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A Computer Network is a collection of interconnected computing devices that can exchange data and share resources. Without networks, there would be no internet, email, video calls, or cloud storage.
Network Classifications by Area:
| Type | Range | Example | |---|---|---| | PAN (Personal Area Network) | ~10 meters | Bluetooth headphones | | LAN (Local Area Network) | Building/Campus | Home WiFi, office Ethernet | | MAN (Metropolitan Area Network) | City | Cable TV network | | WAN (Wide Area Network) | Country/Global | The Internet |
Network Topologies:
| Topology | Description | Advantage | Disadvantage | |---|---|---|---| | Bus | All devices on one cable | Simple, cheap | Single point of failure | | Star | All devices connect to central hub/switch | Easy to manage | Hub failure = network failure | | Ring | Devices connected in a circle | Orderly access | Any break stops network | | Mesh | Every device connects to every other | High reliability | Very expensive | | Hybrid | Combination of above | Flexible | Complex |
Key Network Devices:
The OSI (Open Systems Interconnection) Model is a conceptual framework that standardizes network communication into 7 layers.
Mnemonic: "All People Seem To Need Data Processing" (Application, Presentation, Session, Transport, Network, Data Link, Physical)
The TCP/IP Model is the practical model the internet uses. It has 4 layers (compared to OSI's 7).
| TCP/IP Layer | Equivalent OSI Layers | Protocols | |---|---|---| | Application | Application + Presentation + Session | HTTP, FTP, SMTP, DNS, DHCP | | Transport | Transport | TCP, UDP | | Internet | Network | IP, ICMP, ARP | | Network Access | Data Link + Physical | Ethernet, WiFi |
| Feature | TCP | UDP | |---|---|---| | Full Form | Transmission Control Protocol | User Datagram Protocol | | Connection | Connection-oriented (3-way handshake) | Connectionless | | Reliability | Reliable (acknowledgments) | Unreliable (no ACK) | | Order | Guaranteed in-order delivery | No order guarantee | | Speed | Slower | Faster | | Header Size | 20 bytes | 8 bytes | | Flow Control | Yes (sliding window) | No | | Error Check | Yes (checksum + retransmit) | Checksum only | | Use Cases | HTTP/S, Email, File transfer, SSH | Video streaming, Gaming, DNS, VoIP |
TCP 3-Way Handshake (Connection Establishment):
Client → Server: SYN (I want to connect)
Server → Client: SYN-ACK (OK, I'm ready)
Client → Server: ACK (Connection established!)
TCP 4-Way Termination:
Client → Server: FIN
Server → Client: ACK
Server → Client: FIN
Client → Server: ACK
An IP Address is a unique numerical identifier assigned to every device on a network.
192.168.1.100IPv4 Address Classes:
| Class | Range | Default Mask | Use | |---|---|---|---| | A | 1.0.0.0 – 126.255.255.255 | /8 | Large networks | | B | 128.0.0.0 – 191.255.255.255 | /16 | Medium networks | | C | 192.0.0.0 – 223.255.255.255 | /24 | Small networks | | D | 224.0.0.0 – 239.255.255.255 | — | Multicast | | E | 240.0.0.0 – 255.255.255.255 | — | Reserved/Research |
Private IP Ranges (RFC 1918 — not routable on internet):
10.0.0.0/8172.16.0.0/12192.168.0.0/16Special Addresses:
127.0.0.1 — Loopback (localhost)255.255.255.255 — Limited broadcast0.0.0.0 — Default routeSubnetting divides a large network into smaller subnetworks using a subnet mask.
Example:
IP Address: 192.168.1.0/24
Subnet Mask: 255.255.255.0
Network bits: 24 | Host bits: 8
Usable hosts: 2⁸ - 2 = 254
Network address: 192.168.1.0
Broadcast: 192.168.1.255
CIDR Notation: /24 means first 24 bits are network portion.
2001:0db8:85a3::8a2e:0370:7334HTTP Methods: GET, POST, PUT, DELETE, PATCH, HEAD
HTTP Status Codes:
| Code | Meaning | |---|---| | 200 OK | Request succeeded | | 201 Created | Resource created | | 301 Moved Permanently | Redirect | | 400 Bad Request | Client error | | 401 Unauthorized | Authentication required | | 403 Forbidden | Access denied | | 404 Not Found | Resource doesn't exist | | 500 Internal Server Error | Server-side error |
Static Routing: Manually configured routes. Simple, no overhead, not scalable.
Dynamic Routing: Routers exchange information to build routing tables automatically.
| Protocol | Type | Algorithm | Use | |---|---|---|---| | RIP | Distance Vector | Bellman-Ford | Small networks | | OSPF | Link State | Dijkstra | Large enterprise | | BGP | Path Vector | — | Internet backbone (between ISPs) | | EIGRP | Hybrid | DUAL | Cisco networks |
Common Attacks:
Security Mechanisms:
Complete Computer Networks notes for B.Tech ECE Semester 5 — OSI 7 layers, TCP/IP model, IP addressing, subnetting, HTTP, DNS, TCP vs UDP, and routing protocols.
56 pages · 2.8 MB · Updated 2026-03-11
OSI has 7 layers (theoretical reference model). TCP/IP has 4 layers (practical implementation model). TCP/IP is what the internet actually uses.
TCP is connection-oriented, reliable, ordered delivery with error checking. UDP is connectionless, faster but unreliable. TCP for web/email, UDP for video streaming/gaming.
Subnetting divides a large network into smaller subnetworks using a subnet mask. It improves security, reduces broadcast traffic, and uses IP addresses more efficiently.
DNS (Domain Name System) translates human-readable domain names (google.com) into IP addresses (142.250.182.206) that computers use to communicate.
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