Study sheet: Computer Networking Fundamentals

📋 Course Outline

1. Network Concepts and Devices
2. Communication Elements and Modes
3. Transmission Media
4. Network Devices and OSI Layers
5. Switching and Packet Delivery
6. Network Topologies and Types
7. Delay, Throughput, and Performance
8. OSI and TCP/IP Models

📖 1. Network Concepts and Devices

🔑 Key Concepts & Definitions

• Computer network : A set of interconnected devices that communicate and share data through communication links.
• Network protocol : A set of rules that specifies data format, exchange, error checking, addressing, and delivery between communicating devices.

★ Must-know

📌 End devices generate or consume data, whereas intermediary devices connect networks and forward data between end devices.

Further detail

• Examples of the two device categories include: computers, smartphones, laptops, switches, hubs, routers, firewalls

💡 Memory Hook

End devices create or consume data; intermediary devices forward it.

📖 2. Communication Elements and Modes

🔑 Key Concepts & Definitions

• Data communication : The exchange of data between devices through a transmission medium.

★ Must-know

📌 Simplex communication is one-way only, half-duplex communication is two-way but only one direction at a time, and full-duplex communication is simultaneous in both directions.

Further detail

• A telephone is an example of full-duplex communication, while radio broadcasting is an example of simplex communication.

💡 Memory Hook

Sender → transmitter → medium → receiver → destination

📖 3. Transmission Media

★ Must-know

• Examples of guided media include:

  • twisted-pair cable
  • coaxial cable
  • optical fiber

• Optical fiber transmits data as light signals and provides high bandwidth over long distances.

Further detail

• Examples of unguided media include:
  • radio waves
  • microwaves
  • infrared
  • Bluetooth
  • satellite communication

💡 Memory Hook

Guided media use cables, whereas unguided media use electromagnetic waves.

📖 4. Network Devices and OSI Layers

★ Must-know

• A hub operates at the Physical layer and broadcasts an incoming signal to its ports.

• A switch operates at the Data Link layer and forwards frames using MAC addresses.

• A router operates at the Network layer and forwards packets between different networks using routing decisions.

Further detail

• A modem converts signals between forms suitable for a computer network and a transmission medium.

💡 Memory Hook

Physical → Data Link → Network → Transport → Session → Presentation → Application

📖 5. Switching and Packet Delivery

★ Must-know

📌 Circuit switching establishes a dedicated path before transmission and keeps that path for the communication session.

📌 Packet switching divides data into packets that are forwarded independently through shared network links.

Further detail

• Datagram packet switching does not establish a connection before transmission, whereas virtual-circuit packet switching establishes a logical connection before sending packets.

💡 Memory Hook

Circuit switching reserves a path; packet switching shares links dynamically.

📖 6. Network Topologies and Types

★ Must-know

📌 A LAN covers a limited local area, a MAN covers a metropolitan area, and a WAN covers a wide geographic area.

Further detail

• A LAN commonly connects devices within a building or campus, while a WAN can connect networks across cities or countries.

📖 7. Delay, Throughput, and Performance

🔑 Key Concepts & Definitions

• Throughput : The rate at which data is successfully delivered from source to destination.

📝 Essential Points

📐 Formula — Total nodal delay is the sum of transmission delay, propagation delay, processing delay, and queuing delay: $T=T_{t}+T_{p}+T_{pr}+T_{q}$.

📐 Formula — Transmission delay is the time required to place all packet bits onto the link and is calculated as $T_t=\frac{L}{R}$, where L is packet length and R is transmission rate.

📐 Formula — Propagation delay is the time required for a signal to travel across the link and is calculated as $T_p=\frac{d}{s}$, where d is distance and s is propagation speed.

💡 Memory Hook

Transmission + propagation + processing + queuing = total delay

📖 8. OSI and TCP/IP Models

📝 Essential Points

• The seven OSI layers are:

  • Physical
  • Data Link
  • Network
  • Transport
  • Session
  • Presentation
  • Application

• The Physical layer transmits raw bits, the Data Link layer frames data and uses MAC addressing, and the Network layer routes packets between networks.

• The Transport layer provides end-to-end delivery, while the Application layer supports network applications and protocols such as HTTP, FTP, DNS, and SMTP.

📌 TCP is connection-oriented and reliable, whereas UDP is connectionless and does not provide the same reliability mechanisms.

💡 Memory Hook

OSI is a seven-layer reference model; TCP/IP is the practical protocol suite.

📊 Synthesis Tables

Network Device Comparison

Device	Main layer	Main function
Hub	Physical	Broadcasts incoming signals
Switch	Data Link	Forwards frames using MAC addresses
Router	Network	Forwards packets between networks
Modem	Physical	Converts signals