Facebook do have access to Skype via Microsoft. I do not know so much about Flash Multicast but this is not IP multicast, right? it is more like: Application L

Facebook do have access to Skype via Microsoft. I do not know so much about Flash Multicast but this is not IP multicast, right? it is more like: Application Layer Multicast which is peer-to-peer but like a star or mesh or tree type of topology. If Airtime is one person talking to another it does not really need multicast but just be peer to peer. However, if it is similar to hangouts then at some point (or at some degree of users in a chat room) you'll need to introduce a central server or need a tree type of topology to distribute video (especially when users have asymmetric uplink and downlink throughputs).