This guide covers the key concepts for IB CS SL Topic 3, focusing on understanding different network types, transmission, protocols, and security. Estimated study time: 20-25 minutes.
3.1.1: Types of Networks
Networks connect computers (nodes) to share resources and communicate.
LAN (Local Area Network): Connects nodes in a small geographic area (e.g., building, school). Typically uses private connections (Ethernet cables, local WiFi). Fast speeds.
WAN (Wide Area Network): Connects nodes over a large geographic area (e.g., cities, countries). Often uses leased public communication lines (e.g., fiber optic cables provided by ISPs). The Internet is the largest WAN.
WLAN (Wireless Local Area Network): A LAN using wireless technology (WiFi) instead of cables.
(W)PAN (Personal Area Network): Connects devices for one individual over a very short range (e.g., Bluetooth connecting headphones to a phone). Can be wired (USB) or wireless (Bluetooth).
SAN (Storage Area Network): A dedicated network connecting servers to storage devices. Appears as a local drive to the OS but uses network infrastructure. High speed, used in large organizations.
VPN (Virtual Private Network): Creates a secure, encrypted connection (tunnel) over a public network (like the Internet) to access a private network.
VLAN (Virtual Local Area Network): Logically segments a physical LAN into multiple broadcast domains. Improves security and traffic management without physical rewiring. (Logical concept, not physical).
Internet: A global network of interconnected networks (WANs, LANs etc.).
Intranet: A private network within an organization, using internet technologies (web pages, browsers) but accessible only internally.
Extranet: An Intranet that is partially accessible to authorized outsiders (e.g., suppliers, customers).
P2P (Peer-to-Peer): A distributed network where nodes ("peers") share resources directly with each other without a central server. Each peer can act as both client and server. (e.g., BitTorrent).
Basic Topologies (Physical Layout)
Star: All nodes connect to a central device (hub/switch). Easy to manage, failure of one node doesn't affect others, but central device failure takes down the network.
Bus: All nodes connect to a single main cable (backbone). Simple, cheap, but cable failure affects all nodes, and collisions can occur.
Ring: Nodes connect in a circular loop. Data travels in one direction. Less common now.
3.1.2: Importance of Standards
Standards are agreed-upon rules and specifications for hardware and software.
Interoperability: Ensure devices from different manufacturers can communicate. (e.g., WiFi standard allows any WiFi laptop to connect to any WiFi router).
Consistency: Provide a common ground for development, reducing complexity.
Competition & Choice: Allow consumers to mix and match products without being locked into one vendor.
Without standards: Communication would be difficult or impossible, creating isolated systems.
3.1.3: Layered Communication Model
Communication over networks is broken down into layers (like the OSI or TCP/IP model). Each layer performs specific tasks and passes data to the next layer.
Concept: Divides complex networking tasks into smaller, manageable parts.
Benefits: Standardization, modularity (changes in one layer don't break others), easier troubleshooting.
Example Layers (Simplified TCP/IP):
Application: User interacts here (HTTP, FTP, SMTP). Creates data.
Transport: Manages end-to-end connections, reliability (TCP), speed (UDP). Breaks data into segments.
Network/Internet: Handles addressing (IP addresses) and routing packets across networks.
Data Link/Network Access: Manages physical addressing (MAC addresses) and error checking on the local link. Puts data into frames.
Physical: Transmits raw bits (0s and 1s) over the physical medium (cables, radio waves).
Data is encapsulated (headers added) as it goes down the layers on the sending side, and decapsulated (headers removed) as it goes up on the receiving side.
3.1.4 & 3.1.5: Virtual Private Networks (VPN)
VPN (Virtual Private Network): A technology that creates a secure and encrypted connection (a "tunnel") over a less secure network, such as the internet, allowing users to access a private network remotely as if they were directly connected.
Technologies Required:
Internet Access (for both client and server).
VPN Server (Hardware or Software) at the private network's edge.
VPN Client Software on the remote user's device.
Encryption Protocols (e.g., OpenVPN, IPSec) to secure the tunnel.
Authentication methods to verify users.
Evaluation of VPN Use:
Advantages
Security: Encrypts data, protecting it from eavesdropping on public networks (like public WiFi).
Remote Access: Allows users to securely access internal resources (files, servers) from anywhere. Enables telecommuting/remote work.
Bypass Geo-restrictions: Can make traffic appear to originate from the VPN server's location.
Anonymity: Hides the user's real IP address from websites/services.
Disadvantages
Speed Reduction: Encryption/decryption adds overhead, potentially slowing down the connection.
Complexity: Can require some technical setup (though many services simplify this).
Cost: Commercial VPN services often have subscription fees. Setting up a private one requires resources.
