Difference between BIGIP-LTM and BIG-IP GTM

This is my hypothesis .. correct me if I'm wrong _/\_

 

 

Assume GTM1 is at DC1 & GTM2 is at DC2

 

When Local DNS ask for "www.example.com" IP at GTM1 (by Default DC) ... GTM 1 in DC 1 will talk with GTM 2 in DC 2 by WAN or else with protocol iQuery.

 

to see which data center was performing best. If DC2 is best then GTM 1 will answer Local DNS with A record of "www.example.com" of DC 2