In one embodiment, a device determines that input data to a machine learning model sent from a plurality of source nodes to an aggregation node is causing network congestion. A set of one or more other nodes to perform aggregation of the machine learning model input data is selected. A type of aggregation to be performed by the set of one or more other nodes is also selected. The set of one or more other nodes is also instructed to perform the selected type of aggregation on the data sent from the source nodes.