Computer Networks
CN Part-1
- What is a Computer Network?
- Goals and Applications of Computer Networking
- Computer Network Components
- Types of Computer Networks
- Network Topology
- Difference between Client Server and Peer to Peer Network
- Layered Architecture in Computer Networks
- Protocol Hierarchy in Computer Networks
- Interfaces and Services in Computer Networks
- Connection Oriented and Connectionless Services
- Service Primitives
- OSI Model
- TCP/IP Model
- Difference between OSI Model and TCP/IP Model
- Encapsulation and Decapsulation in Computer Networks
- Queueing Models in Computer Network
CN Part-2
- Physical Layer in Computer Networks
- Transmission Media in Computer Networks
- Analog and Digital Signals
- Data Rate and Bandwidth
- Encoding Techniques
- Multiplexing in Computer Networks
- Transmission Modes in Computer Networks
- Data Link Layer
- Framing in Data Link Layer
- Flow Control in Data Link Layer
- Error Control in Data Link Layer
- Error Detection and Correction in Computer Networks
- Stop and Wait Protocol
- Sliding Window Protocol
- SDLC(Synchronous Data Link Control) Protocol
- High-Level Data Link Control (HDLC) Protocol
- Point-to-Point Protocol (PPP)
CN Part-3
- MAC Sublayer and MAC Addressing
- Channel Allocation Methods
- ALOHA Protocol (Pure and Slotted ALOHA)
- CSMA/CD and CSMA/CA in Computer Networks
- Ethernet (IEEE 802.3)
- Wireless LANs (IEEE 802.11, Wi-Fi, and Bluetooth Basics)
- Network Layer and Design Issues
- IPv4 and IPv6 Protocols
- Addressing: IP Address, Subnetting, and Supernetting
- Routing Algorithms: Static vs Dynamic, Distance Vector, and Link State
- Routing Protocols: RIP, OSPF, and BGP
- Packet Switching and IP Fragmentation
- Network Layer Protocols: ICMP, ARP, RARP, DHCP, and NAT
CN Part-4
- Transport Layer and Functions
- Process-to-Process Delivery, Ports, and Sockets
- TCP Segment and Three-Way Handshake Connection Establishment
- UDP (User Datagram Protocol): Format and Features
- Flow Control and Error Control in Transport Layer
- Congestion Control: Leaky Bucket, Token Bucket, and TCP Congestion Control
CN Part-5
- Application Layer Architecture and Principles
- Domain Name System (DNS)
- Email Protocols: SMTP, POP3, and IMAP
- File and Web Protocols: FTP, HTTP, and HTTPS
- Remote Access Protocols: Telnet and SSH
- World Wide Web (WWW) and Web Architecture
- Network Security Basics: SSL, TLS, and Cryptography Fundamentals
Ethernet (IEEE 802.3) in Computer Networks
Ethernet kya hai? (What is Ethernet?)
Ethernet duniya ki sabse popular aur widely used Wired Local Area Network (LAN) technology hai.
Ise 1970s mein Xerox PARC mein Robert Metcalfe ne develop kiya tha. Baad mein IEEE ne ise standardize kiya jise IEEE 802.3 Standard ke naam se jaana jaata hai.
Ethernet Physical Layer (Layer 1) aur Data Link Layer (Layer 2) ke protocols aur hardware standards (cables, connectors, NICs, switches) ko define karta hai.
Traditional Ethernet shared bus topology par CSMA/CD channel access method use karta tha. Modern Ethernet star topology aur Full-Duplex dedicated switches use karta hai jisme collisions nahi hote.
