Filter NTP traffic by packet size?

Blake Hudson blake at
Tue Feb 25 16:58:00 UTC 2014

I talked to one of our upstream IP transit providers and was able to 
negotiate individual policing levels on NTP, DNS, SNMP, and Chargen by 
UDP port within our aggregate policer. As mentioned, the legitimate 
traffic levels of these services are near 0. We gave each service many 
times the amount to satisfy subscribers, but not enough to overwhelm 
network links during an attack.


Chris Laffin wrote the following on 2/23/2014 8:58 AM:
> Ive talked to some major peering exchanges and they refuse to take any action. Possibly if the requests come from many peering participants it will be taken more seriously?
>> On Feb 22, 2014, at 19:23, "Peter Phaal" <peter.phaal at> wrote:
>> Brocade demonstrated how peering exchanges can selectively filter
>> large NTP reflection flows using the sFlow monitoring and hybrid port
>> OpenFlow capabilities of their MLXe switches at last week's Network
>> Field Day event.
>>> On Sat, Feb 22, 2014 at 4:43 PM, Chris Laffin <claffin at> wrote:
>>> Has anyone talked about policing ntp everywhere. Normal traffic levels are extremely low but the ddos traffic is very high. It would be really cool if peering exchanges could police ntp on their connected members.
>>>> On Feb 22, 2014, at 8:05, "Paul Ferguson" <fergdawgster at> wrote:
>>>> Hash: SHA256
>>>>>> On 2/22/2014 7:06 AM, Nick Hilliard wrote:
>>>>>> On 22/02/2014 09:07, Cb B wrote:
>>>>>> Summary IETF response:  The problem i described is already solved
>>>>>> by bcp38, nothing to see here, carry on with UDP
>>>>> udp is here to stay.  Denying this is no more useful than trying to
>>>>> push the tide back with a teaspoon.
>>>> Yes, udp is here to stay, and I quote Randy Bush on this, "I encourage
>>>> my competitors to block udp."  :-p
>>>> - - ferg
>>>> - --
>>>> Paul Ferguson
>>>> VP Threat Intelligence, IID
>>>> PGP Public Key ID: 0x54DC85B2
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