EtherLoop, sometimes called next generation DSL or second generation DSL, combines features of Digital Subscriber Line (DSL) with features of Ethernet to provide both voice and data transmission (including Internet connection) over any ordinary phone line at data rates faster than DSL. EtherLoop offers a data transfer rate up to 6 Mbps over distances of up to 21,000 feet.
Developed by Nortel, EtherLoop, unlike DSL, uses the half-duplex transmission of Ethernet. Because half-duplex transmission is less susceptible to certain kinds of interference from adjacent lines and devices such as bridge taps, existing phone lines can be used without special conditioning or replacement. Unlike Ethernet and like DSL, transmission is point-to-point which means that connection speed is not decreased while multiple users are sharing the same path. Because transmission is point-to-point, at any given time one device can be designated as the server and the other the client. The server decides when the client can transmit, so collisions (which are a problem with Ethernet) can be avoided. Like Ethernet, EtherLoop operates in a burst transmission mode. Packets are sent in bursts, according to demand. EtherLoop uses the idle time between bursts to monitor performance, check for problems, and select alternate paths when necessary.
Jack Terry, then with Nortel, initiated the EtherLoop project in 1996. Terry's goal was to create a telco-based technology that would be competitive with cable for the high-speed market. To this end, EtherLoop was designed to take advantage of existing resources in a more efficient manner. Because voice traffic only uses a small portion of the bandwidth in regular phone wire, about a megahertz (MHz) of available bandwidth is available for data. EtherLoop is suitable for a broad range of applications, including local area network (LAN) extensions, hotels, campus area networks, as well as residential and corporate Internet access.