CHAPTER 2: COMMUNICATION AND NETWORKING

2.1 NETWORKS INCLUDING THE INTERNET2.1.1 Introduction to Networks

Definition: Networking devices are interconnected devices that enable fast data transmission within a network.

Benefits of Networking:

1. File Sharing: Easily share data between different interconnected devices
2. Resource Sharing: Use network-connected output devices like printers or share software
3. Higher Storage: Files can be stored in network-connected storage mediums
4. Communication: Email and messaging between users
5. Centralized Management: Easier to backup and secure data

2.1.2 Types of Networks

LAN (Local Area Network):

WAN (Wide Area Network):

2.1.3 Network Models

Client-Server Model:

• A dedicated server provides applications (administration of users, security, and resources)
• Clients access resources from the server
• Server manages all central functions

Server Types:

• Print Server: Manages print jobs from client computers
• File Sharing Server: Clients access software and user data files stored on the server
• Proxy Server: Acts as intermediary for internet requests
• Email Server: For sending, receiving, and storing emails
• Database Server: Manages DBMS
• Domain Controller Server: Manages user accounts (IDs & passwords)

Client-Server Login Process:

1. Client sends login request to server
2. Server processes request
3. Server grants access if user ID & password are recognized

Thin Clients vs Thick Clients:

Peer-to-Peer (P2P) Network:

• Decentralized network
• Each computer operates independently as a 'peer'
• Acts as both client and server
• No central server required
• Common in file sharing applications (BitTorrent)

Comparison:

2.1.4 Network Topologies

Bus Topology:

• Single line (bus) connects all devices
• Terminators at each end
• All computers can read data being sent between any two computers
• Disadvantage: Unsuitable for heavy traffic due to frequent collisions
• Uses CSMA/CD for collision detection

Star Topology:

• Central server/switch with all computers connected via dedicated connections
• Server can send packets to different devices simultaneously
• No collisions possible
• Most common in modern networks

Mesh Topology:

• Every device (node) is directly interconnected with all other devices
• Commonly used for wireless networks
• High redundancy (if one path fails, another can be used)

Hybrid Topology:

• Combination of two or more topologies
• Example: Connection between two or more LANs of different topologies

2.1.5 Transmission Media

Wired Networks:

Copper Cable:

Fibre-Optic Cable:

Wireless Networks:

2.1.6 Ethernet

Definition: The most common wired medium for data transmission in LANs or WANs.

CSMA/CD (Carrier Sense Multiple Access with Collision Detection):

Process:

1. Device checks if channel is busy before transmitting
2. If busy, device waits a random time before retrying
3. During transmission, device listens for other transmissions
4. If collision occurs, transmission is aborted
5. Both devices wait random times before retrying

2.1.7 Bit Streaming

Definition: Sequence of digital signals (bits) transferred over a communication path at high speeds.

Types:

Real-time Streaming:

• Live events captured and transmitted directly
• Cannot be paused, fast-forwarded, etc.
• Example: Live TV, video conferencing

On-demand Streaming:

• Pre-existing files are converted and streamed as requested
• Can be paused, fast-forwarded, etc.
• Example: YouTube, Netflix

Importance of High Broadband Speed:

• User has to download and display bits simultaneously
• Higher quality media requires faster speeds
• Real-time streaming needs higher speeds for simultaneous data requests

2.1.8 Cloud Computing

Definition: On-demand provision of computing services over the internet.

Services:

• Infrastructure: Storage capacity and higher processing power
• Platform: Software, testing & debugging resources

Public Cloud vs Private Cloud:

Benefits:

• Less technical knowledge required
• Easy to implement
• Flexibility to scale with growth

Drawbacks:

• Cannot access resources if bandwidth issues
• Poor data privacy (potential data leakage in multi-tenant architecture)

2.1.9 Internet and World Wide Web

Internet:

• Massive, open network of networks
• Uses TCP/IP protocol
• IP addresses identify devices

World Wide Web (WWW):

• Collection of web pages stored on websites
• Uses protocols (HTTP/HTTPS) to transmit data

2.1.10 Network Hardware

2.1.11 IP Addressing

IPv4:

• 32-bit address
• 4 blocks separated by dots (e.g., 192.168.1.1)
• Each block: 0-255

IPv6:

• 128-bit address
• 8 blocks separated by colons
• Each block: 4 hex values (0000-FFFF)
• Can be shortened by removing consecutive zero blocks

IP Address Structure:

• Network Identifier (NetID): Identifies the network
• Host Identifier (HostID): Identifies the device within the network

Subnetting:

• Practice of dividing a network into two or more sub-networks
• IP address broken into: NetID + SubnetID + HostID

Public vs Private IP:

• Public IP: Provided by ISP; unique; accessible from internet
• Private IP: Issued by LAN's router; only accessible within LAN
• NAT (Network Address Translation) required for private IPs to access internet

Static vs Dynamic:

• Static: Never changes; used for servers, VPNs
• Dynamic: Changes regularly; more secure; used for general users

2.1.12 DNS (Domain Name Service)

Definition: A naming system that maps domain names to IP addresses.

Function:

• Hierarchy of DNS servers
• Database of URLs and corresponding IP addresses
• Translates human-readable domain names to IP addresses