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1、Networking ConceptNetworking Concept What is NetworkingWhat is Networking Networking is the sharing of information and services Computer networks includes computers and computer operating systems Computer networks are often classified by size, distance covered, or structure Network ClassificationNet
2、work Classification Local area network (LAN) Small group of connected computers 10Km Mbps Gbps Ethernet (10Mbps), Fast Ethernet (100 Mbps), Gigabit Ethernet (1000Mbps) Wide area network (WAN) Interconnect LANs Kbps Mbps Modem (33.6/56 kbps), X.25 (56 Kbps), Frame Relay (1.544 Mbps), T1 / E1 (1.544 M
3、bps), T3 / E3 (45 Mbps), ISDN 2B1D (64K),ATM (25 622 Mbps) File Server+Print Server Printer ( Printer buffer) HD( Queued ) Router WAN LAN Router LAN Required Network ElementsRequired Network Elements Three basic elements in Networking Something to share-Network Services A pathway of contacting other
4、s-Transmission media Rules for communication-Protocol Network ServicesNetwork Services Network services are provided by numerous combinations of computer hardware and software Service providers and requestors Servers-Only provide services Clients- Only request services Peers-Both Network ServicesNet
5、work Services File Services File transfer, file storage and data migration, File update synchronization Print services Share printers, queue print jobs Message services E-mail, workgroup applications Application services Run software for network clients Share processing power Database services Provi
6、de server-based database storage & retrieval function Replication Transmission MediaTransmission Media A method or pathway for contacting each other Cable media( twisted pair, coaxial, fiber optic cable) Wireless media (radio frequency, microwave, infrared) RJ45 connectorUnshielded Twisted Pair Cabl
7、e (UTP) (Core) (Cladding) (Protective Sheath) SC connectorLC connector Multi Mode 62.5/50 u core/ 125 u cladding Single Mode 8.3 u core/ 125 u cladding LC connector Connectivity DevicesConnectivity Devices Network connectivity devices Transmission media connectors Network Interface Card Modems Repea
8、ters Hubs Bridges Switches Internetwork connectivity devices Routers Brouters CSU/DSUs ProtocolProtocol Rules are required for communication between computer network devices Specific communication rules and rule sets are called protocols OSI Reference ModelOSI Reference Model 1977, ISO created the O
9、SI Reference Model, Functional guideline for dividing up communication tasks Network User OSI MODEL 7 Application layer Provides services to the application. Presentation layer Converts, encrypts data. Session layer Starts,stops session. Maintains order. Transport layer Ensures delivery of entire fi
10、le or message. Network layer Data Link (MAC) layer Transmits frames from node to node based on station address. Physical layer Passes information in bits across the connection medium. 6 5 4 3 2 1 Routes packets to LANs and WANs based on network address. Telnet , HTTP FTP , WWW etc JPEG , ASC EBCDIC
11、, GIFetc RPC , SQL NetBios namesetc TCP ,UDP ,SPX IP ,IPX , Apple Talk DDP 802.3/802.2 , HDLC etc EIA/TIA -232 , V.35 etc Physical LayerPhysical Layer Defines rules for transmitting bits of data Structure of a network (physical topology) Mechanical and electrical specifications for the transmission
12、medium Bit transmission encoding and timing rules Bits Data Link LayerData Link Layer Organizes bits into logical groups called frames Control information like source and destination addresses, frame length, and information about the upper layer protocols is added to the front end of the frame-heade
13、r Frame MAC Sub-layer Media access methods and logical topologies Addressing Data Link Sub-layer Frame synchronization Connection services Connectionless Non-reliable Error control Cyclic redundancy check (CRC) Network LayerNetwork Layer Organizing messages into logical groups called datagram packet
14、s Routing datagram packets to their correct destinations Connectionless services Connection-oriented services Transport LayerTransport Layer Provide end-to-end control and error-checking to determine if all the packets have arrived Reliability Session LayerSession Layer Connection services include c
15、onnection establishment, maintenance, and tear-down End-nodes exchange messages and agree to certain connection parameters, such as beginning sequence numbers and number of outstanding messages allowed Dialog Presentation LayerPresentation Layer Usually part of the OS and is responsible for formatting data Encrypt and translate received packets Format Application LayerApplication Layer Interface between user and computer Provides network services to the user Shared OSI Reference ModelOSI Reference Model N T S P A D Application Presentation Session Transport Ne
