TCP and UDP

TCP (Transmission Control Protocol)

TCP stands for Transmission Control Protocol.
It is a connection-oriented protocol that allows devices to communicate reliably over a network.

Key Features of TCP

• Ensures data reaches the destination correctly

• Maintains correct order of data

• Detects and retransmits lost packets

• Works well even when the network is slow or unreliable

Used : Web browsing, emails, file transfers.

TCP 4-Layer Model

The TCP/IP model is a 4-layer networking model used in real-world internet communication.

1. Application Layer

Purpose:
Allows users to interact with network-connected applications.

Functions:

• Data formatting

• Application-level communication

Protocols:

• HTTP / HTTPS – Web

• SMTP – Email

• FTP – File transfer

2. Transport Layer

Purpose:
Manages end-to-end communication between devices.

Functions:

• Data segmentation

• Port addressing

• Flow control and reliability

Protocols:

• TCP – Reliable, ordered delivery

• UDP – Fast, best-effort delivery

3. Internet Layer

Purpose:
Responsible for logical addressing and routing across networks.

Functions:

• Assigns IP addresses

• Routes packets between networks

Protocols:

• IP (IPv4 / IPv6)

• ICMP

4. Network Access Layer

Purpose:
Handles physical data transmission over the network.

Functions:

• Frame creation

• MAC addressing

• Signal transmission

Technologies:

• Ethernet

• Wi-Fi

• ARP

UDP

UDP stands for User Datagram Protocol.
It is a connectionless transport-layer protocol that focuses on speed rather than reliability.

How UDP Works

• No connection setup before sending data

• Sends data as independent datagrams

• No acknowledgment from receiver

• No retransmission of lost packets

UDP simply sends data and does not check whether it arrives.

Key Features of UDP

• No guarantee of delivery

• No error correction or packet reordering

• Very low overhead

• Faster than TCP

Where UDP is Used

UDP is used where real-time speed is more important than accuracy:

• Video streaming

• Online gaming

• Video calls (VoIP)

• DNS

Example:
In a video call, if one packet is lost, UDP does not resend it—the call continues smoothly.

Key differences between TCP and UDP

Uses of TCP vs UDP in real-world

Every message must arrive correctly | Live Streaming
Small losses are okay, speed matters | | File Transfers
No missing or corrupted data allowed | Online Gaming
Low latency is more important than perfection | | Web Browsing (HTTP/HTTPS)
Pages must load completely and correctly | Video Chat / Voice Calls
Smooth, real-time communication |

HTTP

HTTP (Hypertext Transfer Protocol) is a foundational application-layer protocol used for transmitting web data such as HTML, images, CSS, and JSON across the Internet. It operates using a client–server model, where a browser (client) sends an HTTP request and the server responds with the requested resource.

HTTP follows a stateless request–response mechanism, meaning each request is independent.

HTTP is the language your browser uses to talk to websites.

When you open a website:

• Your browser asks for a page

• The server replies with the page

That asking and replying happens using HTTP.

Common HTTP Methods

• GET: Retrieves data.

• POST: Submits data to be processed.

• PUT/DELETE: Modifies or removes data.

Typical Status Codes

• 200: OK (Success).

• 301: Moved Permanently.

• 404: Not Found.

• 500: Internal Server Error.

HTTP vs. TCP

HTTP (Hypertext Transfer Protocol) and TCP (Transmission Control Protocol) are both used to transfer data over the internet, but they serve different roles. They work closely together, yet they are not the same thing.

Key Differences Between HTTP and TCP

How HTTP and TCP Work Together

1. Browser wants a webpage

2. HTTP creates a request

3. TCP establishes a connection

4. TCP delivers the HTTP request safely

5. Server sends HTTP response

6. TCP delivers it back correctly

HTTP talks, TCP delivers.

Simple Analogy

• HTTP = What you say in a phone call

• TCP = The phone network that makes sure your voice reaches clearly