What is dialog control at session layer of osi?

Dear Vikash,

Since Session layer is used to create, maintain and terminate sessions between client and server and also to differentiate multiple user sesssions among same or different servers. It is also responsible to identify the mode of the communication in a particular session between them like Simplex, Half Duplex or Full Duplex.

Simplex Sessions like - TV Broadcasting, Radio Broadcasting, etc

Half Duplex Sessions like - CB Radio (Police Wireless), Walkie Talkie, etc

Full Duplex Sessions like Telephone, Audio or Video Conferencing, etc

and that identification of mode of communication for a session is called Dialog Control

Thanks