Re: IPv4 traffic on "ietf-v6ONLY"

Brian E Carpenter <brian.e.carpenter@gmail.com> Thu, 16 November 2017 00:56 UTC

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Subject: Re: IPv4 traffic on "ietf-v6ONLY"
To: David Farmer <farmer@umn.edu>
Cc: 6man WG <ipv6@ietf.org>
References: <f9805855-68cf-a3e8-a13f-c6ac31b09058@gmail.com> <bbd4e1d2-047f-6758-76f8-fd591c51dad7@gmail.com> <D631CE54.8C0F5%lee@asgard.org> <m1eEvEP-0000G3C@stereo.hq.phicoh.net> <D75288D5-B571-46EB-A35E-0DBD79F930E5@google.com> <72f42d56-2466-dfaa-59e9-ebb2264e8ca4@gmail.com> <CAN-Dau3mVnTKqkzYWHa3qnTHWWcos=BXKgGfKsyD9ScWAB4obA@mail.gmail.com>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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Date: Thu, 16 Nov 2017 13:56:36 +1300
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On 16/11/2017 13:39, David Farmer wrote:
> On Wed, Nov 15, 2017 at 5:54 PM, Brian E Carpenter <
> brian.e.carpenter@gmail.com> wrote:
> 
>> On 16/11/2017 08:15, james woodyatt wrote:
>>> On Nov 15, 2017, at 02:47, Philip Homburg <pch-ipv6-ietf-4@u-1.phicohcoh.
>> com> wrote:
>>>>
>>>> The safest option to do that is a DHCPv4 option that says 'no IPv4
>> service here, go away'.
>>>
>>>
>>> Better: extend ARP with a signal that says, “ARP is not welcome here."
>>
>> However, the IPv4 traffic seen on ietf-dns64 is negligible and harmless.
>> That is a practical indication that this problem probably isn't worth
>> solving.
>>
>> I submit for example that sending a new "not welcome" response to
>> ARP requests would do more harm than good, since the legacy hosts
>> would probably react badly.
>>
>>    Brian
>>
> 
> I'd love to see some data to back up the conjecture, that is the "traffic
> ... is negligible and harmless"

That it's negligible was shown in Bob Hinden's statistics from Wireshark.
That it's harmless seems obvious - it's virtually all multicast discovery
traffic that goes nowhere. As I said, I have a couple of capture files
if anybody is interested.

   Brian

> 
> I completely agree that "a new "not welcome" response to ARP requests would
> do more harm than good."
> 
> The problem I see is that WiFi airtime is precious, and worse yet broadcast
> packets (DHCPv4 discover and ARP) can use excessive airtime in some
> situations, more than the fraction of the bits they represent would
> indicate.  On a wired network I'm not all that worried, but on WiFi, I'd
> like some data on the matter.
> 
> On enterprise WiFi, you could filter ethertypes 0x0800 and 0x0806 at the
> AP, or they usually have DHCP and ARP proxies, either of which would
> prevent sleeping devices from being pestered by the traffic.  However, the
> traffic still consumes airtime and that's my concern, especially on large
> congested WiFi networks, like at IETF.
> 
> Thanks.
>