e-learining

Hi..

i want to build an e-learning application using c#.. it will contain video conference where all students see the teacher but the studends dont see the teahcer.. and the students can hear the teacher and the teacher can here the students if he allows him/her to talk..

any ideas where i should start and what i need to read about ,, please be specific.. not just tell me to read about the directX or directshow becuase they say nothing about video streaming over the internet.

thnx