The internet is just millions of computers talking to each other
But data doesn’t travel as one big piece—it’s broken into small packets and sent across many networks.

So we need rules (protocols) to decide:

1. How to send data

2. How fast to send it

3. What to do if something is lost

4. How to put data back in order

That’s where TCP and UDP come in. They are transport layer protocols—their job is to move data from one computer to another

TCP

TCP is connection-oriented protocol. Before any data is sent, the sender and receiver must perform a three-way handshake to establish a connection.

Advantages of TCP ➼

• Reliability: It gurantees that data reaches the destination in the corect order. If a packet is lost, TCP detects it and retransmits the data.

• Flow Control: It manages the speed of data transmission to ensure the receiver isn't overwhelmed.

•Error Checking: It performs extensive checks to ensure data hasn't been corrupted

USES ➼

•Web-Browsing(HTTP,HTTPS)

•Emails(SMTP)

•File Transfers(FTP)

UDP

UDP is connectionless Protocol. It simply sent packets at the destinaton witout checking if the receiver is ready or if the data actually arrived

Advantages of UDP ➼

• Speed: Because there is no handsake and no retansmission of lost packet, it is significantly faster and has lower latency than TCP.

• No Guarantees: Data can arive out of order, or not at all. There is no acknowledgment sent back to the sender.

• Lightweight: It has a very small header size (8 bytes) compared to TCP (20 bytes).

USES ➼

• Online Gaming

• Live Streeming

• Dns Lookups

TCP = Courier / Careful Phone Call (Safe & Reliable)

Think of TCP like sending a package by a trusted courier:

1. You book the courier first (connection is made)

2. The courier confirms delivery

3. If the package is lost or damaged, it is sent again

4. Packages are delivered in the correct order

5. This takes a bit more time, but it’s safe

like a proper phone call:

1. You first check: “Hello, can you hear me?”

2. If the line is bad, you repeat what you said

3. You make sure the other person understood

4. Slower, but reliable communication

UDP = Live Announcement / Live Broadcast (Fast but Risky)

Think of UDP like a live announcement on a loudspeaker or live TV broadcast:

1. You just speak/send — no setup

2. You don’t know if everyone heard it

3. If someone misses a word, you don’t repeat it

4. Some people may hear parts out of order or miss parts

5. But it’s very fast and real-time

Or like live streaming:

1. If a frame drops, the stream keeps going

2. It doesn’t stop to fix old data

3. Speed is more important than perfection

So UDP = Fast, real-time, but risky

Used for: online games, video calls, live streaming, voice chat, etc.

TCP VS UDP

What is HTTP and where it fits

HTTP (HyperText Transfer Protocol) is called an application-level protocol because it defines how applications communicate, not how data is physically transported over the network.

The application layer is the top layer where user applications work, like:

1. Web browsers (Chrome, Firefox)

2. Mobile apps

3. Web servers

4. APIs

HTTP works here and decides:

1. How a request should look (GET, POST, headers, body, etc.)

2. How a response should look (status code, headers, data)

3. How resources like web pages, images, JSON, etc. are requested and sent

Why HTTP is NOT a Transport Protocol?

Transport protocols (like TCP and UDP) are responsible for:

1. Breaking data into packets

2. Sending data reliably or fast

3. Handling errors, retransmission, ordering

4. Managing connections

HTTP does not do these things.

1. HTTP uses TCP (or sometimes UDP via QUIC in HTTP/3)

2. HTTP assumes data will be delivered by the transport layer

3. HTTP only cares about what data is sent and in what format

TCP = How data moves

HTTP = What data means and how apps talk

Clarifying the Layering : HTTP Runs on Top of TCP

In computer networks, communication is organized into layers, where each layer has a specific job.

1. HTTP is an application-layer protocol.

2. TCP is a transport-layer protocol.

This means HTTP depends on TCP to send and receive data.

How they work together

1. Your browser creates an HTTP request (e.g., GET /index.html).

2. HTTP formats this request (methods, headers, body, etc.).

3. This HTTP message is then handed to TCP.

4. TCP takes care of:

   a. Splitting data into packets

   b. Reliable delivery

   c. Ordering packets

   d. Retransmission if packets are lost

5. The server receives the data via TCP and passes it up to HTTP, which interprets the request and sends back an HTTP response the same way.

So the flow is:

1. Application Layer: HTTP (what to say, format of message)

2. Transport Layer: TCP (how to send it reliably)

3. Internet Layer: IP

4. Link Layer: Ethernet / Wi-Fi