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Introduction to Computer Networks: Business, Home, and Mobile Applications

This chapter provides an overview of computer networks and their uses in various contexts, including business, home, and mobile applications. It covers topics such as the client-server model, peer-to-peer systems, e-commerce, network hardware, broadcast networks, wireless networks, and internetworks.

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Introduction to Computer Networks: Business, Home, and Mobile Applications

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  1. Introduction Chapter 1

  2. Uses of Computer Networks • Business Applications • Home Applications • Mobile Users • Social Issues

  3. Business Applications of Networks • A network with two clients and one server.

  4. Business Applications of Networks (2) • The client-server model involves requests and replies.

  5. Home Network Applications • Access to remote information • Person-to-person communication • Interactive entertainment • Electronic commerce

  6. Home Network Applications (2) • In peer-to-peer system there are no fixed clients and servers.

  7. Home Network Applications (3) • Some forms of e-commerce.

  8. Mobile Network Users • Combinations of wireless networks and mobile computing.

  9. Network Hardware • Local Area Networks • Metropolitan Area Networks • Wide Area Networks • Wireless Networks • Home Networks • Internetworks

  10. Broadcast Networks • Types of transmission technology • Broadcast links • Point-to-point links

  11. Broadcast Networks (2) • Classification of interconnected processors by scale.

  12. Local Area Networks • Two broadcast networks • (a) Bus • (b) Ring

  13. Broadcast Network • Static and Dynamic • Static – Divide time into discrete intervals, • - Use Round Robin • Disadvantage - wastes channel capacity • Dynamic Allocation • Centralized or Decentralized • Centralized – A Bus Arbitration Unit • Decentralized – No central entity, each machine decides for itself

  14. Metropolitan Area Networks • A metropolitan area network based on cable TV.

  15. Wide Area Networks • Relation between hosts on LANs and the subnet.

  16. Wide Area Network • Subnet • Transmission Lines – move bits between machines • Switching Elements – Connect three or more transmission lines • Router • Subnet – Collection of Communication Lines and Routers • Different from Subnet ip

  17. Wide Area Networks (2) • A stream of packets from sender to receiver.

  18. Wide Area Network • Store and Forward or Packet-Switched • When a packet is sent from one router to the other via one or more intermediate router in its entirety, stored there until the required output is free. • Message divided into packets • Satellite connection

  19. Wireless Networks • Categories of wireless networks: • System interconnection • Wireless LANs • Wireless WANs

  20. Wireless Networks (2) • Bluetooth configuration Master Slave Paradigm – Master tells the slave what address to use what frequency they can use and when they can broadcast

  21. Wireless Networks (3) Wireless LAN – 802.11 • (a) Individual mobile computers • (b) A flying LAN

  22. Wireless WAN • 3G Cellular Network – both voice and data (low-speed network)

  23. Home Network Categories • Computers (desktop PC, PDA, shared peripherals • Entertainment (TV, DVD, VCR, camera, stereo, MP3) • Telecomm (telephone, cell phone, intercom, fax) • Appliances (microwave, fridge, clock, furnace, airco) • Telemetry (utility meter, burglar alarm, babycam).

  24. Features of Home Network • Network and devices have to be easy to install • Read the Manual • Reboot the computer • Remove all the hardware and software except ours and try again • Download Newest driver • Reformat the harddisk • Networks and Devices have to be foolproof in operation • (no big manuals) • Low Price (will pay a little extra atmost)

  25. Features of Home Network • Main application is likely to involve multimedia, so the network needs sufficient capacity • Possible to start out with one or two devices and expand the reach • Security and reliability will be very important • Burglars disarm ones security

  26. Internetworks • Some LANS connected through WANS • Distinct networks are connected

  27. Network Software • Protocol Hierarchies • Design Issues for the Layers • Connection-Oriented and Connectionless Services • Service Primitives • The Relationship of Services to Protocols

  28. Network SoftwareProtocol Hierarchies • Layers, protocols, and interfaces.

  29. Protocol Hierarchies (2) • The philosopher-translator-secretary architecture.

  30. Protocol Hierarchies (3) • Example information flow supporting virtual communication in layer 5.

  31. Design Issues for the Layers • Addressing • Error Control • Flow Control • Multiplexing • Routing

  32. Connection-Oriented and Connectionless Services • Connection – oriented (telephonic system) • Sender, receiver and subnet needs to have a negotiation about the parameters to be used such as maximum message size, quality of services required and other issues • Connection-less (postal service) • Quality of Service

  33. Connection-Oriented and Connectionless Services • Six different types of service.

  34. Service Primitives Listen – server, Connect – client to server and then connection is established • Five service primitives for implementing a simple connection-oriented service.

  35. Service Primitives (2) • Packets sent in a simple client-server interaction on a connection-oriented network.

  36. Difficulties • Unreliable networks • Synchronization problem

  37. Services to Protocols Relationship Service – Abstract Data Type or an object in an object-oriented language • The relationship between a service and a protocol.

  38. Reference Models • The OSI Reference Model • The TCP/IP Reference Model • A Comparison of OSI and TCP/IP • A Critique of the OSI Model and Protocols • A Critique of the TCP/IP Reference Model

  39. A layer is created where a different abstraction is needed • Each layer should perform a well-defined function • The function of each layer should be chosen with an eye toward defining internationally standardized protocols • The layer boundary should be chosen to minimize the information flow across interfaces • The number of layers should be large enough that distinct functions need not be thrown together out of necessity and small enough that the architecture does not become unweildy

  40. Reference Models The OSI reference model.

  41. Physical Layer (questions) • How many volts should be used to represent 1 • How many nanoseconds a bit lasts • Transmission may proceed in one direction or multiple direction • How intitial connection established • How many pins the network connector has

  42. DataLink • Raw transmission facility in a line that appears free of undetected errors to the network layer. • Data frames  acknowledgement frame

  43. Reference Models (2) • The TCP/IP reference model.

  44. Reference Models (3) • Protocols and networks in the TCP/IP model initially.

  45. IP – Packet Switching • Transport Layer – TCP – Flow control • UDP – Fast Delivery

  46. Comparing OSI and TCP/IP Models • Concepts central to the OSI model • Services • Interfaces • Protocols • TCP – retrofit/ • OSI – DataLink Layer (point-to-point)

  47. Differences between OSI and TCP/IP model • OSI model supports connectionless and connection-oriented communication in the network layer but only connection-oriented communication in the transport layer • TCP/IP model has one mode in the network layer (connectionless) but supports both modes in the transport layer

  48. A Critique of the OSI Model and Protocols • Why OSI did not take over the world • Bad timing • Bad technology • Bad implementations • Bad politics

  49. Bad Timing • The apocalypse of the two elephants. (Standard came much later)

  50. Bad Implementation • Initial version were huge, unwieldy and slow. • Bad Politics • TCP/IP part of Unix, OSI – governement pushed

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