Computer Security Fundamentals - Chapter 2: Networks and the Internet

Chapter 2: Networks and the Internet

Objectives of Chapter 2

  • Identify Major Protocols: Recognize each major protocol used in network communication, such as FTP (File Transfer Protocol) and Telnet, and articulate their specific uses.

  • Connection Methods and Speeds: Understand the various connection methods for networks as well as their respective speeds.

  • Network Devices Comparison: Compare and contrast various network devices, identifying their functions and capabilities.

  • Network Protocols: Identify and explain the various network protocols in use today.

  • Data Transmission: Comprehend how data is transmitted across a network.

  • Internet Functionality: Explain how the Internet operates, including the role of IP addresses and URLs (Uniform Resource Locators).

  • History of the Internet: Provide a brief historical overview of the Internet.

  • Network Utilities: Demonstrate the usage of network utilities such as ping, IPConfig, and tracert.

  • OSI Model: Describe the OSI (Open Systems Interconnection) model of network communication and explain the significance of MAC (Media Access Control) addresses.

Network Basics

  • Definition of Network: A network consists of two or more computers connected using a Network Interface Card (NIC).

  • Wireless Transmission: Networks utilize radio signals to communicate with a nearby wireless router or hub.

  • Antenna Requirement: A wireless router, hub, or NIC must be equipped with an antenna to transmit and receive signals.

Physical Connection: Local Networks

  • Wired NICs: Traditional wired NICs utilize an RJ-45 connection.

  • Cabling Standards: Most networks employ Cat 5 or Cat 6 cables for connections.

Types of Connection Devices

  • Hub:

    • Simplest networking device.

    • Creates a basic network structure.

    • Sends traffic through all ports without any routing or switching.

  • Repeater:

    • A device that amplifies or strengthens the signal.

    • Essential when cable lengths exceed their maximum limits.

  • Switch:

    • An intelligent hub that sends packets exclusively to the designated host.

  • Router:

    • A more sophisticated device that directs network traffic specifically to the intended network, enhancing efficiency.

Internet Connection Types and Speeds

  • Wireless Standards:

    • IEEE 802.11: Specifies guidelines for wireless networking, with different letter designations indicating varying wireless speeds (e.g., 802.11n).

  • Bluetooth:

    • Short-distance radio technology operating within the frequency range of 2.4GHz to 2.485GHz, allowing devices within range to recognize each other.

Data Transmission in Networks

  • Packet-Based Communication: Networks convey binary information in the form of packets following certain protocols and ports.

  • Definitions:

    • Protocols: Rules governing communication over networks and the Internet.

    • Transmission Control Protocol (TCP): Connection-oriented protocol that establishes a connection before transmitting data.

    • Internet Protocol (IP): A connectionless protocol that transmits data without establishing a prior connection.

    • Ports: Numeric labels denoting specific endpoints for communication pathways (e.g., a combination of an IP address and a port number is called a socket).

How the Internet Works

  • Connecting to the Internet:

    • Users access the Internet through an Internet Service Provider (ISP).

    • The ISP links to other ISPs or a backbone provider.

    • Backbone providers connect through a network access point (NAP), facilitating broader access.

IP Addresses

  • Importance:

    • IP addresses are essential identifiers for navigating the Internet, akin to a Social Security number.

  • Composition:

    • Usually represented in binary, consisting of four octets separated by decimals.

    • The first octet indicates the IP class.

Availability of IP Addresses

  • IPv4 vs. IPv6:

    • IP addresses can be in IPv4 or IPv6 format due to the limited availability of IPs.

  • Subnetting:

    • Subnet: A segment of a network sharing a common subnet address.

    • Subnet Masks: Define the subnet associated with an IP address.

    • Classless Inter-Domain Routing (CIDR): Describes subnets more flexibly alongside IP addresses.

Uniform Resource Locators (URLs)

  • Functionality:

    • URLs serve as user-friendly identifiers for websites, which the Domain Name System (DNS) translates into IP addresses.

  • Error Messages:

    • Different classes of error messages reflect various issues:

    • 100 Series: Informational messages.

    • 200 Series: Indicate success (often not explicitly reported).

    • 300 Series: Redirection messages.

    • 400 Series: Client-side errors.

    • 500 Series: Server-side errors.

History of the Internet

  • Origins:

    • Roots trace back to the Cold War, with significant milestones:

    • 1957: Formation of ARPA (Advanced Research Projects Agency).

    • 1968: Commissioning of ARPANET, an early form of the Internet with four key nodes.

    • 1979: Emergence of Usenet newsgroups.

    • 1990: Development of HTTP by Tim Berners-Lee.

    • 1993: Introduction of the first graphical web browser, Mosaic.

Basic Network Utilities

  • Command Line Utilities: Executable from a command prompt or shell (Windows, UNIX/Linux):

    • IPConfig: Displays system information related to IP addresses, subnet masks, and gateways.

    • Ping: Tests network connectivity and measures response times for packets.

    • Tracert: Identifies each 'hop' in the data transmission path between source and destination.

    • Netstat: Provides current network status and active connections.

    • NSLookup: Verifies the functioning of DNS servers and executes DNS queries.

    • ARP: Maps IP addresses to MAC addresses.

    • Route: Displays IP routing table.

    • PathPing: Combines features of ping and tracert, providing data on latency across hops.

Other Network Devices

  • Firewalls:

    • A combination of hardware and software that filters and restricts incoming and outgoing network traffic based on set security rules.

  • Proxy Servers:

    • Serve to disguise the original network's IP address from the external sites it accesses, providing an extra layer of privacy.

The OSI Model

  • Definition:

    • The OSI model is a seven-layer model providing a comprehensive framework for understanding network communications.

    • Functions as both a diagnostic and troubleshooting tool.

    • Layer structure (from top to bottom):

    • Application

    • Presentation

    • Session

    • Transport

    • Network

    • Data Link

    • Physical

The TCP/IP Model

  • Overview:

    • The TCP/IP model condenses the functionality of the OSI model into four layers.

    • Acts similarly in describing network communications and serves as a diagnostic tool.

    • Layer names are:

    • Application

    • Transport

    • Internet

    • Network Access

MAC Addresses

  • Description:

    • MAC addresses signify unique identifiers for NICs and are specified within the data link layer of the OSI model.

    • Represented as a 6-byte hexadecimal number.

    • The ARP protocol is utilized for mapping IP addresses to MAC addresses.

Cloud Computing

  • Definition:

    • Encompasses network access to shared computational resources and services.

  • Primary Classifications:

    • Public Clouds: Available to the general public or industry groups.

    • Private Clouds: Exclusively used by a single organization.

    • Community Clouds: Designed to serve specific community-related needs across multiple organizations.

Summary of Chapter 2

  • The chapter covers fundamental aspects of networks and the Internet including networks’ structure, key hardware components, usage of network utilities, and the essentials of the OSI model to enable a foundational understanding of network operations.