag==0.
Oops.

   Brian