Ethernet is the most popular local area network (LAN) technology implemented worldwide. Ethernet was first developed in early 1970s. Basically, Ethernet includes a shared transmission medium such as a twisted pair cable or co-axial cable and a multi-port hub, bridge or switch. Computers, printers and workstations are connected to each other through the hub/switch/bridge using the cables in a star-like or a bus-like configuration.

General features of Ethernet are summarized as follow:

• Shared media: all network devices on the network take turns to use the same share media for communication
• Broadcast domain: transmitted frames are sent to all nodes but only the node addressed shall receive the frames.
• CSMA/CD: Ethernet uses the Carrier Sense Multiple access/Collision Detection method to prevent twp or more nodes from sending at the same time.
• MAC address: All Ethernet Network Interface Card (NIC) uses a 48-bit network address at the Media Access Control layer. The address is globally unique.

Basic Ethernet networking components:

• Share medium and cables: 10BaseT (Twisted-Pair), 10Base-2(Coaxial Thinnet), 10Base-5(Coaxial Thick cable0
• Repeater or Hub: The Hub or repeater is a device that accepts numerous Ethernet connections from network devices and cross connects them. Data arriving via the receive pair of one connection is regenerated and sent out on the transmit pair to all connected devices except for the device who originated the transmission.
• Bridge: A bridge is a layer-2 device that divides a network into separate collision domains or segments while keeping the broadcast and sharing feature within the same domain/segment. The bridge keeps a table of all segments and forward frames properly to make sure communication within or across segments are conducted smoothly.
• Switch: Switch, like a bridge, is a layer 2 and multi-port device. Switch provides similar functions as a bridge but has more advanced features that can temporarily connect any two ports together. It contains a switch matrix or switch fabric that can rapidly connect and disconnect ports. Unlike Hub, a switch only forward frame from one port to the other port where the destination node is connected without broadcast to all other ports.

The Ethernet protocols: The Ethernet frame structure is defined by IEEE 802.3. Currently four data rates are defined for operation over optical fiber and twisted-pair cables for Ethernet networks:

• 10 Mbps – 10Base-T Ethernet (802.3)
• 100 Mbps – Fast Ethernet (802.3u)
• 1000 Mbps – Gigabit Ethernet (802.3z)
• 10 Gigabit Ethernet – IEEE 802.3ae

Ethernet Overview

Related Terms: Hub, Switch, Bridge, Ethernet Protocols, CSMA/CD, MAC address

Reference Links:
http://www.cpcstech.com/ethernet-information.htm: Ethernet Overview
http://www.javvin.com/protocolEthernet.html: Ethernet: IEEE 802.3 Local Area Network (LAN) protocols