Abstract: Methods and apparatus for extending the transmission range of a UTOPIA ATM (or packet) interface include providing two UTOPIA extension devices, one for coupling a PHY layer device to a transmission cloud and one for coupling an ATM layer (or LINK layer) device to the transmission cloud. Each device includes a UTOPIA interface emulator, a link controller, and a media transceiver. The media transceiver can be made to support various media such as a backplane, copper cable, optical fiber, or a wireless medium. The UTOPIA extension device preferably includes a UTOPIA inlet buffer, a UTOPIA outlet buffer, an inlet clock decoupling buffer, an outlet clock decoupling buffer, and a flow control module. The UTOPIA inlet and outlet buffers are used for traffic management and the clock decoupling buffers allow the UTOPIA interface emulator and the link controller to operate in different clock domains. The link controller provides error control and backpressure delivery to support flow control.