IP multicast
Mbone was free and it used a network of routers that support IP multicast, and it enables access to real-time interactive multimedia on the Internet. Many older routers do not support IP multicast. To cope with this, tunnels must be set up on both ends: multicast packets are encapsulated in unicast packets and sent through a tunnel. Mbone uses a small subset of the class D IP address space (224.0.0.0–239.255.255.255) assigned for multicast traffic. Mbone uses 224.2.0.0 for multimedia conferencing.