AEAIT Task 8 Cheatsheet

15/06/2026

AEAIT Task 8 Cheatsheet

Brief Overview & Key Points

Definition, benefits, and drawbacks of computer networks.
Detailed look at network types, media (fiber, copper, wireless) and their characteristics.
Overview of core devices such as NICs, switches, routers, firewalls, and access points.
Introductory guide to the OSI layers and IPv4/IPv6 addressing basics.

📡 Definition & Applications

Definition: A computer network is the interconnection of two or more computers to enable communication and resource sharing.

Applications

Sharing printers, scanners, and other hardware.
Accessing expensive software and databases centrally.
Sending messages and files between computers.
Exchanging data across geographically distant sites.
Providing internet connectivity for homes and businesses.

💡 The diagram visualizes the hierarchical relationship among PAN, LAN, MAN, CAN, and WAN, illustrating how each network type fits within the overall concept of a “NETWORK.”

🖥 Components of a Computer Network

Hardware

Two or more computers (hosts)
Transmission media (cables, fiber, wireless links)
Network Interface Card (NIC) – provides the physical connection point

The NIC’s green circuit board and Ethernet port illustrate the interface through which a computer joins the network.

Switches, routers, firewalls, and modems

Software

Operating system (OS) with networking stack
Network management and security utilities

📈 Network Benefits

Category	Example Benefits
Sharing	Centralized printers, storage, and applications reduce duplicate hardware.
Connectivity	Real‑time communication, remote access, and Internet services.
Additional Advantages	Faster data exchange, lower overall cost, improved security, centralized software updates, email, flexible access.

⚖ Disadvantages of Networks

High initial cost for installation and equipment.
Ongoing administrative overhead (maintenance, updates).
Single points of failure (e.g., server or cable faults) can disrupt service.
Potential for security breaches if not properly protected.

🌐 Classification by Geographic Area

Network Type	Typical Scope	Typical Media	Example Use
PAN (Personal Area Network)	One person’s devices	Bluetooth, short‑range Wi‑Fi	Phone ↔ earbuds
LAN (Local Area Network)	Office, school, building	Ethernet, Wi‑Fi	School computer lab
CAN (Campus Area Network)	University campus	Fiber, switches, routers	Campus-wide file server
MAN (Metropolitan Area Network)	City‑wide	Fiber, coaxial	City‑wide cable TV/Internet
WAN (Wide Area Network)	Global / Internet	Satellite, leased lines, fiber	The Internet

📡 LAN (Local Area Network)

Designed for small physical areas (office, factory, building).
Topologies supported: star, bus, ring, tree.
Usually privately owned and managed.

Example diagram showing a router, switch, and wireless access point: The image illustrates how a router connects to a switch, which then serves both wired desktops and a wireless access point for laptops and phones.

🌍 WAN (Wide Area Network)

Connects geographically separated sites via leased telephone lines, satellite links, or fiber.
Enables large‑scale data transfer across cities or continents.
Typically public or shared infrastructure (e.g., the Internet).

📱 PAN (Personal Area Network)

Centered on an individual; links devices like smartphones, tablets, laptops, and wearables.
Can be wired (USB) or wireless (Bluetooth, Wi‑Fi Direct).

🏫 CAN (Campus Area Network)

Interconnects multiple LANs within a limited area (university, corporate campus).
Uses high‑capacity switches, routers, and often fiber for backbone connections.

🏙 MAN (Metropolitan Area Network)

Bridges the gap between LAN and WAN; serves an entire city.
Often built with optical fiber and can function as a single service provider network (e.g., city‑wide broadband).

🔀 Network Classification by Component Role

Model	Description	Typical Use
Peer‑to‑Peer (P2P)	Every node acts as both client and server; resources are shared directly.	Home file sharing, small study groups.
Client‑Server	Dedicated servers provide resources; clients request services.	Enterprise file servers, online services (email, web).

🤝 Peer‑to‑Peer Networks

Advantages:
Low cost (no dedicated server hardware).
Simple administration; each user controls their own machine.
Built‑in redundancy — failure of one node doesn’t collapse the whole network.
Disadvantages:
Limited security; each computer manages its own protection.
No central storage; data is scattered across devices.
Version‑control issues and higher load on individual PCs.

