Computer Network

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🌐 Computer Network Basics

1. Definition

A computer network is a system of interconnected computers and devices that can communicate with each other and share resources like files, internet, printers, etc.

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🧱 Types of Networks

1. By Size

• PAN (Personal Area Network) – e.g., Bluetooth devices.

• LAN (Local Area Network) – e.g., home or office network.

• MAN (Metropolitan Area Network) – e.g., city-wide networks.

• WAN (Wide Area Network) – e.g., the internet.

2. By Topology

• Bus – All devices connected to a single cable.

• Star – Devices connected to a central hub.

• Ring – Devices in a circular loop.

• Mesh – Devices interconnected; used in robust systems.

• Hybrid – Combination of two or more topologies.

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📶 Network Components

• Router – Connects networks; routes traffic.

• Switch – Connects devices within a LAN.

• Hub – Simple version of a switch (less smart).

• Modem – Modulates/demodulates internet signals.

• Access Point – Provides wireless access.

• Firewall – Controls traffic based on rules.

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🔌 Network Media

• Wired: Ethernet cables (Cat5, Cat6), coaxial, fiber optics.

• Wireless: Wi-Fi, Bluetooth, infrared, microwave, satellite.

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📡 Communication Models

1. OSI Model (7 Layers)

1. Physical

2. Data Link

3. Network

4. Transport

5. Session

6. Presentation

7. Application

2. TCP/IP Model (4 Layers)

1. Network Interface

2. Internet

3. Transport

4. Application

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🌍 IP Addressing

• IPv4: 32-bit (e.g., 192.168.0.1)

• IPv6: 128-bit (e.g., 2001:0db8::1)

Types:

• Public vs. Private

• Static vs. Dynamic

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🔐 Network Security

• Protocols: SSL/TLS, IPsec

• Firewalls

• Antivirus/Anti-malware

• VPNs (Virtual Private Networks)

• IDS/IPS (Intrusion Detection/Prevention Systems)

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🔁 Common Protocols

• HTTP/HTTPS – Web browsing

• FTP/SFTP – File transfers

• SMTP/IMAP/POP3 – Email

• DNS – Domain name resolution

• DHCP – Dynamic IP assignment

• TCP/UDP – Core transport protocols

• ICMP – Used in ping/traceroute

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📈 Performance Metrics

• Bandwidth

• Latency

• Throughput

• Jitter

• Packet Loss

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⚙️ Advanced Topics

• Network Virtualization

• Cloud Networking

• SDN (Software-Defined Networking)

• QoS (Quality of Service)

• Network Monitoring Tools (e.g., Wireshark, Nagios)

• IoT Networking

• 5G and Edge Computing