Thousand of A.ROOT-SERVERS.NET domain in my queries

I have an Android Phone that connect on both wifi home/office, but even when the phone is off the request are still in the log.
With the tail log, there is a pattern on the requests every 30 seconds, the ip 79.18.84.144 is the external ip assigned to the router from the adsl provider.
Maybe it is the Router TpLink calling home?