🏢 Client‑Server Networks

Advantages:
Centralized security and administration.
Better performance; servers handle intensive tasks.
Centralized backup and reliability.
Disadvantages:
Requires professional IT staff for setup/maintenance.
Higher hardware and software costs (powerful servers, licenses).

🗄 Types of Servers

Server Type	Primary Function	Typical Example
File server	Stores and manages files for users.	School server for student assignments.
Print server	Queues and controls printing jobs.	Office shared‑printer system.
Application server	Hosts software applications centrally.	Company‑wide Microsoft Office suite.
Message server	Handles email, chat, and other communications.	Gmail/Outlook mail server.
Database server	Manages large structured data sets.	Bank customer‑record database.

📡 Transmission Media Overview

1️⃣ Optical Fibre Cable

Structure: Core, cladding, buffer, jacket.

The layers illustrate how light is guided through the core while the cladding prevents signal loss.

How it works: Data → light pulses → travel through core → cladding reflects → reconverted to data.
Pros: Very high speed, huge bandwidth, immune to EMI, low attenuation.
Cons: Expensive installation, fragile, difficult to splice.

2️⃣ Twisted Pair Cable (Ethernet)

Structure: Four twisted copper pairs; some variants add foil shielding.

The diagram shows the conductor, insulation, braid shield, and outer jacket that protect the twisted pairs.

Categories:
Cat 5: up to 100 Mbps, 90 m max.
Cat 6: up to 1 Gbps, 90 m max.
Pros: Cheap, easy to install, widely supported.
Cons: Limited distance, vulnerable to EMI compared to fiber.

3️⃣ Coaxial Cable

Structure: Central conductor, insulating layer, braided shield, outer jacket. (No dedicated image provided, but description aligns with the cable component diagram.)
Performance: ≈ 10 Mbps, up to 180 m.
Pros: Better shielding than basic twisted pair.
Cons: Lower speed, bulkier, largely obsolete for new LANs.

4️⃣ Wireless (Wi‑Fi)

Radio‑frequency (RF) bands: 2.4 GHz (longer range, more interference) vs 5 GHz (higher speed, shorter range).
Key device: Wireless Access Point (WAP) – bridges wired backbone to wireless clients.

The diagram shows a central router distributing Wi‑Fi to laptops, phones, and printers.

Pros: No cabling, mobility, easy deployment.
Cons: Less secure, subject to interference, performance drops with distance.

5️⃣ Bluetooth

Frequency: 2.45 GHz, range ≤ 10 m.
Typical uses: Headsets, keyboards, IoT devices.
Pros: Low power, simple pairing.
Cons: Low data rates, short range.

📊 Comparison of Transmission Media

Medium Type	Speed	Max Distance	Interference	Cost
Optical Fibre (Wired / light)	Very high	Very long (city/continent)	None	High
Twisted Pair (Cat 5) (Wired)	Up to 100 Mbps	Up to 90 m	Moderate	Low
Twisted Pair (Cat 6) (Wired)	Up to 1 Gbps	Up to 90 m	Moderate (better shielding)	Medium
Coaxial (Wired)	10 Mbps	Up to 180 m	Low	Medium
Wireless Wi‑Fi (Wireless)	High (varies)	20 – 100 m	Moderate	Low
Bluetooth (Wireless)	Low	≤ 10 m	Moderate	Low

⚡ Ethernet vs. Wi‑Fi (Feature Comparison)

Feature	Ethernet (Wired)	Wi‑Fi (Wireless)
Connection type	Physical cable	Radio waves
Speed	Faster, less loss	Typically slower, variable
Security	More secure (requires physical access)	Less secure (air‑borne signals)
Interference	Minimal (shielded)	Susceptible to walls, devices
Installation	Requires cabling	No cables, plug‑and‑play
Stability	Highly stable	Drops possible
Mobility	Limited (fixed cable)	High – move freely

📚 Key Terms

Term	Definition
Transmission	Movement of data between devices.
Upload	Sending data from a local device to a remote server.
Download	Receiving data from a remote source to a local device.
Ethernet	Wired networking using twisted‑pair cables and RJ‑45 connectors.
Wi‑Fi	Wireless networking using radio frequencies.
Optical Fibre	Light‑based cable for high‑speed, long‑distance communication.
RJ‑45	Standard connector for Ethernet cables.
WAP	Wireless Access Point, bridges wired and wireless networks.
Bluetooth	Short‑range wireless protocol for low‑data‑rate devices.
Attenuation	Loss of signal strength over distance.
EMI	Electromagnetic interference that can degrade signal quality.

