7. Computer Networks

Chapter 7: Computer Networks

Learning Objectives

  • Define a computer network and its purpose in modern communication.

  • Describe several uses for networks in various sectors including personal, business, and government.

  • Understand key characteristics of a network: topology, architecture, and size, and how these affect network performance and design.

  • Comprehend how data travels over a network, including the route data takes from sender to receiver.

  • Identify wired and wireless networking media, and their respective data transmission methods and limitations.

  • Recognize common communications protocols and networking standards, understanding their roles in ensuring efficient communication.

  • List various types of networking hardware, detailing their functions and interactions within a network.

Overview

  • Definition of a computer network as a framework for communication, data sharing, and resource management.

  • Common networking applications, terminology, and their significance in daily operation.

  • Discussion on technical issues related to networks such as latency, bandwidth, and security concerns, including encryption and access control measures needed to secure networks.

  • Examination of different types of transmission media and communications protocols essential for successful networking.

  • Overview of hardware components used in networks, their functions, and importance in ensuring network stability and performance.

What is a Network?

A computer network is defined as a connected system enabling the sharing of hardware resources, data, and information between various devices. It facilitates seamless communication, efficient data management, and facilitates resource sharing (such as printers, scanners, or cloud storage services). It allows users to access information and services from various locations, enhancing productivity and collaboration.

Networks vary greatly in size, complexity, and purpose, ranging from small home networks to vast global infrastructures like the Internet, which connects billions of devices globally, enabling online services, social interaction, and business transactions. Networking is vital for modern businesses, where tasks such as data analysis, customer engagement, and supply chain management depend heavily on reliable and fast data transfer.

Networking Applications

  • The Internet: The largest and most significant global network, serving billions of users and devices, providing access to a vast array of information, online services, and communication platforms.

  • Telephone Service: One of the earliest forms of networking, allowing voice communication over wired networks, impacting personal and business communication significantly.

  • Mobile Phones: Leverage advanced wireless communication technologies (such as 4G, 5G) to provide voice and data services on the go, including internet browsing, social media access, and instant messaging.

  • Cellular Phones: Operate within close geographical proximity to cell towers, utilizing various frequency bands; they may include dual-mode options allowing users to switch between GSM and CDMA networks to enhance connectivity and service.

  • Television and Radio: Broadcast networks that deliver multimedia content to consumers via terrestrial, satellite, or cable systems, integrating digital technologies for better image and sound quality.

  • GPS (Global Positioning System): Utilizes satellite technology to provide precise geographic location information, crucial for navigation, mapping, and location-based services in various applications, including logistics and emergency services.

  • Monitoring Systems: Capitalizing on networking technology to track and manage objects and individuals, widely used in security (CCTV), logistics (fleet tracking), and environmental monitoring systems.

  • Telemedicine: Provides remote diagnosis and monitoring of patients, enhancing the accessibility of healthcare through the use of specialized software and networks for video calls and patient data management.

Network Characteristics

Wired vs. Wireless Networks:

  • Wired Networks: Devices are connected using physical cables (e.g., Ethernet cables, fiber optics). This setup is often favored in high-performance environments due to its stability, speed, and security. Wired networks generally have lower latency and are less susceptible to interference compared to wireless networks.

  • Wireless Networks: Devices connect without cables, utilizing radio waves or infrared technology. These networks provide flexibility and convenience, allowing users to connect from different locations; however, they can face challenges such as interference from electronic devices, limited range, and increased vulnerability to unauthorized access or eavesdropping if not properly secured.

Network Topologies:

Different configurations include:

  • Star: All devices connect to a central hub (switch or router); easy to manage and troubleshoot, but if the central hub fails, the entire network can go down.

  • Bus: All devices share a common communication line or cable; a simple and cost-effective design that can suffer from performance constraints as more devices are added, making it highly dependent on reliable cabling.

  • Mesh: Every device connects to every other device, offering high redundancy and reliability; if one link fails, data can take an alternative route. This design is complex and costly to implement due to extensive cabling or the need for sophisticated wireless setups.

Network Architectures:

  • Client-Server: A centralized model whereby client devices request services and resources from servers, which manage data and services. This architecture is commonly used in enterprise environments for its scalability and manageability.

  • Peer-to-Peer (P2P): Each device, or peer, has equal privileges and can share resources directly with one another without central management; this model allows for efficient use of resources in smaller networks but can lead to security and management issues as it scales.

Network Size:

Different scales include:

  • Personal Area Networks (PAN): Small networks designed for personal devices, such as connecting a smartphone to a laptop or wearable technology via Bluetooth.

  • Local Area Networks (LAN): Generally confined to a limited geographical area such as a single building or campus, commonly used in businesses and educational institutions for connecting devices and sharing resources within close proximity.

