UNICAST vs MULTICAST:

Most traffic on the Internet is IP Unicast.  Unicast involves a machine to machine or point-to-point communication.  IP Multicast is a point to muli-point communication protocol.  In the wireless classroom, the multimedia used by the teacher could include pictures or video clips that are over a megabyte in size along with audio feeds that require low variance and low packet loss.  This type of traffic places a heavy burden on the supporting network.  When Multicast is used instead of Unicast, the load on the network is reduced thereby improving the performance of the application software using the network.

Unfortunately most applications written for Windows 95 use Unicast communication.  Even collaborative applications like Databeam's Distance Learning Server and Teamwave's Collaborative Workplace use a centralized server and unicast communication and do not scale up to support live multimedia traffic.  Preloading slides and other multimedia data at the beginning of class can increase performance during class but often delayed the start of class and did nothing for live multimedia.  However, we did find a commercial product called  Lanscape  that uses multicasting, but we did not test its performance compared to other software.  We observed the best performance with the MBONE collaborative application suite because it supported IP multicast communication.  We typically used a whiteboard (wb), shared text editor (nt), video feed (vic), and audio feed (vat).  We were able to run all of these simultaneously with excellent performance.  Unfortunately, these tools were not developed for the wireless  classroom and often omitted features that would be useful in such a setting (see Software section).