🔌 Network Interface Card (NIC)

What is a NIC?

Definition: A Network Interface Card (NIC) is a hardware component that provides the physical and data‑link connection between a computer and a network.

Parallel ↔ Serial Conversion

Inside the host: Data moves in parallel (multiple bits simultaneously on separate bus lines).
Across the network: Data travels in serial form (one bit at a time) over the transmission medium.
The NIC converts parallel data to serial for transmission and reconverts received serial data back to parallel for the host.

OSI Layers Involved

Physical Layer (Layer 1): Handles the electrical/optical signals on the medium.
Data Link Layer (Layer 2): Manages MAC addressing and frame framing.

Types of NICs

Media	Example NIC
Ethernet (Copper)	RJ‑45 NIC for twisted‑pair cables
Fiber Optic	SFP or SFP+ module
Wireless (Wi‑Fi)	Integrated 802.11ac/ax adapter
Specialized	Token Ring, FDDI, or ATM NICs

📡 Core Network Devices

🔹 Hub

Function: Receives a signal on one port and broadcasts it to every other port (layer 1 device).
Drawbacks:
Generates unnecessary traffic.
No MAC address filtering → security risk.
Limited to 10 Mbps/100 Mbps speeds.
Status: Largely replaced by switches.

🔹 Switch

Operation: Reads the destination MAC address, looks it up in its CAM (Content‑Addressable Memory) table, and forwards the frame only to the appropriate port (layer 2 device).
Learning Process:

Receives a frame.
Stores the source MAC ↔ port mapping.
Uses the table for subsequent forwarding.

Advantages:
Reduces collisions and traffic.
Supports full‑duplex communication.
Typical speeds: 1 Gbps (Fast Ethernet) up to 10 Gbps (10 GbE).
ASICs: Application‑Specific Integrated Circuits enable hardware‑level frame processing, achieving millions of frames per second.

🔹 Router

Primary Role: Connects different networks (e.g., LAN ↔ WAN) and determines the optimal path for packets (layer 3).
Key Components:
Routing Table: Stores network prefixes, next‑hop addresses, and interface metrics.
Routing Protocols: OSPF, RIP, EIGRP, BGP (dynamic table updates).
Routing Process:

Packet arrives → read destination IP.
Lookup longest‑prefix match in routing table.
Forward to the selected next‑hop interface.

Static vs Dynamic:
Static routes are manually configured.
Dynamic routes are learned automatically via protocols.

🔹 Modem

Full Form: Modulator‑Demodulator.
Function: Converts digital data from a host into an analogue signal for transmission over telephone lines (or vice‑versa).
Key Converters:
DAC (Digital‑to‑Analogue Converter) – digital → analogue.
ADC (Analogue‑to‑Digital Converter) – analogue → digital.
Modern Trend: Broadband and fiber networks often skip traditional modems, using pure digital transport (e.g., FTTH).

🔹 Firewall

Purpose: Enforces security policies by monitoring and filtering inbound/outbound traffic.
Types:
Hardware firewall – placed at the network perimeter.
Software firewall – runs on individual hosts (e.g., Windows Defender).
Operation Modes: Packet‑filtering (checks headers), stateful inspection (tracks connection states), and application‑layer filtering (examines payload).

📶 Wireless Access Point (WAP) vs. Wi‑Fi Router

Feature	WAP	Wi‑Fi Router
Core Function	Bridges wired LAN to wireless clients.	Combines routing, NAT, DHCP, and WAP functions.
Typical Placement	Inside an existing LAN, managed by a separate router.	Edge of the network, directly connects to ISP.
Management	Often a stand‑alone device; no NAT.	Provides Internet sharing (NAT) and DHCP.

🌉 Bridge

Layer: Operates at Data Link (Layer 2).
Function: Connects two LAN segments, forwarding frames based on MAC address filtering.
Types: Local Bridge, Transparent Bridge, Source‑Routed Bridge, Remote Bridge, Wireless Bridge.
Current Status: Superseded by switches, which provide faster, full‑duplex bridging with built‑in learning.

