A Level IT 9626 l Communication & Technology Part 1

Communication Technologies Overview
📌 Chapter 14 covers Communication Technologies, focusing on network types, characteristics, uses, advantages, and disadvantages.
📡 The core concept involves understanding data transmission from one place to another, necessitating the connection of computers to form a network.
💡 Networks are primarily established to share data and resources and facilitate communication between connected devices.

Network Fundamentals and Protocols
🌐 The discussion moves into network components, servers, cloud computing characteristics, and data transmission concepts like bandwidth and packet switching.
📜 The fundamental network model starts with the TCP/IP protocol and the OSI (Open Systems Interconnection) model, which outline standards for communication.
🔗 Both models utilize a layered structure to divide complex functionality into simpler, manageable sections for standardization.

OSI Model Layers
👩‍💻 The Application Layer is the top layer, directly interacting with user applications (like web apps, email clients) and managing protocols for meaningful data presentation.
🔏 The Presentation Layer handles data preparation, including translation, encryption, and compression to ensure data is understood by the receiving device.
🔗 The Session Layer is responsible for opening and closing communication links or channels between devices, managing the duration of the connection (session).
📦 The Transport Layer breaks down sessions into segments and is responsible for reassembling the final data packets upon arrival.
➡️ The Network Layer takes segments from the transport layer and breaks them down into small packets for transmission across networks.
🔗 The Data Link Layer has a similar role to the network layer but focuses on transmitting data from one computer to another within the same network segment.
🔌 The Physical Layer involves the physical equipment used to transmit the data.

Data Packets and Addressing
🧩 A packet is defined as a small unit of data in transmission, structured into three main parts: header, payload, and trailer.
📍 The Header contains critical addressing information, including the sender's/receiver's IP address and MAC address, and the sequence number.
✉️ The Payload contains the actual data to be transmitted, while the Trailer indicates the end of the packet and contains error-checking methods.
🏠 An IP address is assigned when connecting to the internet and can change, whereas a MAC address is a permanent identifier assigned by the manufacturer.

Circuit Switching vs. Packet Switching
📞 Circuit Switching requires a dedicated circuit or channel established before communication, meaning the channel remains dedicated and unavailable to others until the session ends (e.g., traditional phone systems).
📉 Circuit switching offers better quality and stability with low latency due to fixed bandwidth allocation, but bandwidth is inefficiently used.
🌐 Packet Switching is connectionless; data is broken into independent packets that travel individually via different routes, potentially arriving out of order.
⭐ Packet switching is more flexible (carrying video, web data, email) and is more efficient in using bandwidth by utilizing only what is needed, though this can result in higher latency.

Network Structures and Types
🤝 Peer-to-Peer (P2P) networks are decentralized, where connected computers have equal importance and no single server controls data sharing, making setup cheap and requiring little technical knowledge.
⚠️ A major disadvantage of P2P is the lack of central backup, meaning data loss if one computer fails, and performance can degrade if one peer is heavily accessed.
🏛️ The Client-to-Server model involves a centralized server providing services (e.g., File Server, Web Server, Mail Server) requested by clients, offering better security and centralized file backup.
❌ The main disadvantage of Client-to-Server is the high cost to set up, and the failure of the server results in loss of access to all files.
📍 LAN (Local Area Network) covers a geographically small area, while WAN (Wide Area Network) covers a wider range.
🔒 VPN (Virtual Private Network) encrypts data to access sensitive information remotely, securing identity, but its legality can be controversial in some countries.

Key Points & Insights
➡️ Network communication relies on defining rules using models like OSI (7 layers) and TCP/IP (4 or 5 layers), which share a common goal of layered, standardized function division.
➡️ Routers are responsible for sending data packets to destinations outside the current network, while switches use MAC addresses to direct data *within* the local network system.
➡️ When comparing data transfer methods, circuit switching guarantees quality for voice but wastes bandwidth; packet switching optimizes bandwidth use but introduces potential out-of-order arrival and higher latency.
➡️ For network architecture decisions, P2P is cheap and decentralized but lacks centralized security/backup, whereas Client-Server is secure and centralized but significantly more expensive to implement.

📸 Video summarized with SummaryTube.com on Jan 22, 2026, 13:53 UTC