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CS 455/555: Spring 2003

CS 455/555: Spring 2003. Chapter 1: Introduction. Uses of Computer Networks. Networks for Companies Networks for People Social issues. Network Hardware. Broadcast Networks versus Point-to-point Networks

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CS 455/555: Spring 2003

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  1. CS 455/555: Spring 2003 Chapter 1: Introduction

  2. Uses of Computer Networks • Networks for Companies • Networks for People • Social issues

  3. Network Hardware • Broadcast Networks versus Point-to-point Networks • Broadcast Networks: Local area networks (LAN), Metropolitan area networks (MAN), Wide-area networks (WAN), Wireless Networks, Internetworks (vs. intranetworks?) • See Figures

  4. Network Software • Protocol Hierarchies See Fig 1-9 through 1-11 • Design Issues for the Layers: Addressing; Rules of data transfer---Simplex, half-duplex, full-duplex; Error control; Ordering of messages; Flow-control---fast sender, slow receiver; message length; multiplexing and demultiplexing; routing • Interfaces and Services: SAP, IDU, SDU, PDU • See Figure 1-12

  5. Network Software (Contd.) • Connection-oriented and Connectionless Service • See Figure 1-13 • Service Primitives • See Figure 1-14 • Services vs. protocols: Services are offered by a layer to the layer above it; A protocol is a set of rules for communication between entities with the same layer

  6. Reference Models • The OSI Reference Model (See Fig. 1-16) • Seven layers: Physical, Datalink, Network, Transport, Presentation, and Application • Data transmission in the OSI protocol (See Fig. 1-17) • The TCP/IP Reference Model (See Fig. 1-18) • Four layers: Host-to-network, Network, Transport, Application (See Fig 1-19)

  7. Comparison of OSI and TCP Reference Models • Read pages 38-44 • It will be more obvious after we study the protocols

  8. ATM (Asynchronous Transfer Mode) • Asynchronous? The sender and receiver are not tied through a common clock • ATM cell: 53 bytes long: 5-byte header and 48-byte data data is sent in terms of cells • Connection-oriented networks: Cell delivery is not guaranteed but their order is (E.g., If 1-10 cells are sent in sequence, then only cells 1-5 and 7-9 may be received; but they are received in that order.) • ATM networks are organized like WANs with speeds of 155 Mbps (actually 155.52), 622 Mbps (4*155.5 = 622), and more.

  9. ATM (Contd.) • ATM Reference model (See Fig. 1-30) • User plane: Deals with data transport, flow control, error correction, and other user functions. • Control plane: Deals with connection management • (See Fig.1-31)

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