Evolution of Ethernet Generations
Speed aur transmission media ke according Ethernet char major generations mein evolve hua hai:
| Generation | Standard Speed | IEEE Standard | Common Media / Cable |
|---|---|---|---|
| Standard Ethernet | 10 Mbps | IEEE 802.3 | 10Base5 (Thick coax), 10Base2 (Thin coax), 10Base-T (Twisted pair) |
| Fast Ethernet | 100 Mbps | IEEE 802.3u | 100Base-TX (Cat5 UTP), 100Base-FX (Fiber optics) |
| Gigabit Ethernet | 1 Gbps (1000 Mbps) | IEEE 802.3z / 802.3ab | 1000Base-T (Cat5e/Cat6), 1000Base-SX/LX (Fiber optics) |
| 10-Gigabit Ethernet | 10 Gbps | IEEE 802.3ae | 10GBase-T (Cat6a), 10GBase-SR/LR (Single/Multi-mode Fiber) |
Ethernet Frame Format (IEEE 802.3)
Ethernet standard frame structure define karta hai jisme har packet ko pack kiya jaata hai:
| Preamble | SFD | Dest MAC | Src MAC | Type/Length | Data Payload + Padding | CRC (FCS) | | 7 Bytes | 1 Byte| 6 Bytes | 6 Bytes | 2 Bytes | 46 to 1500 Bytes | 4 Bytes |
| Field | Size | Purpose aur Description |
|---|---|---|
| Preamble | 7 Bytes | Alternating 1s aur 0s ka pattern (10101010...) jo sender aur receiver ke physical clocks ko synchronize karta hai. |
| SFD (Start Frame Delimiter) | 1 Byte | Pattern 10101011. Last ke do consecutive 11 bits receiver ko alert karte hain ki actual frame header agle byte se shuru ho raha hai. |
| Destination MAC | 6 Bytes (48 bits) | Receiving destination device ka physical MAC Address. |
| Source MAC | 6 Bytes (48 bits) | Sending device ka physical MAC Address. |
| Type / Length | 2 Bytes | Ethernet II mein yeh Network Layer protocol (e.g. 0x0800 for IPv4, 0x0806 for ARP) identify karta hai. IEEE 802.3 mein yeh payload length batata hai. |
| Payload (Data) | 46 – 1500 Bytes | Actual upper layer data packet (e.g. IP Packet). Minimum 46 bytes hona zaroori hai. Agar data 46 bytes se chota ho, toh extra zero bits (Padding) add karke 46 banaya jaata hai. |
| CRC (FCS) | 4 Bytes | 32-bit CRC checksum error detection ke liye. Corrupted frames ko receiver drop kar deta hai. |
Minimum and Maximum Frame Size in Ethernet
College semester exams mein yeh numerical question bohot common hai:
1. Minimum Frame Size: 64 Bytes
Destination MAC (6) + Source MAC (6) + Type (2) + Minimum Payload (46) + CRC (4) = 64 Bytes (512 bits).
64 bytes kyu? CSMA/CD collision detection rule ke according, sender ko collision detect karne ke liye kam se kam 2 * Tp time tak transmit karte rehna padta hai. Standard 10 Mbps Ethernet par 2.5 km max cable length mein 2 * Tp = 51.2 microseconds hota hai. 10 Mbps speed par 51.2 µs mein exactly 512 bits (64 Bytes) transmit hoti hain.
2. Maximum Frame Size: 1518 Bytes
Header + Trailer (18 Bytes) + Maximum Data (1500 Bytes) = 1518 Bytes.
(VLAN Tagging 802.1Q use hone par max size 1522 Bytes ho jaata hai).
Ethernet Cabling Standards (10Base5, 10Base2, 10Base-T)
Ethernet notation ko samajhna bohot aasan hai:
-> 10Base5 (Thicknet): 10 Mbps speed, Baseband signaling, Max 500 meters length per segment. Thick coaxial cable use karta tha.
-> 10Base2 (Thinnet): 10 Mbps speed, Baseband signaling, Max 185 (~200) meters length. Flexible thin coaxial cable with BNC connectors.
-> 10Base-T: 10 Mbps speed, Baseband signaling, ‘T’ stands for Twisted Pair Cable (Cat3/Cat5) with RJ-45 connectors. Modern star topology ka foundation isi se bana.
Advantages of Ethernet
-> High Reliability & Speed: Wireless ke comparison mein wired Ethernet bohot stable, low-latency, aur 10 Gbps+ speed support karta hai.
-> Cost Effective: Twisted pair cables aur Ethernet switches mass production ki wajah se bohot saste hote hain.
-> Backward Compatibility: Fast Ethernet, Gigabit Ethernet, aur 10G Ethernet ek dusre ke saath seamlessly negotiate (Auto-Negotiation) kar lete hain.
Summary Table
| Ethernet Parameter | Standard Value |
|---|---|
| Standard | IEEE 802.3 |
| Frame Size Range | Minimum: 64 Bytes | Maximum: 1518 Bytes (Payload: 46 – 1500 Bytes) |
| Addressing | 48-bit MAC Address (6 Bytes Source + 6 Bytes Destination) |
| Error Checking | 32-bit CRC (FCS) |