Ethernet Reading Answers

Ethernet is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1983 as IEEE 802.3. Ethernet has since been refined to support higher bit rates, a greater number of nodes, and longer link distances, but retains much backward compatibility. Over time, Ethernet has largely replaced competing wired LAN technologies such as Token Ring, FDDI and ARCNET. The original Ethernet uses coaxial cable as a shared medium, while the newer Ethernet variants use twisted pair and fibre optic links with switches. Over the course of its history, Ethernet data transfer rates have been increased from the original 2.94 megabits per second (Mbit/s) to the latest 400 gigabits per second (Gbit/s). The Ethernet standards comprise several wirings and signalling variants of the OSI physical layer in use with Ethernet. Systems communicating over Ethernet divide a stream of data into shorter pieces called frames. Each frame contains source and destination addresses, and error-checking data so that damaged frames can be detected and discarded; most often, higher-layer procedures trigger retransmission of absent frames. Per the OSI model, Ethernet provides services up to and including the data link layer. The 48-bit MAC address was adopted by other IEEE 802 networking standards, including IEEE 802.11 (Wi-Fi), as well as by FDDI. EtherType values are also used in Subnetwork Access Protocol (SNAP) headers. Ethernet is widely used in homes and industry and interworks well with wireless Wi-Fi technologies. The Internet Protocol is commonly carried over Ethernet and so it is considered one of the key technologies that make up the Internet. Ethernet has evolved to include higher bandwidth, improved medium access control methods, and different physical media. The coaxial cable was put in place of the point-to-point links connected by Ethernet repeaters or switches. Ethernet stations communicate by sending each other data packets: blocks of data individually sent and delivered. As with other IEEE 802 LANS, adapters come programmed with globally unique 48-bit MAC address so that each Ethernet station has a unique address. The MAC addresses are used to specify both the destination and the source of each data packet. Ethernet establishes link-level connections, which can be defined using both the destination and source addresses. On reception of a transmission, the receiver uses the destination address to determine whether the transmission is relevant to the station or should be ignored. A network interface normally does not accept packets addressed to other Ethernet stations.

An EtherType field in each frame is used by the operating system on the receiving station to select the appropriate protocol module (e.g., an Internet Protocol version such as IPv4). Ethernet frames are said to be self-identifying, because of the EtherType field. Self-identifying frames make it possible to intermix multiple protocols on the same physical network and allow a single computer to use multiple protocols together. Despite the evolution of Ethernet technology, all generations of Ethernet use the same frame formats, Mixed-speed networks can be built using Ethernet switches and repeaters supporting the desired Ethernet variants. Due to the ubiquity of Ethernet,

and the ever-decreasing cost of the hardware needed to support it, most manufacturers now build Ethernet

interfaces directly into PC motherboards, eliminating the need for a separate network card.