Study Material

  🔴 UNIT 5 – APPLICATION LAYER & NETWORK APPLICATIONS 🟦 1. Application Layer – Introduction ✅ Definition The Application Layer is the topmost layer of the OSI model. It provides services directly to the user . 👉 It acts as an interface between: User Network 🟦 2. Functions of Application Layer ✔ File transfer ✔ Email communication ✔ Remote login ✔ Web browsing ✔ Network management 🟦 3. Application Layer Protocols 🔹 1. FTP (File Transfer Protocol) Purpose: Used to transfer files between client and server. Features: ✔ Reliable ✔ Uses TCP ✔ Supports upload & download Ports: Port 21 → Control Port 20 → Data 🔹 2. TFTP (Trivial File Transfer Protocol) Features: ✔ Simpler than FTP ✔ Uses UDP ✔ No authentication ❌ Less secure 🔹 3. SMTP (Simple Mail Transfer Protocol) Purpose: Used to send emails Characteristics: ✔ Push protocol ✔ Works on TCP ✔ Port 25 🔹 4. POP3 (Post Office Protocol) Purpose: Used to receive email...

  🔴 UNIT 4 – TRANSPORT, SESSION & PRESENTATION LAYERS 🟦 PART A: TRANSPORT LAYER 1️⃣ Transport Layer – Introduction ✅ Definition The Transport Layer is responsible for: ✔ End-to-end communication ✔ Reliable data transfer ✔ Flow control ✔ Error control It works between: ➡ Application Layer and Network Layer 2️⃣ Functions of Transport Layer ✔ Segmentation & Reassembly ✔ Service point addressing (Port numbers) ✔ Flow control ✔ Error control ✔ Connection control 3️⃣ Transport Layer Protocols 🔹 1. TCP (Transmission Control Protocol) Features: ✔ Connection-oriented ✔ Reliable ✔ Error-free transmission ✔ Flow control ✔ Congestion control TCP Services: Sequencing Acknowledgment Retransmission Full-duplex communication TCP Header Contains: Source port Destination port Sequence number Acknowledgment number Flags Window size 4️⃣ TCP Connection Management 🔹 Three-Way Handshake 1️⃣ SYN → 2️⃣ SYN + ACK → 3️⃣ A...

  🔴 UNIT 3 – NETWORK LAYER 1️⃣ Network Layer – Introduction ✅ Definition The Network Layer is responsible for: Routing packets Logical addressing Path selection Congestion control 👉 It ensures data reaches the correct destination network . 2️⃣ Functions of Network Layer ✔ Logical addressing ✔ Routing ✔ Packet forwarding ✔ Congestion control ✔ Internetworking 3️⃣ Network Layer Services 🔹 Connection-Oriented Service Establishes connection before transmission Reliable Example: Virtual circuits 🔹 Connectionless Service No prior connection Fast but unreliable Example: Internet (IP) 4️⃣ Routing ✅ Definition Routing is the process of selecting the best path to transfer data from source to destination. 5️⃣ Types of Routing 🔹 1. Static Routing Fixed routes Manually configured Used in small networks 🔹 2. Dynamic Routing Routes change automatically Uses routing algorithms 6️⃣ Routing Algorithms 🔹 1....

  🔴 UNIT 2 – DATA LINK LAYER & MEDIUM ACCESS CONTROL 1️⃣ Data Link Layer – Introduction ✅ Definition The Data Link Layer is the second layer of the OSI model. It is responsible for reliable data transfer between two directly connected nodes . ✅ Main Functions ✔ Framing ✔ Error control ✔ Flow control ✔ Access control ✔ Physical addressing 2️⃣ Framing 🔹 Definition Framing divides the data stream into manageable units called frames . 🔹 Methods of Framing 1. Character Count Frame size specified in header ❌ Error-prone 2. Byte Stuffing Special character added to data ✔ Used in HDLC 3. Bit Stuffing Extra bit inserted after 5 consecutive 1s ✔ Used in modern networks 3️⃣ Error Detection Techniques 🔹 1. Parity Check Adds 1 parity bit Detects single-bit error 🔹 2. Checksum Sum of data bits Used in TCP/IP 🔹 3. Cyclic Redundancy Check (CRC) Most powerful method Uses polynomial division ✔ Highly reliable ✔ Wi...

  📘 PAPER 6 – DATA COMMUNICATION & NETWORKS 🔴 UNIT 1 – INTRODUCTION & PHYSICAL LAYER 1️⃣ Introduction to Data Communication ✅ Definition Data Communication is the process of transferring data from one device to another using a transmission medium. Components of Data Communication Sender Receiver Message Transmission Medium Protocol Characteristics of Data Communication ✔ Delivery ✔ Accuracy ✔ Timeliness ✔ Jitter-free communication 2️⃣ Goals of Computer Networks ✔ Resource sharing ✔ Communication ✔ Reliability ✔ Cost reduction ✔ Scalability 3️⃣ Network Structure & Architecture Network Architecture: Defines how network is designed and how devices communicate. 4️⃣ OSI Reference Model OSI has 7 Layers Layer Name Function 7 Application User interface 6 Presentation Encryption 5 Session Session control 4 Transport Reliable delivery 3 Network Routing 2 Data Link Framing 1 Physical Transmission 👉 Exam Tip: Remember as: A-P-S-...