Very similar traffic pattern can be seen here: 
http://lx.ujf.cas.cz/ntp-lx/lx-pkt.html.
The time is CET=GMT+1 at those graphs. I guess that there are clients who 
see the leap second flag but are unable to make this jump on its own. They 
lurk only for the right moment.

Karel Sandler

> From: "Nelson Minar" <[email protected]>

>I just noticed an interesting traffic pattern on my pool server's logs: 
> NTP traffic went up a huge amount right before the transition to January 
> 1, 2009. You can see the change here:  
> http://www.somebits.com/ntp/one%20month.html
> 
> Requests / second went up from my usual 25 to nearly 300, a 12x increase.
> 
> Some of the traffic may be new clients (I see a 3x spike in unique IPs), 
> but a lot of it looks like existing clients sending more requests. 
> Usually a single IP sends an average of 3 requests / 10 minutes, but 
> during the spike interval it goes to 9 requests / 10 minutes, for a 3x 
> increase. It's possible that's actually new clients sharing IP addresses 
> of a NAT router.
> 
> The oddest thing is the duration of the spike. I'd expect it to be a 
> brief spike around 00:00 Jan 1 UTC as clients flubbed the leap second. 
> But in fact the increase starts almost two days before and peaks several 
> hours before 00:00.
> 
> Any guesses what happened? Did other pool servers see the same spike? I 
> have more data that could be analyzed if someone's really excited.
> 
> PS: the pool server monitor thinks my offset was below 10ms most of the 
> time over this time period.
> 
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