A communication transaction or use case is broken down into constituent
parts, one of which can be provided, at the direction of a master service
node, from the master service node or primary service path and the other
of which can be provided from a support service node or secondary service
path that the client station might happen to be able to communicate with.
For instance, the base layer of a multimedia stream might be provided
from the master node, but if its bandwidth becomes full, an enhancement
layer of the stream can be provided by the support node, as directed by
the master node.