Trust: Users must trust the VPN provider not to log or misuse their traffic (for commercial VPNs).
Blocking: Some services or countries may block VPN traffic.
3.1.6 & 3.1.7: Protocols & Data Packets
Protocol: A set of rules that govern how data is formatted, transmitted, and received between devices in a network. Essential for communication. (Examples: HTTP, TCP, IP, Ethernet, WiFi).
Data Packet: A small unit of data transmitted over a network. Contains a portion of the original data plus control information (header/trailer) like source/destination addresses, sequence numbers, error detection codes.
Why Protocols are Necessary:
Formatting: Define message structure.
Addressing: Ensure data reaches the correct destination.
Flow Control: Prevent fast senders from overwhelming slow receivers.
Error Control: Detect (and sometimes correct) errors during transmission.
Session Management: Establish, maintain, and terminate connections.
Congestion Control: Manage network traffic to avoid gridlock.
Without protocols: Devices wouldn't understand each other's signals; communication would fail.
3.1.8: Variable Data Transmission Speed
Network speed (bandwidth/throughput) can vary significantly due to:
Network Traffic/Congestion: More users/data = slower speeds (like rush hour on a highway).
Time of Day: Peak usage times often lead to slower speeds.
Type of Connection/Media: Fiber optic > Ethernet Cable (Cat 6) > Coaxial Cable > DSL > WiFi > Mobile Data (3G/4G/5G) - generally.
ISP Service Plan: Users pay for specific maximum speeds.
Distance: Signal strength degrades over distance (especially for DSL and wireless).
Server Load: The speed of the server you are connecting to matters.
Throttling: ISPs might intentionally slow down certain traffic or users.
Cable Quality/Interference: Poor wiring or radio interference (for wireless) can reduce speed.
3.1.9: Data Compression
Compression: Encoding data using fewer bits than the original representation.
Why Compression is Necessary:
Faster Transmission: Smaller files take less time to send over a network. Crucial for large files (video, images).
Reduced Storage Space: Saves disk space for backups and general storage.
Lower Costs: Reduces bandwidth usage, potentially lowering data costs (especially on mobile networks).
Types of Compression:
Lossless: Reduces file size without losing any original data. The original can be perfectly reconstructed. (Used for text, code, some images like PNG, ZIP archives).
Lossy: Achieves much smaller file sizes by permanently removing some "less important" data. Cannot perfectly reconstruct the original. (Used for images (JPEG), audio (MP3), video (MP4)). Good for media where perfect fidelity isn't always necessary.
3.1.10: Transmission Media Characteristics
How data physically travels. Key characteristics: Speed, Cost, Reliability/Distance, Security.
Medium
Description
Speed
Cost
Reliability/Distance
Security
UTP Cable (Ethernet)
Twisted pairs of copper wires. Common in LANs.
Good (100Mbps - 10Gbps)
Low
Moderate (~100m), Susceptible to EMI
Moderate (Physical access needed)
Coaxial Cable
Central copper core, insulation, braided shield. Cable TV/Internet.
Okay (10Mbps - 1Gbps)
Moderate
Better than UTP (~500m), Less EMI susceptible
Moderate
Fiber Optic Cable
Transmits data as pulses of light through glass/plastic strands.
Very High (Gbps - Tbps)
High (Cable & installation)
Very High (Long distances, km), Immune to EMI
High (Difficult to tap without detection)
Wireless (Radio Waves - WiFi/Bluetooth/Cellular)
Transmits data through the air using radio frequencies.
Varies (Mbps - Gbps, depends on standard & conditions)
Low (No cabling), Moderate (Access Points)
Lower (Shorter range, affected by obstacles, interference)
Lower (Signals broadcast, relies heavily on encryption - WPA2/3)
3.1.11: Packet Switching
The dominant method for data transmission on the internet.
Data is broken into packets.
Each packet is addressed independently (source/destination IP).
Packets travel independently across the network, potentially taking different routes. Routers decide the best path for each packet.
Packets are reassembled at the destination.
Advantages: Efficient use of network bandwidth (lines shared), robust (can route around failures), allows multiple communications simultaneously.
Disadvantage: Packets can arrive out of order or be lost (TCP handles reordering/retransmission). Variable delay (jitter).
3.1.12 & 3.1.13: Wireless Networking
Hardware & Software Components:
Hardware:
Nodes (Laptops, phones, printers with wireless capability).
Wireless Network Interface Card (WNIC) in each node.
Wireless Access Point (AP) or Wireless Router: Connects wireless devices to each other and often to a wired network/internet. Broadcasts radio waves (WiFi).
