Yamaha mLAN Manual Book page 12

Technical Explanations
Figure 5
The above diagrams show the frequently-used tiered star (multiple stars that are connected) as a
tree structure. In a tree structure, nodes that are not connected to another node in the direction
away from the root are called "leaf nodes." In the above diagrams, these nodes are shown in
gray.
Since IEEE 1394 treats all topologies as tree structures, a specific node will automatically be
selected as the root node. (It is also possible for the user to specify a specific node as the root.)
In order to transfer realtime data such as audio and MIDI, the clocks that are built into each device
to measure data timing must be synchronized; i.e., the devices must be synchronized. The node
containing the clock used as the master is called the "cycle master," and the root node fulfills this
role.
The cycle master node is indispensable when transferring realtime data such as audio and MIDI. If
the power of the cycle master node is turned off, or if the cable is disconnected from it, it will no
longer be possible to transfer data. Consequently, the sound will be interrupted. If this occurs
another node will be selected as the root node, and data transfer will resume.
By using IEEE 1394 compatible extending and relaying devices, bus connections can be branched
and extended in an efficient manner. Such devices are collectively called "repeaters."
Of the different types of topology, "loops" cannot be interpreted as a type of tree; thus, it is not
permitted to create a loop within the topology.
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Tiered star
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Root 4
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Tree structure
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Loops
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