1. A method of transmitting a data stream among a node set comprising a source of the data stream and a set of receivers over a routing tree set, respective routing trees specifying a route of the data stream among the source and the receivers, the method comprising: representing the node set as a primal model allocating a routing tree data rate of the data stream for respective routing trees, the routing tree data rate within a capacity of respective nodes and within a capacity of respective connections between nodes in the route of the routing tree; selecting routing tree data rates for respective routing trees that increase an aggregated data rate according to the primal model; apportioning data substreams of the data stream for respective routing trees according to the routing tree data rate of the routing tree; and transmitting the data substreams over the respective routing trees at the respective routing tree data rates.