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ITEC350 Networks I Lecture 1

ITEC350 Networks I Lecture 1. Hwajung Lee. What is Computer Networks?. A collection of autonomous computers interconnected by a single technology Interconnected via: Copper wire Fiber optics Microwaves Infrared Communication satellites, etc. Why Computer Networks?.

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ITEC350 Networks I Lecture 1

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  1. ITEC350 Networks ILecture 1 Hwajung Lee

  2. What is Computer Networks? • A collection of autonomous computers interconnected by a single technology • Interconnected via: • Copper wire • Fiber optics • Microwaves • Infrared • Communication satellites, etc.

  3. Why Computer Networks? • Business Applications • [Goal1] Resource Sharing • To connect isolated computer and information to be able to extract and correlate information about the entire company. • To make all programs, equipment (ex: printers, scanners, and CD burners), and especially data available to anyone on the network without regard to the physical location of the resource an the user.

  4. [Goal 2] Communication Medium • Electronic mail (e-mail) • Shared resources (ex: shared hard driver) • Videoconferencing, a shared virtual blackboard

  5. [Goal 3] Electronic Commerce (e-commerce) • To do business electronically with other companies. (ex: order the parts of a product from a variety of suppliers) • To do business with consumers over the Internet.

  6. Home Applications • [Goal 1] Access to remote information • Newspapers, Digital library • [Goal 2] Person-to-person communication • Email, Instant messaging, Chat room, Worldwide newsgroups • Peer-to-peer communication (ex: Napster) • Internet phone, Internet video phone, Internet radio, Telelearning

  7. Home Applications (cont.) • [Goal 3] Interactive entertainment • Video on demand, Interactive live television show, Multiperson real-time simulation games – possibly with worldwide shared virtual reality. • [Goal 4] Electronic commerce • Home shopping, Electric flea markets, On-line auctions

  8. Mobile Network Users • [Goal] To have a portable office • Cellular phone, PDA, Military use, Wireless sensor networks, Mobile-commerce, Wearable wireless computers Combinations of wireless networks and mobile computing.

  9. Network Types Based on Roles • Terminal Connection

  10. Network Types Based on Roles • Client-server

  11. Network Types Based on Roles • Peer-to-peer • Computers act as both client and server on the network • There is no reliance on a centralized server to provide access to data and other resources • Compared to a centralized client-server model, peer-to-peer is decentralized, meaning any host can communicate with any other host


  13. Comparison of Basic Topologies

  14. Classification of interconnected processors by scale.

  15. Personal Area Network (PAN) • A person’s body or desk area

  16. Local Area Networks (1) • Local Area Network (LAN) • Limited geographical distance: home, office, building, campus, industrial part • Customer premises operation • User firm chooses technology • User firm needs to manage on ongoing basis • Low cost per bit transmitted • Companies can afford high speed • 100 Mbps to the desktop is typical

  17. Local Area Networks (2) Two broadcast networks (a) Bus (b) Ring

  18. Local Area Networks (3) • Ethernet • Most popular LAN Architecture of the original Ethernet.

  19. Metropolitan Area Networks • Metropolitan Area Network (MAN) • Single urban area (city and its suburbs) • Faster than long-distance WANs • Still slower than LANs

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

  21. WAN • Wide Area Network (WAN) • To link sites • Long distances • Requires the use of carriers to provide service • Limited and complex choices but carrier manages • High cost per bit transmitted • Companies cannot afford high speeds • Usually low speed (56 kbps to a few megabits per second)

  22. Wide Area Networks (1) Relation between hosts on LANs and the subnet.

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

  24. Wireless Networks • Categories of wireless networks: • System interconnection • Wireless LANs • Speed: Upto about 50Mbps • Distance: Tens of meters • Wireless WANs (ex: cellular system) • Speed: below 1Mbps • Distance: Kilometers

  25. Wireless Networks (2) (a) Bluetooth configuration (b) Wireless LAN

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

  27. Standard for Wireless LANs IEEE 802.11 network.

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

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

  30. Protocol Hierarchies The philosopher-translator-secretary architecture.

  31. Connection-Oriented and Connectionless Services (1) • The software used to maintain each protocol is often called a protocol stack • Transport layer protocols can be: • Connectionless, or stateless, which sends each packet without regard to whether any other packet was received by the destination computer (implementation: packet switching, UDP)

  32. Connection-Oriented and Connectionless Services (2) • Connection oriented, or stateful, which maintains information about which packets have been correctly received by the destination computer (implm.:circuit-switching, TCP)

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

  34. Why Standard or Reference Model? • Consumer • Easy to select a product which is compatible with other equipments. • Supplier • Minimize risk when it develops new technologies.

  35. Reference Models • The OSI Reference Model • ISO (International Organization for Standardization) • OSI (Open Systems Interconnection) Model • The TCP/IP Reference Model • TCP (Transmission Control Protocol) • IP (Internet Protocol) • A Critique of the OSI Model and Protocols • A Critique of the TCP/IP Reference Model

  36. OSI Reference Model

  37. OSI Reference Model

  38. The TCP/IP reference model

  39. Conceptual Models of Networking(1)

  40. Acronyms • POP (Post Office Protocol) • FTP (File Transfer Protocol) • UDP (User Datagram Protocol) • TCP (Transmission Control Protocol) • SMTP (Simple Mail Transport Protocol) • HTTP (Hypertext Transport Protocol) • DNS (Domain Name Service) • ICMP (Internet Control Message Protocol) • PPP (Point-to-Point Protocol) • SATNET (Satellite Networks) • IRC (Internet Relay Chat)

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

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

  43. 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

  44. Networking Technologies • Ethernet • Most widely used technology • Three variation of Ethernet based on transmission speed, or bandwidth • Token-ring • Uses a token to identify which computer on the network has the right to transmit data • Not as fast as Ethernet, and may be more expensive

  45. Networking Technologies

  46. Network Standardization • Who’s Who in the Telecommunications World • Who’s Who in the International Standards World • Who’s Who in the Internet Standards World

  47. ITU (International Telecommunication Union) • Main sectors • Radiocommunications • Telecommunications Standardization • Development • Classes of Members • National governments • Sector members • Associate members • Regulatory agencies

  48. IEEE 802 Standards The 802 working groups. The important ones are marked with *. The ones marked with  are hibernating. The one marked with † gave up.

  49. Metric Units The principal metric prefixes.

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