A client device comprises: (a) a memory, (b) an application program, and (c) a signal processing configuration. The memory is configured and arranged to facilitate a connection of the client device with a target device over a secure communication link created based on (i) an address request generated by the client device, and (ii) a determination as a result of the address request that the target device is a device with which a secure communication link can be established when the requested address is identified in an address lookup. The application program is configured and arranged so as to allow participation in audio/video communications with the target device over the secure communication link once the secure communication link is established. The signal processing configuration is arranged to execute the application program.