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: File Sharing:  Easily share data between different interconnected devices Resource Sharing:  Use network-connected output devices like printers or share software Higher Storage:  Files can be stored in network-connected storage mediums Communication:  Email and messaging between users Centralized Management:  Easier to backup and secure data 2.1.2 Types of Networks LAN (Local Area Network): Characteristic Description Geographic Area Small area, often within the same building Ownership Private ownership Transmission Medium Twisted pair cables, coaxial cables, or Wi-Fi Data Transfer Rate Higher (100 Mbps to 10 Gbps) Congestion Less congestion Setup Cost Lower initial cost WAN (Wide Area Network): Characteristic Description Geographic Area Large area - city, country, or globally Ownership Private or public ownership Transmission Medium PSTN, satellite links, leased lines Data Transfer Rate Lower Congestion Higher congestion Setup Cost Higher initial cost 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: Client sends login request to server Server processes request Server grants access if user ID & password are recognized Thin Clients vs Thick Clients: Thin Clients Thick Clients Runs solely on server resources Processes most application locally No local storage Has local storage and processing power Smaller purchase cost More expensive Requires constant server connection Can work offline Improved security More vulnerable to unauthorized software 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: Feature Client-Server Peer-to-Peer Centralized backup Yes No Initial setup cost Higher Lower Network traffic Higher (goes through server) Lower (direct) Security Better (centralized control) Weaker Reliability Server failure affects all Peer failure affects one 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: Advantages Disadvantages Less expensive Doesn't perform well with small charges Easier to install Affected by electromagnetic interference Flexible Signal degradation over distance Easy to make terminations   Fibre-Optic Cable: Advantages Disadvantages Greater bandwidth Needs expensive optical transmitters/receivers Improved security More difficult to install Lightweight   Less signal boosting required   Used in long-distance communications   Immune to electromagnetic interference   Wireless Networks: Type Advantages Disadvantages Radio Waves Can travel over large distances; inexpensive Low frequency = less data; affected by interference Microwaves Larger bandwidth Physical obstacles interfere; expensive towers Satellites Cost-effective for long-distance Expensive setup; susceptible to interference 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: Device checks if channel is busy before transmitting If busy, device waits a random time before retrying During transmission, device listens for other transmissions If collision occurs, transmission is aborted 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: Feature Public Cloud Private Cloud Access Third-party providers, shared among multiple users Single organization, exclusive access Management Managed by service providers Can be managed internally or outsourced 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 Device Function Router Connects two networks; translates IP addresses; acts as gateway and firewall Switch Connects devices in LAN; broadcasts to all devices simultaneously Server Provides specific functions for computers in the network NIC (Network Interface Card) Provides unique MAC address for wired connection WNIC (Wireless NIC) Provides unique address for WiFi connection WAP (Wireless Access Point) Allows devices to connect via WiFi Bridge Connects two LANs using same protocol Repeater Regenerates signal to prevent attenuation Modem Converts digital to analogue signals for telephone lines 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