Associating service agents in communication over a network to one or more respective clients coupled to the network at respective ports of the network is described. At a first service agent, a first signal is received from a first client coupled to the network at a first port. The first signal propagates over a first signal propagation path between the first service agent and the first port. An association between the first service agent and the first client is established based at least in part on a difference between: the first signal propagation path between the first service agent and the first port, and a second signal propagation path between the first service agent and a second port or between a second service agent and the first port.