s including 3COM, Bay Networks (now Nortel Networks), Cisco Systems, Compaq, FORE Systems, Intel, Network Peripherals, Silicon Graphics and Sun Microsystems. The GEA's goal was to provide a low-cost and simple upgrade path for networks that already use Ethernet technology. The GEA presented their work to the IEEE, which formed the 802.3z Task Group to study the preliminary specification. On November 18, 1996, the 802.3z Task Group finalized a set of core proposals as the basis for writing the first draft of the standard. The first draft of the 802.3z specification was distributed in late January of 1997, and the standard was adopted in early 1998. Gigabit Ethernet is based on the 10Mbps and 100Mbps Ethernet standards outlined Packet-switched Networks in the 802.3 specification. It includes support for CSMA/CD (modifications must be made to maintain a half-duplex mode of operation) and uses the same frame format as Ethernet and Fast Ethernet. The first draft of the specification focuses primarily on physical media requirements. Gigabit Ethernet's physical (PHY) layer is a high-speed adaptation of Fiber Channel. An "Independent Interface" is also included in the draft that will allow the MAC protocol to be decoupled from the specifics of the lower layers-and thereby enable the independent development of other PHY types. Work is being done on adapting Gigabit Ethernet to operate over distances of up to 100 meters on unshielded twisted pair (UTP) cabling. Using LX (longwave length transceiver) GBICs and single-mode fiber, Gigabit Ethernet can span 5 kilometers with Gigabit Ethernet in 1999. Modifications to CSMA/CD include two new features that enable efficient operation over a practical collision domain diameter at 1000 Mbps. These features are carrier extension and packet bursting and they will only affect operation in half-duplex mode. When Gigabit Ethernet is operating in full-duplex mode, it is identical to 802.3u (100Base-T) Ethernet, only faster. The 802.3z specification includes minor MAC changes, but frame l