数据教程课件chapter1introductiontocsp

1、1,Chapter One,Introduction to Communications, Standards and Protocols,2,Introduction,Who today has not used a computer network? Mass transit, interstate highways, 24-hour bankers, grocery stores, cable television, cell phones, businesses and schools, and retail outlets support some form of computer

2、network,Chapter One - Introduction to Communications, Standards, And Protocol,3,The Language of Computer Networks,Computer network an interconnection of computers and computing equipment using either wires or radio waves over small or large geographic areas Local area network networks that are small

3、 in geographic size spanning a room, floor, building, or campus,Chapter One - Introduction to Communications, Standards, And Protocol,4,The Language of Computer Networks,Metropolitan area network networks that serve an area of 1 to 30 miles, approximately the size of a typical city Wide area network

4、 a large network that encompasses parts of states, multiple states, countries, and the world,Chapter One - Introduction to Communications, Standards, And Protocol,5,The Language of Computer Networks,Personal area network a network of a few meters, between wireless devices such as PDAs, laptops, and

5、similar devices Voice network a network that transmits telephone signals Data network a network that transmits computer data,Chapter One - Introduction to Communications, Standards, And Protocol,6,The Language of Computer Networks,Data communications the transfer of digital or analog data using digi

6、tal or analog signals Telecommunications the study of telephones and the systems that transmit telephone signals Network management the design, installation, and support of a network, including its hardware and software,Chapter One - Introduction to Communications, Standards, And Protocol,7,The Big

7、Picture,Networks are composed of many devices, including: Workstations (computers, telephones) Servers Network hubs and switches (bridges) Routers (LAN to WAN and WAN to WAN) Telephone switching gear,Chapter One - Introduction to Communications, Standards, And Protocol,8,Chapter One - Introduction t

8、o Communications, Standards, And Protocol,9,Topologies,Common Bus Topology Star Topology Ring Topology Fully Connected Topology Combined Topologies,Chapter One - Introduction to Communications, Standards, And Protocol,10,LAN Topologies,11,Common Bus Topology,Multipoint medium: contention Transmissio

9、n propagates throughout medium Heard by all stations Need to identify target station Each station has unique address Full duplex connection between station and tap Allows for transmission and reception Need to regulate transmission To avoid collisions Terminator absorbs frames at end of medium,12,Fr

10、ame Transmissionon Bus LAN,13,Star Topology,Each station connected directly to central node Usually via two point to point links Central node can broadcast Physical star, logical bus Only one station can transmit at a time Central node can act as frame switch,14,Ring Topology,Repeaters joined by poi

11、nt to point links in closed loop Receive data on one link and retransmit on another Links unidirectional or bidirectional Stations attach to repeaters Data in frames Circulate past all stations Destination recognizes address and copies frame Frame circulates back to source where it is removed Media

12、access control determines when station can insert frame( token passing for example),15,Frame TransmissionRing LAN,16,Ring and Star Usage,Ring Very high speed links over long distances Single link or repeater failure disables network Star Best for short distances High data rates for small number of d

13、evices,17,Combined Topology,Fully Connected Topology,18,Need For Standards,Task broken into subtasks Implemented separately in layers in stack Functions needed in both systems Peer layers communicate,Types of Standards,De facto standards Formally recognized and adopted by a standards organization,19

14、,Key Elements of a Protocol,Syntax Data formats Signal levels Semantics Control information Error handling Timing Speed matching,20,Standards Organizations,ITU: International Telecommunications Union, formerly called CCITT. ITU-T X.25 IETF: Internet Engineering Task Force IEEE: Institute of Electric

15、al and Electronic Engineer, the largest professional organization,Three models to learn OSI model, Internet layers and TCP/IP protocol suite,21,Organization of air travel,a series of steps,WHY LAYERING？,22,Layering of airline functionality,Layers: each layer implements a service via its own internal

16、-layer actions relying on services provided by layer below,23,Dealing with complex systems: explicit structure allows identification, relationship of complex systems pieces layered reference model for discussion modularization eases maintenance, updating of system,WHY LAYERING？,24,Overview of the OS

17、I model:,Chapter One - Introduction to Communications, Standards, And Protocol,25,Application layer where the application using the network resides. Common network applications include web browsing, e-mail, , and remote logins Presentation layer performs a series of miscellaneous functions necessary

18、 for presenting the data package properly to the sender or receiver,Chapter One - Introduction to Communications, Standards, And Protocol,26,Network Architectures - OSI,Session layer responsible for establishing sessions between users Transport layer provides an end-to-end error-free network connect

19、ion. Makes sure the data arrives at the destination exactly as it left the source. Network layer responsible for creating, maintaining and ending network connections. Transfers a data packet from node to node within the network.,Chapter One - Introduction to Communications, Standards, And Protocol,2

20、7,Network Architectures - OSI,Data link layer responsible for taking the data and transforming it into a frame with header, control and address information, and error detection code Physical layer handles the transmission of bits over a communications channel. Includes voltage levels, connectors, me

21、dia choice, modulation techniques,Chapter One - Introduction to Communications, Standards, And Protocol,28,Logical and physical connections,Chapter One - Introduction to Communications, Standards, And Protocol,29,Network Architectures,Logical and physical connections A logical connection is one that

22、 exists only in the software, while a physical connection is one that exists in the hardware Note that in a network architecture, only the lowest layer contains the physical connection, while are higher layers contain logical connections,Chapter One - Introduction to Communications, Standards, And P

23、rotocol,30,Chapter One - Introduction to Communications, Standards, And Protocol,31,The OSI Environment,32,Connection Strategies: Circuit Switching: phones Message Switching: store and forward networks Packet Switching: Datagram Virtual Circuit Table 1.2,Chapter One - Introduction to Communications,

24、 Standards, And Protocol,33,OSI Layers (1),Physical Layer Physical interface between devices Mechanical Electrical Functional Procedural,34,OSI Layers (2),Data Link Layer Error detection and correction Parity Bit (even/odd) Media Access Control CSMA/CD Token Passing Token Ring Token Bus Flow Control

25、,35,OSI Layers (3),Network Layer Transport Layer Follow Control Connection Management Exchange of data between end systems Session Control of dialogues between applications Difference from the transport layer connection,36,OSI Layers (4),Presentation Layer Code Conversion Data Compression Encryption Application Layer Protocol Web Browing E-mail ,37,Internet Layers,application: supporting network applications FTP, SMTP, STTP transport: host-host data transfer TCP, UDP network: routing of datagrams from source to destination IP, routing protocols link: data transfer between neighboring netwo