🌐 Gateway

Definition: A gateway translates and forwards traffic between networks that use different protocols or different layer‑3 addressing schemes.
Common Roles: Email gateway (SMTP ↔ X.400), Protocol gateway, Internet gateway.
Distinct from Router: A router forwards packets with the same protocol; a gateway performs protocol conversion.

🛡 Proxy Server

Function: Acts as an intermediate for client requests to external servers.
Benefits: Security (masks internal IPs), Caching (reduces bandwidth), Filtering (enforces policies).
Workflow: Client → Proxy request → Proxy fetches resource from target server → Proxy returns data to client.

📡 Transceiver

Definition: A device that both transmits and receives signals.
Typical Locations: Integrated into NICs or separate modules (e.g., SFP transceiver for fiber).
Conversion Role: Handles digital‑to‑analogue and analogue‑to‑digital conversion when the medium requires a different signal type.

📜 OSI Model Overview (Simplified)

Layer	Primary Responsibility	Typical Devices/Protocols
7 – Application	User‑level services (email, web)	Browsers, mail clients
6 – Presentation	Data translation, encryption, compression	SSL/TLS, JPEG, MP3
5 – Session	Session establishment & management	RPC services
4 – Transport	End‑to‑end reliability (TCP) or low‑latency (UDP)	OS kernels, firewalls
3 – Network	Routing, IP addressing	Routers, layer‑3 switches
2 – Data Link	Frame framing, MAC addressing, error detection	Switches, bridges
1 – Physical	Bit‑level transmission (cabling, signaling)	NIC, repeaters, hubs

The OSI model provides a conceptual framework for how data moves from a source application to a destination application across a network.

🌐 IP Addressing Basics

IPv4

Format: a.b.c.d (each octet 0‑255).
Example: 192.168.1.1 – common private‑network gateway address.
Address Classes: A (large networks), B (medium), C (small).
Subnetting: Divides a network into smaller sub‑nets using a netmask (e.g., /24 = 255.255.255.0).

IPv6

Format: Eight groups of four hex digits (xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx).
Example: 2001:0db8:85a3::8a2e:0370:7334.
Advantages: Vast address space, built‑in stateless address autoconfiguration, and simplified header for routing.

IPv6 is designed to replace IPv4 as the global internet grows, offering better scalability and security features.

📦 Summary of Key Network Devices

Device	Layer	Core Function
NIC	1‑2	Physical connection & MAC framing
Hub	1	Broadcasts incoming signal to all ports
Switch	2	Forwards frames based on MAC address
Router	3	Determines best path using IP routing
Modem	1‑2	Converts digital ↔ analogue for legacy lines
Firewall	3‑4	Filters traffic per security policies
WAP	1‑2	Provides wireless connectivity
Bridge	2	Links LAN segments, filters traffic
Gateway	3 + (translation)	Translates between different protocols
Proxy	7	Interposes between client and external server
Transceiver	1	Sends and receives signals across media

📊 Quick Comparison: Switch vs. Router vs. Bridge

Feature	Switch	Router	Bridge
OSI Layer	2	3	2
MAC vs. IP	Forwards by MAC address	Forwards by IP address	Forwards by MAC address
Network Segmentation	Creates separate collision domains	Connects different IP networks	Merges two LAN segments
Typical Speed	Up to 10 Gbps (modern)	Up to 1 Gbps (enterprise)	Up to 100 Mbps (legacy)
Intelligent Features	VLANs, port security, STP	NAT, DHCP, ACLs, routing protocols	Minimal; basic filtering only

🛠 Practical Tips for Network Troubleshooting (Brief)

Check physical connectivity – Verify NIC LEDs, cable integrity, and patch‑panel connections.
Validate IP configuration – ipconfig /all (Windows) or ifconfig (Linux) to confirm correct IPv4/IPv6 settings.
Ping test – ping measures basic latency and confirms reachability.
Trace route – tracert (Windows) / traceroute (Linux) shows each hop and identifies possible bottlenecks.
Inspect switch MAC table – show mac address-table (Cisco) to see where a MAC address is learned.
Review firewall logs – Look for blocked packets or unexpected drops.

End of Section 2.

