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Data Communications, Kwangwoon 1- 1

Data Communications

Data Communications and Networking

Behrouz A. Forouzan, 4

th

Edition

McGraw-Hill

Data Communications, Kwangwoon 1- 2

Part 1 Overview

Chapter 1 Introduction

Chapter 2 Network Models

Data Communications, Kwangwoon 1- 4

Data Communications

• (^) Data
  • (^) Information presented in whatever form is agreed upon by the parties creating and using the data
• (^) Data communication
  • (^) Exchange of data between two devices
  • (^) Via some form of transmission medium
• (^) Fundamental characteristics of data communication
  • (^) Delivery
  • (^) Accuracy
  • (^) Timeliness
  • (^) Jitter : Variation in the packet arrival time
• (^) Telecommunication: communication at a distance

(‘tele’ in Greek=‘far”)

Data Communications, Kwangwoon 1- 5

Five Components of Data Communication

• (^) Message: Information(data) to be communicated
• (^) Sender
• (^) Receiver
• (^) Transmission medium: Physical path by which a message travels
• (^) Protocol: A set of rules that govern data communication

Data Communications, Kwangwoon 1- 7

Data Flow

• (^) Simplex
  • (^) Unidirectional
  • (^) As on a one-way street
• (^) Half-duplex
  • (^) Both transmit and receive possible, but not at the same time
  • (^) Like a one-lane road with two-directional traffic
  • (^) Walkie-talkie, CB radio
• (^) Full-duplex
  • (^) Transmit and receive simultaneously
  • (^) Like a two-way street, telephone network
  • (^) Channel capacity must be divided between two directions

Data Communications, Kwangwoon 1- 8

Network

• (^) Network: A set of devices (nodes) connected by communication links
• (^) Node: Computer, printer, or any device capable of sending and/or receiving data
• (^) To be considered effective and efficient, a network must meet a number of criteria

Data Communications, Kwangwoon 1- 10

Type of Connection

Data Communications, Kwangwoon 1- 11

Type of Connection

• (^) Point-to-point
  • (^) Dedicated link between two devices
  • (^) The entire capacity of the channel is reserved
  • (^) Ex) Microwave link, TV remote control
• (^) Multipoint
  • (^) More than two devices share a single link
  • (^) Capacity of the channel is either
    • (^) Spatially shared : Devices can use the link simultaneously
    • (^) Timeshare : Users take turns

Data Communications, Kwangwoon 1- 13

Star Topology

• (^) Dedicated point-to-point link only to a central controller, called a hub
• (^) Hub acts as an exchange: No direct traffic between devices
• (^) Advantages: Less expensive, robust
• (^) Disadvantages: dependency of the whole on one single point, the hub

Data Communications, Kwangwoon 1- 14

Bus Topology

• (^) One long cable that links all nodes
• (^) tap, drop line, cable end
• (^) limit on the # of devices, distance between nodes
• (^) Advantages: Easy installation, cheap
• (^) Disadvantages: Difficult reconfiguration, no fault isolation, a fault or break in the bus stops all transmission

Data Communications, Kwangwoon 1- 16

Hybrid Topology

• (^) Example: Main star topology with each branch connecting several stations in a bus topology
• (^) To share the advantages from various topologies

Data Communications, Kwangwoon 1- 17

Mesh Topology

• (^) Dedicated point-to-point link to every other nodes
• (^) A mesh network with n nodes has n(n-1)/2 links. A node has n-1 I/O ports (links)
• (^) Advantages: No traffic problems, robust, security, easy fault identification & isolation
• (^) Disadvantages: Difficult installation/reconfiguration, space, cost

Data Communications, Kwangwoon 1- 19

LAN

• (^) Usually privately owned
• (^) A network for a single office, building, or campus  a few Km
• (^) Common LAN topologies: bus, ring, star
• (^) An isolated LAN connecting 12 computers to a hub in a closet

Data Communications, Kwangwoon 1- 20

MAN

• (^) Designed to extend to an entire city
• (^) Cable TV network, a company’s connected LANs
• (^) Owned by a private or a public company