MPEG 2 is the type of video you want to get today. In distance learning, there are various different technologies. For example, there are the E Series, the J Series, Analog, ISDN, and MPEG2. For example, an E Series to ISDN Gateway is one type of gateway. Unicast is transmission from one source to one destination.
Broadcast is transmission from one source to all destinations.
Multicast is transmission to a subset of multiple destinations. IGMPv2 is in draft right now. See also the ATM section in Chapter 4. ATM was made, in part, for video distribution, and it does it very well.