Internet Home networking.ppt
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1、1,Internet & Home networking,Prof. J. Won-Ki Hong jwkhongpostech.ac.krDept. of Computer Science & Engineering POSTECH,2,Contents,Data Communication NetworkInternet & World Wide WebHome Networking,3,Data Communication Network,4,1960s “How can we transmit bits across a communication medium efficiently
2、 and reliably?”1970s “How can we transmit packets across a communication medium efficiently and reliably?”1980s “How can we provide communication services across a series of interconnected networks?,Brief History of Computer Networks,5,1990s “How can we provide high-speed, broadband communication se
3、rvices to support high-performance computing and multimedia applications across the globe?”2000s What do you think will dominate in the next 10 years?,6,A Communication Model,7,Common Communication Tasks,Data encoding: the process of transforming input data or signals into signals that can be transm
4、ittedSignal generation: generating appropriate electro-magnetic signals to be transmitted over a transmission mediumSynchronization: timing of signals between the transmitter and receiver ; when a signal begins and when it ends; duration of each signal,8,Error detection and correction: ensuring that
5、 transmission errors are detected and correctedFlow control: ensuring that the source does not overwhelm the destination by sending data faster than the receiver can handleMultiplexing: a technique used to make more efficient use of a transmission facility. This technique is used at different levels
6、 of communication,9,Addressing: indicating the identity of the intended destination Routing: selecting appropriate paths for data being transmitted Message formatting: conforming to the appropriate format of the message to be exchanged Security: ensuring secure message transmission Systems managemen
7、t: configuring the system, monitoring its status, reacting to failures and overloads, and planning for future growth,10,Communication Network,A communication network is a collection of devices connected by some communications mediaExample devices are: mainframes, minicomputers, supercomputers workst
8、ations, personal computers printers, disk servers, robots X-terminals Gateways, switches, routers, bridges Cellular phone, Pager, TRS Refrigerator, Television, Video Tape Recorder,11,Communications Media twisted pairs coaxial cables line-of-sight transmission: lasers, infra-red, microwave, radio sat
9、ellite links fiber optics Power line,12,Network Structures,Point-to-Point Networks each communication line connects a pair of nodes a packet (or message) is transmitted from one node to another intermediate nodes, in general, receive and store entire packet and then forward to the next node also cal
10、led “store-and-forward” or “pack-switched” some topologies: star, ring, tree,13,Broadcast Networkshave a single communication line shared by all computers on the network packets sent by a host are received by all computers some topologies: bus, satellite, radio,14,Types of Communication Networks,Loc
11、al Area Networks (LANs) a few km high data transmission rate (at least several Mbps) ownership usually by a single organization e. g., Ethernet, IBM Token Ring, Token Bus, FDDI, Fast Ethernet, ATM, Gigabit Ethernet,15,POSTECH LAN (1998.6),16,POSTECH LAN (1999. 3),17,Metropolitan Area Networks (MANs)
12、up to 50 km fibre optics is a popular technology for MANs may be private or public may involve a number of organizations e.g., cable TV networks (CATV), ATM networks,18,Wide Area Networks (WANs)a few km to thousands of km point-to-point networks (also called long-haul networks) lower data transmissi
13、on rate than LANs fiber optics is a popular technology for MANs ownership usually by more than a single organization e.g., ARPANET, MILNET (US military), CA*NET, NSFNET, KREONET, BoraNet, KORNET, INET, Internet,19,Internet in Korea (1995.5),20,Internet in Korea (1999.6),21,Growth of Internet Users i
14、n Korea,22,Growth of Internet Hosts in Korea,23,Computer Communication Architecture,Computer Communication the exchange of information between computers for the purpose of cooperative actionComputer Network a collection of computers interconnected via a communication network,24,Protocol agreement re
15、quired between the communication entities and consists of three components: Syntax: data format and signal levels Semantics: control information for coordination and error handling Timing: speed matching and sequencingCommunications Architecture a structured set of modules that implements the commun
16、ication function,25,ISO-OSI Reference Model,International Standards Organization (ISO) Open Systems Interconnection (OSI) Reference model is a framework for connecting computers on a networkMotivation? to reduce the complexity of networking software as a step towards international standardization of
17、 the various protocols,26,The main principles applied to the OSI layered architecture are each layer represents a layer of abstraction, each performs a set of well-defined functions, implementation of a layer should not affect adjacent layers, and inter-layer communication should be minimized,27,App
18、lication,Presentation,Session,Transport,Network,Data Link,Physical,OSI Stack,Application,Presentation,Session,Transport,Network,Data Link,Physical,OSI Stack,Application,Presentation,Session,Transport,Network,Data Link,Physical,OSI Stack,28,Functions of the OSI Layers 1. Physical layer responsible fo
19、r the electro-mechanical interface to the communications media 2. Data link layer responsible for transmission, framing and error control over a single communications link. 3. Network layer responsible for data transfer across the network, independent of both the media comprising the underlying subn
20、etworks and the topology of those subnetworks.,29,4. Transport layer responsible for reliability and multiplexing of data transfer across the network (over and above that provided by the network layer) to the level required by the application. 5. Session layer responsible for establishing, and manag
21、ing sessions between cooperating applications. 6. Presentation layer responsible for providing independence to the application process from differences in data representation (syntax). 7. Application layer ultimately responsible for managing the communications between applications.,30,How Communicat
22、ion Takes Place Between the Layerscommunication takes place between peer entities.a layer provides services to the layer above it.services are available at SAPs (Service Access Points) analogous to telephone numbers and street addresses,31,32,On the sending side: a layer receives a PDU (Protocol Dat
23、a Unit) from the layer above it, with some ICI (Interface Control Information) (such as address, data size, etc.). the layer ads some PCI (Protocol control Information) to the APDU and passes the enlarged PDU to the layer below along with more ICI. A layer may also fragment a PDU into several smalle
24、r pieces to be passed separately to the layer below (in this case, the peer entity at the receiving end will reassemble the fragments).,33,At the receiving end: a layer receives a PDU from the layer below. The layer strips off the PCI added by its peer, and passes the PDU to the layer above it. If t
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