Ethernet extenders permit network communication beyond the distance limitations laid out in IEEE 802.3 (News - Alert). Ethernet is a LAN protocol using a bus or star typology and supporting data transfer rates of 10 Mbps. There are also variations like Fast Ethernet and Gigabit Ethernet. Ethernet extenders are implement in conjunction with two kinds of Fast Ethernet: 100Base-X and 100Base-T. 100Base-X utilizes two physical links, one for transmission and one for reception, between nodes. 100Base-T utilizes medium access control protocol (MAC). Both support data transfers rates up to 100 Mbps. Ethernet extenders are also implemented in conjunction with Gigabit Ethernet, a high-speed LAN backbone that features speeds up to 1000 Mbps over single-mode or multi-mode fiber optic cable.
 

Ethernet extender suppliers specify products by infrastructure type. Devices intended for fiber optic networks are suitable for both point-to-point and multi-point configurations. Daisy chain topology and built-in redundancy are common features. Ethernet extenders can be combined with LANs over two-wire or four-wire copper cable, SONE) architectures, and either T1 or T3 lines. Ethernet extenders for copper cable are suitable for modem-to-modem connections at distances of up to 6 miles. Ethernet-over-SONET or packet-over-SONET products cover larger distances and tend to 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 the use of IP addresses by remote management features. Sometimes, multiple T1 extensions over a fixed band can support distances of up to 50 miles.

An analysis of product specifications and approvals are needed when selecting Ethernet extenders . Specifications include line coding, data rate, line interface, physical connection, address aging, protocol type, frame latency, and frame buffer size. In the U.S., Ethernet extenders conform to FCC regulations. In Europe, products with the CE Mark conform to EMC (News - Alert) directive 89/336/EEC and Low Voltage Directive 73/23/EEC. Ethernet extenders with marks from Underwriters Laboratory (UL) and the Canadian Standards Association (CSA) are available as well.

Brian Solomon is a Web Editor for TMCnet, covering news in the IP communications, call center and customer relationship management industries. To see more of his articles, please visit Brian Solomon’s columnist page.