An improved technique involves processing network traffic data to automatically establish whether a device on the network satisfies a particular set of constraints. Along these lines, a SIEM server observes and processes incoming and outgoing traffic data corresponding to a particular device at an address of the network. The SIEM server then analyzes this traffic data in order to determine whether the data satisfies a set of constraints satisfied by a client, or another set of constraints satisfied by a server. The SIEM server then applies the label of “client” or “server” to the device according to which set of constraints the SIEM server determines the data to have satisfied.