Based on these and other considerations, Gigabit Ethernet (GbE) has been selected as the backbone communications technology for NEPTUNE. Ethernet is the most widely used data networking technology in the world, and has 10 and 100 Mbit/s standards in addition to a high data rate capability. GbE routing and switching hardware is readily available from many vendors. Standard converters are also available with the ability to drive 100 km or more of single mode optical fiber. This permits GbE hardware to serve the dual functions of a data concentrator/router and an optical fiber repeater, eliminating the need for optical amplifiers. This yields long haul 1 Gb/s full duplex communications using a pair of optical fibers. Higher data rates are feasible using multiple fiber pairs; the NEPTUNE goal of a 10 Gb/s backbone could be met by ten pairs of fibers. Each NEPTUNE node will contain a pair of GbE routers for redundancy.