A wireless device comprising: a radio for communicating via a wireless communication protocol which employs messages constructed as layer 2 MAC frames each including a layer 2 MAC header and a payload, an electronic chip programmed to configure the wireless device to: operate in (i) a first mode in which the wireless device transmits messages (N0,..., Nn) via the radio to a relay device each including an IPv6 packet header and an upper layer protocol data unit encapsulated within the payload of a layer 2 MAC frame and (ii) a second mode in which the wireless device transmits messages (M0,..., Mn) via the radio to the relay device each including an upper layer protocol data unit encapsulated within the payload of a layer 2 MAC frame without including the IPv6 header; and transition from the first mode to the second mode by operations including transmitting a header information message via the radio to the relay device which provides a header insertion service, the header information message including at least an address of the wireless device to be used to construct an IPv6 source address or an address of a host device to be used to construct an IPv6 destination address, and wherein the transition from the first mode to the second mode is by operations further including receiving a message from the relay device which triggers the transition from the first mode to the second mode, the message being arranged to inform the wireless device of availability of the relay device to perform the header insertion service for the wireless device. a radio for communicating via a wireless communication protocol which employs messages constructed as layer 2 MAC frames each including a layer 2 MAC header and a payload, an electronic chip programmed to configure the wireless device to: operate in (i) a first mode in which the wireless device transmits messages (N0,..., Nn) via the radio to a relay device each including an IPv6 packet header and an upper layer protocol data unit encapsulated within the payload of a layer 2 MAC frame and (ii) a second mode in which the wireless device transmits messages (M0,..., Mn) via the radio to the relay device each including an upper layer protocol data unit encapsulated within the payload of a layer 2 MAC frame without including the IPv6 header; and transition from the first mode to the second mode by operations including transmitting a header information message via the radio to the relay device which provides a header insertion service, the header information message including at least an address of the wireless device to be used to construct an IPv6 source address or an address of a host device to be used to construct an IPv6 destination address, and wherein the transition from the first mode to the second mode is by operations further including receiving a message from the relay device which triggers the transition from the first mode to the second mode, the message being arranged to inform the wireless device of availability of the relay device to perform the header insertion service for the wireless device. operate in (i) a first mode in which the wireless device transmits messages (N0,..., Nn) via the radio to a relay device each including an IPv6 packet header and an upper layer protocol data unit encapsulated within the payload of a layer 2 MAC frame and (ii) a second mode in which the wireless device transmits messages (M0,..., Mn) via the radio to the relay device each including an upper layer protocol data unit encapsulated within the payload of a layer 2 MAC frame without including the IPv6 header; and transition from the first mode to the second mode by operations including transmitting a header information message via the radio to the relay device which provides a header insertion service, the header information message including at least an address of the wireless device to be used to construct an IPv6 source address or an address of a host device to be used to construct an IPv6 destination address, and wherein the transition from the first mode to the second mode is by operations further including receiving a message from the relay device which triggers the transition from the first mode to the second mode, the message being arranged to inform the wireless device of availability of the relay device to perform the header insertion service for the wireless device.