Multicast is a set of technologies that enables efficient delivery of data to many locations on a network. In today’s Internet, the dominant model of communication is “unicast”—the data source must create a separate copy of the data for each recipient. When there are many recipients, and when large amounts of data (e.g. streaming video) are being sent, unicast becomes prohibitively wasteful of bandwidth. The key idea behind multicast is to create each recipient's copy of each message at a point as close to that recipient as possible, thus minimizing the bandwidth consumed. In July 2007, MAGPI worked with the Friends of Live Earth Global Screens Program to send out a 30 mbps webstream of the 24-hour Live Earth Concert to campuses and organizations on the MAGPI and Internet2 networks, as well as other research and education networks worldwide. Northwestern University and Video Furnace, in collaboration with C-SPAN and Internet2, make live, high-quality C-SPAN and C-SPAN2 broadcasts [PDF] available 24 hours a day to anyone with an Internet2 network connection that is multicast capable.