Proxy mobile IP provides mobility to a mobile device that is not equipped to perform client mobile IP by moving the mobile IP signaling responsibility from the mobile device into the network. A network element performs the mobile IP signaling on behalf of the mobile device. In one scenario, the mobile device establishes a PPP session with a foreign agent, with no mobile IP signaling on top of the PPP session. The foreign agent then performs mobile IP signaling with the mobile device's home agent to negotiate a proxy mobile IP session for the device. Once the session registration lifetime has been established by the foreign agent and the home agent, the foreign agent communicates the registration lifetime to the mobile device by way of a PPP vendor-specific packet.