Ch_01 - Introduction

Chapter 1: Introduction to Data Communications and Networking

1.1 Overview of Data Communications

  • Definition: Data communications involve the exchange of data between two devices using transmission media.

  • Telecommunication: Encompasses communication at a distance (telephony, telegraphy, television).

1.1 Data Communication System Evaluation

  • Key Characteristics:

    • Delivery: Accurate delivery of data to the correct destination.

    • Accuracy: Data must be error-free and unaltered.

    • Timeliness: Data must be delivered promptly, especially for real-time applications (audio, video).

    • Jitter: Variability in packet arrival time should be minimal. The variation in packet arrival time should be minimal to ensure consistent quality in audio and video transmissions.

1.1.1 Components of Data Communications

  • A data communications system is comprised of five key components:

    • Sender: The device that sends the message.

    • Receiver: The device that receives the message.

    • Message: The data being communicated.

    • Transmission Medium: The physical path through which the data travels.

    • Protocol: Rules governing the communication process between sender and receiver.

1.1.2 Data Representation

  • Different forms of information include:

    • Text: Encoded as bit patterns (e.g., ASCII, Unicode).

    • Numbers: Converted to binary for for mathematical operations..

    • Images: Composed of pixels with bit patterns based on resolution/color depth.

    • Audio: Captures continuous signals.

    • Video: Can be continuous or consist of discrete images.

1.1.3 Data Flow Types

  • Simplex: Unidirectional communication (e.g., keyboard to computer).

  • Half-Duplex: Bidirectional, but not simultaneous (e.g., walkie-talkies).

  • Full-Duplex: Simultaneous bidirectional communication (e.g., telephone).

1.2 Networks and Topologies

  • Definition: A network is an interconnection of devices enabling communication.

  • Types of Devices:

    • Hosts: PCs, laptops, mobile devices.

    • Connecting Devices: Routers, switches, modems.

1.2.1 Network Criteria

  • Networks must meet criteria of performance, reliability, and security.

1.2.2 Physical Structures in Network Topology

  • Types of Connections:

    • Point-to-Point: Dedicated link between two devices.

    • Multipoint: Multiple devices share a single link.

  • Physical Topologies:

    • Mesh: Every device connects to every other device.

    • Star: Devices connect to a central hub.

    • Bus: All devices connect to a single backbone cable.

    • Ring: Devices are connected in a circular fashion.

  • Advantages/Disadvantages: Each topology has unique benefits regarding cost and performance, chosen based on specific network needs.

1.3 Types of Networks

  • Criteria for Differentiation: Based on size, geographical coverage, and ownership.

1.3.1 Local Area Network (LAN)

  • Definition: A network connecting devices in a limited area (e.g., office, building).

  • Characteristics:

    • Limited geographic span.

    • Devices can share resources (e.g., files, printers).

    • High-speed communication (e.g., Ethernet).

    • Centralized management via a server.

  • Common Examples: Home networks, office networks, school networks.

    Each host in a LAN has an identifier, an address, that uniquely defines the host in the LAN. A packet sent by a host to another host carries both the source host’s and the destination host’s addresses.

    Network devices: Switches, routers, hubs, and modems.

Network protocols: Rules governing how devices communicate (e.g., TCP/IP).

A LAN provides a network infrastructure for devices to communicate and share resources within a localized area.

1.3.2 Wide Area Network (WAN)

  • Definition: A network that covers a large geographic area, often connecting multiple LANs.

  • Characteristics:

    • Extends across cities, states, or countries.

    • Involves multiple interconnected networks.

    • Typically managed by service providers.

  • Common Examples: Internet worldwide, corporate, and government networks.

    Large geographic area: Connects devices over vast distances.

    Multiple networks: Interconnects multiple LANs or other networks.

    Telecommunication infrastructure: Often relies on leased lines, VPNs, or satellite connections.

    Centralized management: Typically managed by a network service provider.

    Routers: Devices that connect networks and route traffic between them.

    Modems: Devices that connect to the internet or other WANs.

    Leased lines: Dedicated, high-speed connections between locations.

VPN (Virtual Private Network): Creates a secure tunnel for data transmission over a public network.

A WAN provides a network infrastructure for devices to communicate and share information over long distances

1.3.3 Switching

  • Definition: A method of connecting networks where a switch forwards data between links.

  • Types of Switched Networks:

    • Circuit-Switched: Establishes a dedicated channel.

    • Packet-Switched: Transmits data in packets over a shared network.

1.3.4 The Internet

  • Definition: A vast interconnected network allowing communication between multiple networks.

1.4 History of the Internet

  • Early History: Networks prior to 1960 included telegraph and phone systems, designed for constant-rate communication.

  • Birth of the Internet: Developed in 1972 by Vint Cerf and Bob Kahn, with the goal of linking dissimilar networks.

  • Current Internet: Rapid growth in infrastructure and applications has popularized the Internet, making it a vital global communication platform.