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Aleksandra Smiljani ć aleks@ieee

Aleksandra Smiljani ć aleks@ieee.org. Introduction. Uses of Computer Networks. Business Applications Home Applications. Business Applications. Sharing resources Common databases for customer records, inventory, accounts E-commerce Video-conferencing

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Aleksandra Smiljani ć aleks@ieee

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  1. Aleksandra Smiljanićaleks@ieee.org Introduction

  2. Uses of Computer Networks • Business Applications • Home Applications

  3. Business Applications • Sharing resources • Common databases for customer records, inventory, accounts • E-commerce • Video-conferencing • Disseminating the information, and coordination

  4. Home Applications • Getting the remote information • Person-to-person information • E-commerce • Entertainment • E-flea

  5. Network Types • Local Area Networks • Metropolitan Area Networks • Wide Area Networks • Wireless Networks • Home Networks

  6. Network Types • Classification of interconnected processors by scale.

  7. Local Area Networks • Two LANs • (a) Bus-broadcast • (b) Ring

  8. Metropoliten Area Networks Switch • Two MANs • (a) Star-switched • (b) Ring

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

  10. Wide Area Networks Circuit switch • Relation between hosts on LANs and the subnet.

  11. Wide Area Networks • A stream of packets from sender to receiver.

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

  13. Wireless Networks • (a) Bluetooth configuration • (b) Wireless LAN

  14. 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).

  15. Network Hardware • Transmission medium • Transceivers: transmitters and receivers on the point-to-point connections • Multiplexers, demultiplexers • Packet and circuit switches • Bridges • Routers • Servers, gateways, management units

  16. Transmission Medium • Air: different frequency bands • Wires: twisted pairs • Coaxial cables • Optical fibers

  17. Transceivers • Transmitters perform modulation and coding to provide efficient and reliable communication. • Receivers perform the reverse operations. • Depending on the medium transceivers are electronic devices, antenas, or lasers and photodiodes.

  18. Multiplexers and Demultiplexers • Multiplexers receive multiple lower bit-rate streams of data and according to some rule transmit the higher bit-rate stream of data. • Demultiplexers do the opposite.

  19. Circuit and Packet Switches • It does not make sense to connect every user with every other user in the network. • Circuit and packet switches connect multiple inputs to multiple outputs. • In circuit switches, the configuration pattern changes on a slow time scale. • In packet switches, the configuration changes on a packet-per-packet basis.

  20. Servers, Gateways, etc. • Servers store various kinds of information for users, for example DNS databases, e-mails, web pages and provide it to the users. • Gateways convert data format, and negotiate QoS with the network.

  21. Layered Structure of Networks • Layers, protocols, and interfaces.

  22. Protocol Hierarchies • Example information flow supporting virtual communication in layer 5.

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

  24. Services to Protocols Relationship • The relationship between a service and a protocol.

  25. Reference Models with Layers • A layer should have well defined function • Function of a layer should be internatinationally standardized • The information flow between interfaces should be minimized

  26. Reference Models • The OSI reference model • The TCP/IP reference model • Hybrid reference model

  27. Reference Models The OSI reference model.

  28. Reference Models • The TCP/IP reference model.

  29. Reference Models • Protocols and networks in the TCP/IP model initially.

  30. Comparing OSI and TCP/IP Models • Concepts central to the OSI model • Services • Interfaces • Protocols • Concept of TCP/IP • Implementation of the required functionality with three layers

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

  32. Bad Timing • The apocalypse of the two elephants.

  33. A Critique of the TCP/IP Reference Model • Problems: • Service, interface, and protocol not distinguished • Not a general model • Host-to-network “layer” not really a layer • No mention of physical and data link layers • Minor protocols deeply entrenched, hard to replace

  34. Hybrid Model • The hybrid reference model to be used in this book.

  35. Example Networks • The Internet • Ethernet • Wireless LANs: 802.11

  36. Example Networks • 1960. Barn from RAND co. first proposal • 1957 Advanced Research Project Agency (ARPA) • 1967 Larry Roberts proposes ARPANET, that was implemented by BBN co. • Interface Message Processors (IMP) were connected by 54kbps links. Protocols: host-IMP, IMP-IMP, host-host • 1969 experimental network, UCLA, UCSB, Stanford University, Yuta University

  37. The ARPANET • (a) Structure of the telephone system. • (b) Baran’s proposed distributed switching system.

  38. The ARPANET • The original ARPANET design.

  39. The ARPANET • Growth of the ARPANET (a) December 1969. (b) July 1970. • (c) March 1971. (d) April 1972. (e) September 1972.

  40. TCP/IP Development • In 1974, TCP/IP model has been established by Cerf and Kahn, and incorporated into Berkeley UNIX. • Because of the large number of hosts, domain name system (DNS) was created in 1980s.

  41. NSFNET • NSF (National Science Foundation) invested into the network for all universities. • Backbone included supercomputers at several universities, it is connected to ARPANET at Carnegie-Mellon university. • MCI rented cables at 448kbps, and IBM provided computers as routers.

  42. NSFNET • The NSFNET backbone in 1988.

  43. Further Development • 1990 non-profit organization Advanced Networks and Services (ANS) started comercialization, and improved speed to 45Mbps, ANSNET started. In 1995 sold to AOL • In nineties EuropaNET and EBONE are developed

  44. Internet Usage • Traditional applications (1970 – 1990) • E-mail • News • Remote login • File transfer • World Wide Web developed by CERN physicist Tim Bernars-Lee, and Mark Andressen at National Center for Supercomputer applications

  45. Architecture of the Internet • Overview of the Internet.

  46. Ethernet • Bob Metacalfe graduated MIT and Harvard, and worked on Hawaii on ALOHANET. • He designed first computer LAN at Xerox Parc in Palo Alto. • DEC, Intel, Xerox make DIX standard that becomes IEEE802.3 • Metcalfe founds 3Com

  47. Ethernet • Architecture of the original Ethernet.

  48. Wireless LANs • (a) Wireless networking with a base station. • (b) Ad hoc networking.

  49. Wireless LANs • The range of a single radio may not cover the entire system.

  50. Wireless LANs • A multicell 802.11 network.

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