Thanks to all of you who responded to my initial post regarding very rapid polling. I have fixed this particular instance with some cooperation from the ISP. However, the generic problem remains and is likely to re-appear. I don't know of a good general solution to this problem because:
1. the KOD packets are generally not effective. Either the remote software does not recognize them or it chooses to ignore them. The KOD method obviously would not work against an attack. 2. Sending any reply at all doubles the network traffic and makes an attack more effective. Therefore, all of the NIST servers log the event and the source ip but do not respond. I think it is not appropriate for a national timing laboratory to knowingly send the wrong time. 3. This sort of stuff is really more general than NTP -- denial of service attacks can use many different protocols and a more general network solution is going to be needed. 4. A serious denial-of-service attack probably requires a botnet to cause real trouble, and fixing that problem might reduce the impact of all denial of service attacks. Judah Levine Time and Frequency Division NIST Boulder _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
