Re: [Ntp] Antw: [EXT] Re: WGLC on draft‑ietf‑alternative‑port‑01

Danny Mayer <mayer@pdmconsulting.net> Sat, 31 July 2021 22:33 UTC

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To: Watson Ladd <watsonbladd@gmail.com>
Cc: Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de>, Miroslav Lichvar <mlichvar@redhat.com>, Dieter Sibold <dsibold.ietf@gmail.com>, NTP WG <ntp@ietf.org>
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From: Danny Mayer <mayer@pdmconsulting.net>
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Date: Sat, 31 Jul 2021 18:33:13 -0400
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On 7/31/21 12:59 PM, Watson Ladd wrote:
> On Thu, Jul 29, 2021, 12:12 PM Danny Mayer <mayer@pdmconsulting.net> wrote:
>>
>> On 7/29/21 11:01 AM, Watson Ladd wrote:
>>> On Thu, Jul 29, 2021, 12:45 AM Ulrich Windl
>>> <Ulrich.Windl@rz.uni-regensburg.de> wrote:
>>> <snip>
>>>>>> We see issues at Cloudflare with packet delivery on port 123. ISP
>>>>>> middleboxes are going to police by length, and an alternative port is
>>>>>> the way forward. There is much less policing on the alternative ports.
>>>>> Actually I'd think teching cloudflare would be better than changing the
>>>> I had meant to write "teaching"...
>>> It's not our devices: it's middleboxes in ISP networks. We only find
>>> out from customer pcaps where one in four NTS packets makes it
>>> through. The policing is by length because that is what these boxes
>>> support.
>>>
>> So how would using an alternative port make a difference?
> The other port is not policed now. We use it, and take care to not
> massively deploy amplifiers on it, so it does not get policed.  This
> issue is not about opening firewalls that are under people's control.
> This is about firewalls on ISP networks to protect the ability of the
> network to function, that break and do things like take NIST offline
> in the Western US for a month.
>
> Sincerely,
> Watson

If you are not policing privileged ports then you have a problem with 
your firewall.

Danny