The controller sends {HEAD ~ a notification} to the agent when the file updates are retrieved, and the agent retrieves {TAIL ~ the file} updates from the controller 
The controller sends { HEAD ~ a notification } to the agent when the file updates are retrieved , and the agent retrieves { TAIL ~ the file } updates from the controller
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH