講義說明第一天

1、Building a Simple Network Understanding EthernetLocal Area NetworkLAN ComponentsComputersPCsServersInterconnectionsNICsMediaNetwork devicesHubsSwitchesRoutersProtocolsEthernetIPARPDHCPFunctions of a LANData and applicationsShare resourcesProvide communication path to other networksLAN SizesEthernet

2、EvolutionLAN StandardsCSMA/CDEthernet Frame StructureCommunicating Within the LANMAC Address ComponentsMAC AddressesSummaryA LAN is a network that is located in a limited area, with the computers and other components that are part of this network located relatively close together. Regardless of its

3、size, several fundamental components are required for the operation of a LAN, including computers, interconnections, network devices, and protocols.LANs provide both communication and resource-sharing functions for their users.LANs can be configured in various sizes, to modate environments from SOHO

4、 to enterprise.Summary (Cont.)Ethernet was originally developed in the 1970s by DEC, Intel, and Xerox, and was called DIX Ethernet. When a workgroup of this body (referred to as IEEE 802.3) defined new standards for Ethernet in the mid-1980s to define Ethernet-like networks for public use, the stand

5、ards were called Ethernet 802.3 and 802.2.Ethernet LAN standards specify cabling and signaling at both the physical and data link layers of the OSI model.Stations on a CSMA/CD LAN can access the network at any time. Before sending data, CSMA/CD stations listen to the network to determine whether it

6、is already in use. If it is in use, they wait. If the network is not in use, the stations transmit. A collision occurs when two stations listen for network traffic, hear none, and transmit simultaneously.Summary (Cont.)An Ethernet frame consists of fields, including preamble, start-of-frame delimite

7、r, destination address, source address, type/length, data and pad, and frame check sequence.There are three major kinds of communications in networks: unicast, in which a frame is sent from one host addressed to one specific destination; broadcast, in which a frame is sent from one address to all other addresses; and multicast, in which a destination addresses a specific group of devices.The address used in an Ethernet LAN is the means by which data is directed to the proper receiving location. Summary (Cont.)The MAC sublayer