TCP/IP Model in Computer Networks – Complete GATE Exam Notes by Vikash Yadav
Introduction
The TCP/IP (Transmission Control Protocol / Internet Protocol) model is the backbone of modern internet communication. It is a practical implementation model, unlike the OSI model, which is a reference framework.
For GATE Computer Science and Networking-related exams, understanding the TCP/IP model is essential, as many questions are based on its layers, functions, and comparison with OSI.
In this guide, Vikash Yadav explains the TCP/IP model in detail, focusing on exam-relevant points.
Overview of TCP/IP Model
- Developed by: DARPA (Defense Advanced Research Projects Agency) in the 1970s
- Purpose: Enable communication over ARPANET (precursor to the internet)
- Number of Layers: 4
- Type: Practical implementation model
Layers of the TCP/IP Model
The TCP/IP model consists of four layers:
| Layer No. | Layer Name | OSI Equivalent Layers | Function | Example Protocols |
|---|---|---|---|---|
| 4 | Application Layer | Application, Presentation, Session | User services and applications | HTTP, FTP, SMTP, DNS |
| 3 | Transport Layer | Transport | Reliable or fast data delivery | TCP, UDP |
| 2 | Internet Layer | Network | Logical addressing and routing | IP, ICMP, ARP |
| 1 | Network Access Layer | Data Link + Physical | Physical transmission and framing | Ethernet, Wi-Fi |
1. Application Layer
- Function: Provides network services to end-users.
- Examples: HTTP (web), SMTP (email), FTP (file transfer), DNS (domain name resolution).
- GATE Tip by Vikash Yadav: In TCP/IP, Presentation & Session layers are merged into Application Layer.
2. Transport Layer
- Function: Ensures data is delivered completely and correctly between applications.
- Protocols:
- TCP: Reliable, connection-oriented (used in HTTP, email).
- UDP: Fast, connectionless (used in streaming, gaming).
- Key Concepts: Port numbers, segmentation, error detection.
3. Internet Layer
- Function: Logical addressing (IP addresses) and routing.
- Protocols: IPv4, IPv6, ICMP, ARP.
- Role: Determines the best path for data packets to travel.
4. Network Access Layer
- Function: Handles physical transmission of data over a network.
- Protocols/Tech: Ethernet, Wi-Fi, PPP.
- Note: Combines OSI’s Data Link & Physical Layers.
TCP/IP Model Diagram
+-------------------+ (Application Layer)
+-------------------+ (Transport Layer)
+-------------------+ (Internet Layer)
+-------------------+ (Network Access Layer)
TCP/IP vs OSI Model
| Feature | OSI Model (7 Layers) | TCP/IP Model (4 Layers) |
|---|---|---|
| Layers | 7 | 4 |
| Developed By | ISO | DARPA |
| Approach | Theoretical | Practical |
| Presentation & Session Layers | Present separately | Merged into Application |
| Usage | Reference for networking | Actual internet model |
GATE Tip: Often, exam questions test layer mapping between OSI and TCP/IP.
Advantages of TCP/IP Model
- Works in real-world networks (internet).
- Flexible and scalable.
- Supports multiple routing protocols.
Disadvantages of TCP/IP Model
- Lacks clear separation of services like OSI.
- Not as descriptive for teaching as OSI.
GATE Exam Focus Points (By Vikash Yadav)
- Number of layers: 4 in TCP/IP.
- Layer mapping: OSI → TCP/IP mapping questions are common.
- Protocol identification: Example – HTTP → Application Layer.
- TCP vs UDP: Connection-oriented vs Connectionless.
- IP role: Logical addressing, packet forwarding.
Real-World Example
When you visit https://example.com:
- Application Layer: Browser sends HTTP request.
- Transport Layer: TCP ensures request is delivered correctly.
- Internet Layer: IP routes the request to the server.
- Network Access Layer: Ethernet or Wi-Fi transmits the data physically.
Conclusion
As Vikash Yadav summarizes, the TCP/IP model is the foundation of all internet communication. Understanding it deeply helps not only in academic exams like GATE, NET, and university courses, but also in practical networking jobs. Knowing how each layer functions makes it easier to troubleshoot, design, and optimize networks.