Ethernet

Chapter 9

                        This chapter examines the characteristics and operation of the Ethernet as it has evolved from a shared media, contention-based data communications technology. This chapter will be able to describe the evolution of Ethernet, Explain the fields of the Ethernet frame, describe the physical and data link layer features of Ethernet, explain the address resolution protocol, Ethernet standards and implementation and IEEE standards. LAN is the original version of Ethernet.  The first Ethernet was published in 1980 by a consortium of Digital Equipment Corporation, Intel, and Xerox (DIX). The IEEE 802.2 standard describes the LLC sublayer functions and the 802.3 standard describes the MAC sublayer and the physical layer functions. The Logical Link Control (LLC) handles the communication between the upper layers and the networking software, and the lower layers. The LLC can be considered the driver software for the Network interface Card (NIC). NIC is a program that directly interacts with the hardware. The Ethernet MAC sublayer has two primary responsibilities which is Data Encapsulation, Media Access Control. In data encapsulation have three primary functions which is frame delimiting, addressing, and error detection. Data encapsulation provides for data link layer addressing. Media access controls the placement of frames on the media and the removal of frames from the media. Ethernet has evolved to meet the increased demand for high speed LANs. Ethernet specifies and implements encoding and decoding schemes that enable frame bits to be carried as signals across the media. The foundation for Ethernet technology was first established in 1970 with a program called Alohanet. Alohanet was a digital radio network designed to transmit information over a shared radio frequency between the Hawaiian Islands. Alohanet required all stations to follow a protocol in which an transmission required after a short period of waiting. The first versions of Ethernet used coaxial cable to connect computers in a bus topology. OSI data link layer physical addressing, implemented as an Ethernet MAC address, it is used to transport the frame across the local media. Ethernet LAN technology offers ethernet hubs to cater number of hosts connected to them on a LAN, but these two have different characteristics and features. Hubs and switches have the same function. Hub is an intermediary device where in multiple nodes can be connected to it in a shared media environment.