1. How the traffic initiated with respect to @McAfee Threat Intelligence Exchange server and agent?
2. Do we have any option to modify the communication interval of agent and TIE server ?
3. One DXL Hub handles how many agents at a time ?
Well there is no interval as all participants are listening to the bus. As soon as there is info applied to it you get it. So it´s "nearyl" realtime.
An interval like in the Agent-Server-Communication-Interval is not given here.
Currently no idea on how much clients one DXL server can handle but I would suggest you to read the manuals.