  • Metropolitan Area Networks (MAN): Larger networks covering a city or a large campus, typically used to interconnect multiple LANs within a specific geographical area, often used by government entities or universities.

  • Wide Area Networks (WAN): Extensive geographical networks that connect larger numbers of users across cities, countries, or global locations. WANs are often composed of multiple interconnected LANs and are used by large organizations and telecom companies.

Data Transmission Characteristics

  • Bandwidth: Represents the maximum data transfer rate within a network, expressed in bits per second (bps), which directly influences the speed and volume of data that can be transmitted simultaneously. It’s essential for ensuring smooth data transfer, especially for bandwidth-heavy applications like video conferencing and online gaming.

  • Types of Signals: Data can be transmitted using analog signals (continuous waveforms) or digital signals (discrete values), where digital signals are more prevalent due to their resilience to noise and interference.

  • Transmission Methods: Include Serial (where bits are sent one at a time) and Parallel (where multiple bits are sent simultaneously), each having its applications based on context and required speed.

  • Timing Methods: Include Synchronous (data is sent in sync with a clock signal), Asynchronous (data is sent at irregular intervals, often with start and stop bits), and Isochronous (data is delivered at consistent intervals, crucial for applications requiring time-sensitive data like audio or video).

  • Transmission Directions: Varieties include Simplex (one-way communication), Half-Duplex (two-way communication but not simultaneously), and Full-Duplex (two-way communication occurring simultaneously, beneficial for real-time interactions).

  • Delivery Methods: Circuit-Switching (dedicated communication path established for the duration of transmission) vs. Packet-Switching (data is broken into packets that take independent paths through the network), the latter being more efficient for data transfer.

Networking Media

Wired Media:

  • Twisted-Pair Cables: Comprised of pairs of insulated wires twisted together, commonly used in LANs due to their cost-effectiveness and ease of installation, reducing electromagnetic interference.

  • Coaxial Cables: Used for broadband internet and television cable connections, comprising a central conductor surrounded by insulation, shielding, and an outer cover, providing excellent resistance to interference and signal degradation over long distances.

  • Fiber-Optic Cables: Consist of thin strands of glass or plastic that transmit data as light signals. Fiber-optic technology supports higher bandwidth and longer distances compared to traditional copper cables, making it ideal for backbone installations in large networks.

Wireless Media:

Data transmission is accomplished through radio signals across the electromagnetic spectrum, utilizing various technologies such as:

  • Cellular Networks (e.g., 4G, 5G): Facilitate high-speed internet access over wide areas, supporting mobile devices and IoT applications with low latency and high data rates due to advancements in cellular technology.

  • Microwave Transmission: Suitable for long-distance communications that require line-of-sight setups, often used for point-to-point links between tall towers or satellite communications.

  • Infrared Transmission: Primarily used for short-range and line-of-sight applications, such as remote controls and data transfer between devices within a close proximity.

Communications Protocols and Networking Standards

Protocols:

Sets of rules governing data transmission; key protocols include:

  • TCP/IP: The foundational protocol suite for the Internet and its services, managing how data packets are addressed, transmitted, and routed.

  • HTTP: Protocol for transferring hypertext pages on the World Wide Web, ensuring that web browsers can communicate with web servers and retrieve web content.

  • FTP: Protocol designed for transferring files between devices on a network, allowing users to upload and download files to and from servers.

  • SMTP: Used for sending emails, facilitating communication between email clients and servers to ensure successful message delivery.

Standards:

Criteria established by organizations (such as IEEE and IETF) to ensure consistency and reliability across different networking systems, increasing interoperability and facilitating smoother communication between heterogeneous networks.

Networking Hardware

A variety of hardware components facilitate networking:

  • Network Adapter: A critical component that allows devices (computers, smartphones) to connect to a network, either wired (Ethernet) or wireless (Wi-Fi).

  • Modem: Converts digital data from a computer into a format suitable for transmission over telephone lines or coaxial cables, enabling internet connectivity.

  • Switch: A hardware device that connects multiple devices within a LAN, directing data traffic intelligently to ensure efficient communication without data collisions.

  • Router: Connects multiple networks and directs data traffic between them, managing the pathways that data packets take based on user-defined policies and network conditions.

  • Wireless Access Point (WAP): Enables wireless devices to connect to a wired network using Wi-Fi. WAPs can extend coverage for a wireless network, allowing more devices to access the network.

  • Additional Hardware: Includes repeaters (to amplify signals for long-distance transmission), bridges (to extend networks and connect different network types), gateways (to interface between disparate networks), and concentrators (to connect multiple network devices and simplify data management).