The disclosure pertains to methods and apparatus for supporting multiple application IDs on a single unicast link using Layer-3 Relay. Methods and apparatus for operation by a wireless transmit/receive unit (WTRU) are provided. In an embodiment, a method may include any of receiving a first request message to establish a direct communication with a peer WTRU, the request message including an indication of first user information of the peer WTRU, associated with a first application and/or a first application identity; transmitting, to the peer WTRU, information indicating a first Internet Protocol (IP) address; receiving a second request message to associate a second application with the direct communication; transmitting a second response message including a second IP address; and communicating, with the peer WTRU using the direct communication, data related to the first application using the first IP address and data related to the second application using the second IP address.