Ethernet extenders allow network communication over distances that exceed the limits described in IEEE (News - Alert) 802.3. Ethernet is a LAN protocol using a bus or star typology and supporting data transfer rates of 10 Mbps.

Suppliers of Ethernet extenders specify their products according to infrastructure type. Devices designed for fiber optic networks are suitable for point-to-point or multi-point configurations. Common features include built-in redundancy and daisy chain topology. Ethernet extenders can be used with LANs over two-wire or four-wire copper cable, synchronous optical network (SONET) architectures, as well as T1 or T3 lines. Ethernet extenders for copper cable are suitable for modem-to-modem connections over distances of up to 6 miles. Ethernet-over-SONET or packet-over-SONET products can cover greater distances and usually cost less than IP routers or asynchronous transfer mode (ATM) systems. Ethernet extenders designed for framed or unframed T1 and T3 lines help to maximize usage of IP addresses via remote management features. Sometimes, multiple T1 extensions over a fixed band can support distances of up to 50 miles.

Selecting an Ethernet extender requires an analysis of product specifications and approvals. These specifications include data rate, line coding, line interface, physical connection, protocol type, address aging, frame latency and frame buffer size. In the U.S., Ethernet extenders must conform to FCC regulations. In Europe, products bearing the CE Mark conform to EMC (News - Alert) directive 89/336/EEC and Low Voltage Directive 73/23/EEC. Ethernet extenders that bear marks from Underwriters Laboratory (UL) and the Canadian Standards Association (CSA) are also available.