Q: Why am I being DoS attacked by Apple?

I've a Netgear router with DoS protection enabled and inside the logs I read:

[DoS Attack: Ascend Kill] from source: 17.253.54.253, port 123, Wednesday, January 06, 2016 15:50:17
[DoS Attack: Ascend Kill] from source: 17.253.54.251, port 123, Wednesday, January 06, 2016 15:50:17
[DoS Attack: Ascend Kill] from source: 17.253.52.125, port 123, Wednesday, January 06, 2016 15:50:17
[DoS Attack: TCP/UDP Echo] from source: 17.253.4.253, port 123, Wednesday, January 06, 2016 15:49:01

Doing a WhoIs on these IPs I get:

IP Location United States United States New York City Apple Inc.
ASN United States AS6185 APPLE-AUSTIN - Apple Inc. (registered Dec 21, 1995)
Resolve Host nlams2-ntp-001.aaplimg.com

So, now the question is:

Why is Apple trying to DoS me?