1. A method, comprising: receiving a data aggregator discovery (DAD) message at a particular node in a directed acyclic graph (DAG) of a computer network, the DAD message initiated by a data aggregator identified in the DAD message, the DAD message comprising a recorded route taken from the data aggregator to the particular node as well as a total path cost for the particular node to reach a root node of the DAG through the recorded route and via the data aggregator; determining a path cost increase (PCI) associated with use of the data aggregator based on the total path cost within DAD message as compared to a DAG-based path cost for the particular node to reach the root node via the DAG; and redirecting traffic from the particular node to the data aggregator in response to the PCI being below a configured threshold, the traffic redirected as source-routed traffic according to the recorded route in the DAD message.