I want to know which device initiates the data exchange in OSPF protocol (master device or slave device).
From "OSPF version 2" RFC 2328
During the Hello phase, every router sends packets:
Hello packets are sent periodically out all router interfaces. (section 7.1)
During database synchronisation, the master leads:
Database Description Packets sent by the master (polls) are acknowledged by the slave (section 7.2)