A method, device, and computer-readable storage element enables a multi-mode device to establish a session through multiple networks in a communication system. The method includes registering, at the same time, each of a plurality of sub-clients of a single multi-mode device with a single application server, wherein each sub-client is separately registered through a different network, using an individual logical identity. The method further includes detecting an invitation including session parameters to establish a session using the single application server, and selecting at least one of the sub-clients to process the invitation based on the session parameters to establish the session through the networks corresponding to the selected sub-client.