In general, the disclosure describes a method that includes partitioning resources of a computing device into a first namespace comprising a first physical network interface and a second namespace comprising a second physical network interface; creating, by a test agent executing as a process in the second namespace, a test agent child in the second namespace; migrating the test agent to execute as a process in the first namespace; communicating, by the test agent child via the second physical network interface, test packets; obtaining, by the test agent, network performance measurement data that is based at least on the test packets; and outputting, by the test agent while executing as a process in the first namespace, an indication of the network performance measurement data.