🔐 Proxy Servers – Usage Context

Proxy Server: A network intermediary that receives client requests, forwards them to external servers, and returns the responses, often adding caching, filtering, or anonymity.

Common deployment sites

🏫 Schools – monitor web usage and enforce content policies.
🏢 Workplaces – protect corporate data and reduce bandwidth consumption.
🏛 Organizations – filter or log traffic for security compliance.

🖥 Servers – Roles & Types

Server: A computer that provides resources, data, or services to other computers (clients) over a network.

📂 What Is a Server?

Hardware profile – typically larger storage capacity, more RAM, and faster CPUs than standard workstations.
Functionality – determined by the services it hosts (file sharing, printing, web hosting, etc.).
Network context – behavior varies with the network architecture (peer‑to‑peer, client‑server, etc.).

🔄 Peer‑to‑Peer vs. Client/Server

Architecture	Role of Each Machine	Typical Scale	Advantages	Disadvantages
Peer‑to‑Peer (P2P)	Every workstation can act as both client and server.	Small offices, homes.	Low cost, easy setup, built‑in redundancy.	Limited security, scattered data, harder to manage.
Client/Server	Dedicated servers provide services; clients request them. Multiple servers can exist but do not function as workstations.	Most corporate environments.	Centralized control, stronger security, easier backup.	Higher hardware cost, requires IT staff.

📡 Specialized Servers

DNS Server: Resolves domain names to IP addresses. (e.g., Internet Service Provider’s name resolver.)
Web Server: Hosts websites and serves HTTP/HTTPS content. (e.g., Apache or Nginx serving a company portal.)
Mail Server: Manages email transmission and storage (SMTP/IMAP/POP). (e.g., Corporate Exchange or Gmail server.)

🗺 Network Design Exercise (10 marks)

Task: Produce a logical LAN‑to‑WAN layout for a small accounting firm, showing all required devices and the correct order of connections from the ISP to end devices. Use solid lines for wired links and dashed lines for wireless links.

📦 Equipment List

Quantity	Device	Connection Type
3	Desktop computers	Wired
1	File server	Wired
1	Network printer	Wireless
2	Laptops	Wireless
2	Tablets	Wireless
1	Switch	Wired
1	Router	Wired
1	Modem	Wired
1	Firewall	Wired
1	Wireless Access Point (WAP)	Wireless
1	Smart TV	Wireless
1	ISP / NBN cloud	–

🖼 Recommended Layout (textual diagram)

[ ISP / NBN Cloud ]
       │
    (solid) ──> [ Modem ]
                   │
                (solid) ──> [ Firewall ]
                               │
                            (solid) ──> [ Router ]
                                           │
                               ┌───────────┴───────────┐
                               │                       │
                            (solid)                 (solid)
                               │                       │
                           [ Switch ]       [ Wireless Access Point ]
                               │                       │
                 ┌─┼─┬─┬─┬─┐   └─┬─┬─┬─┬─┬─┘
                 │ │ │ │ │ │             │ │ │ │ │ │
                 │PC│PC│PC││             │Laptop│Tablet│ Smart TV │
                 │ │ │ │ │ │             │     │      │          │
                 │File Server│           │   Network Printer     │
                  ( wired )                   ( wireless )

Explanation of the flow

Internet entry – The ISP cloud connects to the modem (solid line).
Security perimeter – The modem feeds the firewall, which filters inbound/outbound traffic.
Routing – The firewall passes traffic to the router; the router performs NAT and directs traffic to the internal LAN.
Wired distribution – From the router, a switch provides dedicated Ethernet ports for all wired devices (desktop PCs and the file server).
Wireless distribution – The router also connects (solid line) to the Wireless Access Point; the WAP broadcasts Wi‑Fi to laptops, tablets, the smart TV, and the network printer (all shown with dashed lines).

Solid lines = Ethernet or other wired media (e.g., Cat 6).
Dashed lines = Wireless links (Wi‑Fi).

The diagram satisfies the requirement to label each device, display the correct order from ISP to end devices, and distinguish wired versus wireless connections.

📚 Quick Recap – Key Points

Proxy servers are placed to filter or cache traffic, while dedicated servers (file, DNS, web, mail) host specific services.
Network design for mixed wired/wireless environments follows a clear hierarchy: ISP → Modem → Firewall → Router → (Switch ↔ WAP) → End devices.