I believe Apple has an agreement with Akamai. Here are some data points for just one household with two macs, two iPhones, and two iPads
www.isg-apple.com.akadns.net 571 requests in the last day
us-courier.push-apple.com.akadns.net 558 requests in the last day
.akamai.net 709 requests in the last day
and
.akamaiedge.net 1967 requests in the last day
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I believe Google just uses *.l.google.com (my open dns says 1202 requests in the last day)