Re: New Version Notification for draft-hinden-ipv4flag-00.txt

Mikael Abrahamsson <swmike@swm.pp.se> Sun, 19 November 2017 14:53 UTC

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Date: Sun, 19 Nov 2017 15:53:48 +0100 (CET)
From: Mikael Abrahamsson <swmike@swm.pp.se>
To: Lorenzo Colitti <lorenzo@google.com>
cc: james woodyatt <jhw@google.com>, IPv6 List <ipv6@ietf.org>, Bob Hinden <bob.hinden@gmail.com>, Fernando Gont <fernando@gont.com.ar>
Subject: Re: New Version Notification for draft-hinden-ipv4flag-00.txt
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On Sat, 18 Nov 2017, Lorenzo Colitti wrote:

> Not sure how that would support IPv4 becoming available once the option 
> has been set. Also, not clear how to deal with the DOS scenario where a 
> rogue RA disables all IPv4 on the network until the end of time.

I think any "No IPv4"-flag would need to be just a hint to the hosts, and 
it would only be relevant to the router actually sending that RA.

So if your normal DHCPv4 "give up" time is X, then if this flag it set, 
shorten X to something much less?

The IPv6 specs say M=1 is a hint that tells the host that it might use 
DHCPv6 to acquire addresses if it so wants, right? Nothing says it can't 
do IA_NA request if M=0, and nothing says a host does the wrong thing if 
it doesn't do IA_NA request? I think this flag should be the same level of 
hint, and then the rest is up to the host implementation to do what it 
think is best.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se