Software:
Network Operating System (NOS) drivers for the WNIC.
Protocol Stack (TCP/IP) for communication.
Utility software for managing connections.
Applications (Browser, email client, etc.).
Evaluation of Wireless Networks:
Advantages
Mobility & Flexibility: Users can connect from anywhere within range.
Ease of Installation: No need to run physical cables. Quicker setup.
Scalability: Relatively easy to add new devices.
Cost (Cabling): Saves on the cost and effort of installing physical wires.
Standards: Global standards (e.g., WiFi 802.11 series) ensure compatibility.
Disadvantages
Security Risks: Signals are broadcast, making them easier to intercept. Relies heavily on strong encryption (WPA2/WPA3).
Interference: Signals affected by other devices (microwaves, cordless phones), walls, and distance.
Speed/Bandwidth: Often slower and less consistent than wired connections (though modern WiFi is fast). Bandwidth is shared among users on an AP.
Limited Range: Signal strength decreases with distance and obstacles.
Health Concerns (Debated): Some concerns raised about long-term exposure to radio frequencies (generally considered safe by most health organizations).
3.1.14: Characteristics of Wireless Network Types
WiFi (Wireless Fidelity / WLAN - 802.11 standards): Most common for home/office LANs. Range typically tens of meters. Speeds vary greatly by standard (a/b/g/n/ac/ax). Operates in unlicensed spectrum (2.4GHz, 5GHz).
WiMAX (Worldwide Interoperability for Microwave Access - 802.16): Longer range than WiFi (kilometers). Designed for Metropolitan Area Networks (MANs), providing broadband access over larger areas. Less common now, often superseded by LTE/5G.
Cellular (3G, 4G/LTE, 5G): Used by mobile phones. Wide area coverage via cell towers. Speeds increase significantly with each generation (3G: ~Mbps, 4G: tens/hundreds Mbps, 5G: Gbps potential). Licensed spectrum. Allows data + voice.
3.1.15 & 3.1.16: Network Security Methods
Protecting networks and data from unauthorized access, use, disclosure, alteration, or destruction. Key concepts: Confidentiality (preventing unauthorized disclosure), Integrity (maintaining accuracy/completeness), Availability (ensuring access when needed).
Methods & Evaluation:
Authentication: Verifying identity.
UserID/Password (Single-Factor): Something you know.
Pros: Simple, widely used.
Cons: Passwords can be guessed, stolen, weak. Doesn't protect against interception.
Two-Factor Authentication (2FA): Combines two different factors (e.g., password + code from phone app/SMS). Something you know + something you have.
Pros: Much stronger than passwords alone.
Cons: Can be slightly less convenient. SMS can be intercepted.
Biometrics (Multi-Factor): Something you are (fingerprint, face scan). Often used with other factors.
Pros: Convenient, hard to replicate.
Cons: Privacy concerns, potential for false positives/negatives.
UserID Management: Assigning unique IDs, managing access rights (permissions) based on roles/groups.
Pros: Controls what authenticated users can do. Centralized management.
Cons: Requires careful administration. IDs can still be stolen/misused if authentication is weak.
Firewalls: Hardware or software that filters traffic entering/leaving a network based on predefined rules (IP addresses, ports, protocols).
Pros: Essential first line of defense, blocks unwanted access.
Cons: Can be complex to configure, doesn't protect against threats from inside or encrypted threats it can't inspect.
Encryption: Scrambling data so it's unreadable without the correct key.
Wireless Encryption (WEP, WPA, WPA2, WPA3): Secures WiFi networks. WEP is broken/insecure. WPA2/WPA3 are recommended.
Pros: Essential for confidentiality on wireless networks. WPA2/3 are strong.
Cons: WEP is insecure. Requires correct configuration (strong password). Adds slight overhead.
General Data Encryption (e.g., SSL/TLS for websites, VPNs): Protects data in transit.
Pros: Provides confidentiality and integrity for transmitted data. Strong algorithms are hard to break.
Cons: Requires processing power (overhead). Needs proper key management. Some encryption can have backdoors. Users often lazy with passwords needed for decryption.
MAC Address Filtering: Allowing only devices with specific, pre-approved MAC addresses (unique hardware identifiers) to connect.
Pros: Adds a small layer of security.
Cons: MAC addresses can be easily spoofed (faked). Managing lists can be cumbersome. Provides minimal real security on its own.
Physical Security: Locking server rooms, securing network equipment, controlling physical access.
Pros: Prevents unauthorized physical access/tampering.
Cons: Can be bypassed if procedures aren't followed. Doesn't protect against remote attacks.
Important Note: Security often involves multiple layers (defense in depth). No single method is foolproof.