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

james woodyatt <jhw@google.com> Mon, 27 November 2017 20:14 UTC

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From: james woodyatt <jhw@google.com>
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Subject: Re: New Version Notification for draft-hinden-ipv4flag-00.txt
Date: Mon, 27 Nov 2017 12:14:16 -0800
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Cc: IPv6 List <ipv6@ietf.org>
To: Jen Linkova <furry13@gmail.com>
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On Nov 18, 2017, at 06:39, Jen Linkova <furry13@gmail.com>; wrote:
> 
> It looks to me that when you are saying 'there is no IPv4 support on a link' you mean 'a router does not provide IPv4 connectivity'.  However it still might be IPv4 connectivity within the given broadcast domain and the router has nothing to do with it.

Indeed, and this is an important to distinction to bear in mind. I hope everyone involved in this discussion remembers it.

> If the problem is 'IPv4 broadcast noise on the link' then it should be solved on L2 level and the network should not switch ethertype 0x0800.

Better would be not to switch Ether Type 0x806 when the PTYPE=0x800. Or it should reject configuration via IPCP. Or or or...

> If the problem is 'all those noisy DHCPv4 requests the first-hop router has to drop because DHCP relay is not configured' then the router interface should not accept IPv4 packets at all, problem solved.


If the problem is noisy hosts using IPv4 group communication for mDNS and DHCP discovery, then the problem is the same as “IPv4 broadcast noise on the link” and it should be handled the same way.

If you want to stop link-local IPv4 communication on the link, the right way to do that is by blocking ARP with PTYPE=0x800, and probably some kind of ARP packet that specifically tells IPv4 implementations that this network will never deliver an ARP packet with PTYPE=0x800 to a host so it can stop trying.

If you want to stop noisy hosts trying to reach Internet via IPv4 via an unprovisioned route, then the right way to tell them to shut them up is to decline DHCP requests for IPv4 default router address, and tell host operating system developers that when the only DHCP server on the link is declining to configure any IPv4 default router address, it’s not a misconfiguration: the network really means it, there is no default IPv4 router. (In the PPP case, provide only an IPv4 link-local address.)


--james woodyatt <jhw@google.com <mailto:jhw@google.com>>