Computer Networks

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Information about Computer Networks
Education

Published on February 3, 2010

Author: aSGuest37322

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Slide 1: Computer Networks Introduction Zaka Ul-Mustafa Zaka-mcs@nust.edu.pk Faculty offices, Old telecom building. Office timings: During “Student Teacher Interaction” Text Book : Text Book Computer Networks (Fourth edition) By Andrew S. Tanenbaum Data Communication and Networking: by Fourouzan For reference books, see course handout. Course Goals : Course Goals Fundamental understanding of the network architecture and how to provide application requirements Cover core as well as newer networking technologies Goal is to cover as much breadth rather than depth As much hands on experience as possible Quantitative approach Home work projects should help Course policies : Course policies Course organization and expectation Grading policy Final: 50% Midterm 30% Quizzes & Assignments 20% late policy None – Projects/homework/critiques are due at right before the beginning of class. I do not accept late submissions. Please contact me regarding unforeseen emergencies Academic honesty Plagiarism may not be tolerated. DATA COMMUNICATION : DATA COMMUNICATION Communication and Telecommunication. Data Communication---------- Exchange of 0s and 1s. Data Communication --------- Local; Remote Effective Data Communication: (Fundamental characteristics) a) Delivery-------- correct destination b) Accuracy------- correct data c) Timeliness----- Same order; No significant delay Block Diagram of a communication System : Block Diagram of a communication System Components : Components Data or Massage Sender Receiver Link or Medium or communication Channel Protocol Network Applications : Network Applications Marketing and Sales Financial Services Manufacturing Electronic Messaging Directory Services Information Services Electronic Data Interchange Teleconferencing Cellular TelePhone Cable Television Uses of Computer Networks : Uses of Computer Networks Business Applications Home Applications Mobile Users Social Issues Business Applications of Networks : Business Applications of Networks A network with two clients and one server. Resource Sharing………… & Client Server Model Business Applications of Networks (2) : Business Applications of Networks (2) The client-server model involves requests and replies. Slide 12: Strong Communication. Emails, video conferencing Manufacturing Processes Inventory control E-commerce Home Network Applications : Home Network Applications Access to remote information (hobbies, newspapers) Person-to-person communication Interactive entertainment Electronic commerce Slide 14: Mobile user Social issues (e.g privacy issues,) Home Network Applications (3) : Home Network Applications (3) Some forms of e-commerce. PROTOCOLS : PROTOCOLS Merely sending the bit stream from one node to another and expecting a proper communication to occur ! Life is not that simple!!! Protocol defines: What is communicated; how it is communicated and When it is communicated. STANDARDS : STANDARDS There are many factors needed to be synchronized. Why standards are necessary?(Competitive Market) Two types of standards: a) De facto (By Fact) b)De Jure (By Law) i) Proprietary (closed standards) ii) Nonproprietary (Open standards;Developed by groups or committees) De Jure Standards : De Jure Standards De jure standards are those ratified by recognized international standards bodies such as the ISO and IEEE. Ethernet is an example of a de jure standard De facto standards : De facto standards de facto standards usually result from a standards battle in the market where dominance is achieved by being first, being bigger, being better or having more marketing clout. But standards battles can also be won by second to market, smaller, inferior products and standards. The Sony Playstation was second to market after Sega Those which aren’t necessarily open or based on any de jure standards. DOS is an example of a de facto standard.     At a time when it mattered, there were three distinct DOS products on the market: MS-DOS from Microsoft, PC DOS from IBM, and DR DOS from Digital Research. Although they were similar products with similar features, each had its own quirks which meant you could never be 100 per cent certain your software would run on them all. Standards and Organizations : Standards and Organizations Standards are developed by cooperation between: Standards Creation committees, forums and government agencies Standards Creation Committees: a) ISO(International standards Organization,1947,82 members) Provides models for Compatibility, improved Quality, increased productivity decreased prices) b) ITU-T (International Telecommunication Union-Telecommunication Standards Sector) United nation developed CCIIT. Two popular standards developed by ITU are V series and X series. c) IEEE It sponsored an important project for local area network called ‘Project 802’ Forums : Forums To accommodate the need of working models, agreements and to facilitate the process of standardization. Forum works with universities and users to test evaluate and standardize new technologies. Internet Society (ISOC) and Internet Engineering Task Force(IETF) ISOC concentrates on user issues, including enhancement to the TCP/IP protocol suit. IETF reviewa internet software and hardware. e.g SNMP (Simple Network Management Protocol) Regulatory Agencies : Regulatory Agencies All