Patent ID: 8923311

Claim:
A unit for use at a terminal as an external wireless modem, the unit comprising: first interface apparatus comprising a first wireless transceiver for connecting via a wireless cellular network to a gateway between the wireless cellular network and a further, packet-based network; second interface apparatus for connecting to the terminal; and processing apparatus configured to perform operations of a wireless cellular modem so as to enable the terminal to access the further network via the wireless cellular network and gateway; wherein the processing apparatus is arranged to receive a first link layer identifier from one of the wireless cellular network, the gateway and the further network, intended for use by the terminal as a source identifier when accessing the further network via the wireless cellular network and gateway; and wherein the processing apparatus is configured to intercept at least one message being conveyed from the terminal to the gateway comprising a second link layer identifier generated by the terminal as a source identifier, to translate the second identifier into the first link layer identifier, and to retransmit the message to the gateway with the first link layer identifier as the source identifier.