plications, and networks together. Ethernet is the most common of these protocols. Other specialized protocols are used to access Storage Area Networks. www.TechnicalPDF.com The Ethernet Open Standard for Network Access Ethernet is an 802.3 open-standard protocol, approved by the Institute of Electrical and Electronics Engineers (IEEE), a non-profit standards body. Devices such as personal computers and printers use it to access the LAN and to retrieve packets from wired and wireless LANs. Each device on an Ethernet LAN has an address, referred to as its Media Access Control (MAC) address. Layer 2 switches in wiring closets use the MAC address to send messages to other LAN-attached devices. Ethernet is the first LAN access scheme that was widely adopted. Because it is based on an open standard, it is broadly available from different manufacturers. In the 1980s, departments within companies began to use Ethernet to link their computers together over coaxial cables to share software applications, such as accounting and financial tracking packages as well as printers. In the 1990s, lighter-weight, lower-cost unshielded, twisted- pair (UTP) cabling became available on new UTP cable standards on LANs. This greatly simplified installing and moving computers on LANs because of the lighter weight and flexibility of UTP cabling. See Table 2-2 for additional LAN protocols, devices and terms. Ethernet is an asynchronous protocol. Asynchronous protocols do not specify a specific start and stop time for each packet of data. All devices connected to the network attempt to send whenever they are ready. Ethernet's simplicity makes it straightforward to connect equipment to networks. All that's required are computers with Ethernet interfaces (ports) for an Ethernet cable, a Network Interface Card (NIC), and Ethernet software to link devices to switches in wiring closets. Because of the uncertainty of traffic volume at any given point in time, Ethernet networks are often configured to run at no more than half of their capacity. ww