communication Technologies require approval from Government Agencies The purpose of these agencies is to protect people interest by regulating radio and Wireless communication IN Pakistan: PTA (Pakistan Telecom Authority) In America: FCC Network Hardware : Network Hardware Local Area Networks Metropolitan Area Networks Wide Area Networks Wireless Networks Home Networks Internetworks Broadcast Networks : Broadcast Networks Types of transmission technology Broadcast links Point-to-point links Metropolitan Area Networks : Metropolitan Area Networks A metropolitan area network based on cable TV. Wide Area Networks : Wide Area Networks Relation between hosts on LANs and the subnet. Wide Area Networks (2) : Wide Area Networks (2) A stream of packets from sender to receiver. Broadcast Networks : Broadcast Networks Types of transmission technology Broadcast links By a specific bit pattern in address field Multicast, one bit for indicating multicast transmission other n-1 bits for group address. Point-to-point links Also called Unicasting Broadcast Networks (2) : Broadcast Networks (2) Classification of interconnected processors by scale. Types of Networks : Types of Networks There are three different ways in which we classify the networks Organizational Point of View Geographical Point of View Computing Point of View Organizational Point of View : Organizational Point of View From organizational point of view, networks are divided into two types Peer-to-Peer Server based Peer-to-Peer : Peer-to-Peer These are also called Workgroups. A peer-to-peer network comprises of 10 or less users and is suitable for small-sized business organizations. In this model of networking the resources are randomly scattered on the network with every machine acting as a server as well as client Server Based networks : Server Based networks They are sometimes referred to as Domains. This is a centralized model of networking with resources placed on a dedicated machine called Server. There is no user limit as such, as it depends directly on your hardware resources and capacity to support users. Geographical Point of View : Geographical Point of View From geographical point of view, there are three types of networks. LAN WAN MAN/CAN LAN or Local Area Network : LAN or Local Area Network A LAN encompasses a small area such as a floor or a building with all the machines connected directly via the same medium generally. Slide 36: LANs may be characterized by: their size Their transmission technology Their topology Local Area Networks : Local Area Networks Two broadcast networks (a) Bus (b) Ring Arbitration may be centralized or distributed Channel allocation may be static (e.g round robin) or dynamic (centralized or decentralized). Slide 40: Local Area Network Some more topologies : Some more topologies Mesh: How many cables and I/O ports are needed? Advantages & disadvantages Star: Hub…………. As a repeater, active Hubs, passive Hubs. Advantages Less cables as compared to ? In case of a single link failure Easy Fault Identification Disadvantages Reletively more cables ……………. Tree topology Hybrid topology. Mesh topology : Mesh topology WAN or Wide Area Network : WAN or Wide Area Network A WAN comprises of a very large physical area that covers countries and continents. Internet is one good example of a WAN. The machines in a WAN are connected through different mediums and protocols. Generally, the Dial-up-Networks are used for this purpose. Slide 44: Wide Area Network Wide Area Networks : Wide Area Networks Relation between hosts on LANs and the subnet. Host: Machines for running user programs. Wide Area Networks (2) : Wide Area Networks (2) A stream of packets from sender to receiver. STORE & FORWARD MAN (Metropolitan Area Network)or CAN (Campus Area Network) : MAN (Metropolitan Area Network)or CAN (Campus Area Network) A MAN is almost similar to a WAN except that a MAN only encompasses an area that is within a city. CAN is a campus area Network which is used with in a campus for the sharing of resources. Computing Point of View : Computing Point of View Networks are divided into two types from the point of view of computing. Centralized Networks Client-Server Networks Centralized Networks : Centralized Networks The centralized networks rely totally on one dedicated machine called server for all the processing and computing and the clients or the terminals act as dumb entities. If the client requires a certain set of data, whole of the data set is transferred at the client end, which also is wastage of the network bandwidth. Client-Server Networks : Client-Server Networks In this model of networking, only the required set of data is returned to the client while both the server and the client take part in the processing or computing of the queries. This is a more efficient way of processing and is hence applied generally more than the centralized method, nowadays. . Wireless Networks (2) : Wireless Networks (2) (a) Bluetooth configuration (b) Wireless LAN Wireless Networks (3) : Wireless Networks (3) (a) Individual mobile computers (b) A flying LAN Network Software : Network Software Layers ……. To reduce complexity Shielding, data encapsulation Peer layers Protocol…. The agreement between layers and parties. Interfaces No data is directly communicated between two layers Protocol stack Network architecture………. Set of layers and protocols. Dessign issues : Dessign issues Addressing Error control Flow control Multiplexing Routing

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