MBONE: Multicasting Tomorrow's Internet
Typically, audio is carried at 32 or 64 kb/s, video at up to 128 kb/s. Other services such as imm and sd need very small amounts of bandwidth.
Note that the design bandwidth must be multiplied by the number of tunnels passing over any given link since each tunnel carries a separate copy of each packet. This is why the fanout of each mrouted node should be no more than 5-10 and the topology should be designed so that at most 1 or 2 tunnels flow over any T1 line.
While most MBONE nodes should connect with lines of at least T1 speed, it will be possible to carry restricted traffic over slower speed lines. Each tunnel has an associated threshold against which the packet's IP time-to-live (TTL) value is compared. By convention in the IETF multicasts, higher bandwidth sources such as video transmit with a smaller TTL so they can be blocked while lower bandwidth sources such as compressed audio are allowed through.
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