Imagine this: You are in a classroom and you want to ask your friend to give you a pencil. He is sitting far from you. The classroom is full of noise and disturbance. You shout at your friend saying “Hey John, give me a pencil”. But what he did was gave you an “pen”. That means in the room full of noise and disturbance your friend could not hear you properly.
Same things happens in the internet as well. There are a lot of traffic and noise while transmitting data from one computer to another. So what they decided that they will have a set of Rules that the Sender and the Receiver should follow in order to transmit data safely and securely.
There are a lot of rule to communicate but in this blog we will generally discuss about Transmission Control Protocol(TCP) and User Datagram Protocol(UDP).
Protocol is a set of rules and guidelines that govern the communication and interaction between different entities in a system. In the context of computer networks, a protocol defines how data is transmitted, received, and interpreted between devices or systems to enable effective communication.
Transmission Control Protocol
TCP (Transmission Control Protocol) is a protocol that allows devices to communicate reliably over a network. It ensures that data reaches the destination correctly and in the right order, even if parts of the network are slow or unreliable.
It uses 3-way Handshake to establish the connection and uses 4-way handshake to terminate the connection.
Characteristics of TCP:
- Reliability - Even if the network is slow, it will ensure that the data reaches its destination.
- Ordering - The sequence of the data packet from the sender must be the same as that of the receiver.
- Loss Detection - It has the capability to detect the loss of a packet during transmission.
- Retransmission - After detecting the loss of a packet, It can initiate a retransmission.
- Flow Control - The rate at which the data is sent from the sender must be the same as the data is received by the receiver.
- Congestion Control - It reliably controls the traffic in the bandwidth.
TCP is like sending a package through a reliable courier service. The courier confirms delivery, checks that nothing was damaged, and ensures everything arrives in the right order. If something goes wrong, they resend it.
Real-World use case:
- Text messaging
- File download
- Web Browsing
- Database transaction
User Datagram Protocol
UDP(User Datagram Protocol) is a protocol that sends data packets without establishing a proper connection. It is fast compared to TCP but less reliable. Data packets may or may not received correctly or in correct order. There can be a change of packet loss.
Characteristics of UDP:
- Connectionless: No handshake is needed before sending data, reducing delay.
- Less-reliable: Doesn't guarantee packets arrive, arrive in order, or arrive without duplicates.
- Fast & Lightweight: Minimal overhead and processing, making it quick
UDP is like making an announcement over a loudspeaker. You broadcast your message quickly, but you don't wait for confirmation that anyone heard it, and you don't check if they got every word. It's fast, but there's no guarantee.
Real-world use case:
- Video calls
- Video live streaming
- Multi player Games(Valorant, Pubg)
- IoT sensor updates
Difference between TCP and UDP
| TCP | UDP |
|---|---|
| Secure | Unsecure |
| Connection-Oriented | Connection less |
| Slow | Fast |
| Guaranteed Transmission | No Guarantee |
| Flow control | No flow control |
| Error Control | No error control |
Hypertext Transfer protocol
HTTP (Hyper text transfer protocol) is a type of protocol that defines what is the data and how the applications should communicate. HTTP is an application layer protocol designed to transfer information between networked devices and runs on top of Transmission Control Protocol.
You went to a restaurant and the waiter comes to your table and ask “Can I take your order?”. You said “Yes!”. The waiter the confirms “Yes, I am listening.” The connection is now established. This is what TCP does.
HTTP is what you actually say to order. Example: “Get me 1 Chicken Pizza. No Cola. Just bring water”. HTTP defines what the request is like. The response can be: “Order accepted”, “Item is not available” or “Order complete”. HTTP will not ensure delivery.
Flow of data transmission using HTTP and TCP
- TCP sets up the connection
- HTTP sends the request
- TCP ensure it reaches correctly
- HTTP sends the response
- TCP ensure that the message delivered correctly.
Why HTTP Does Not Replace TCP
This is a common beginner confusion: "If I'm using HTTP, do I still need TCP?"
Yes! They work together but serve different purposes:
TCP handles the reliable transport of data
HTTP defines the structure and meaning of web communication
Without TCP underneath, HTTP would have no reliable way to deliver its messages. You could theoretically run HTTP over UDP (and some experimental protocols do this), but standard HTTP/HTTPS uses TCP because web content needs to arrive completely and correctly.
Conclusion
Understanding the internet is like understanding a well-organized delivery system. At its core, the internet needs rules to function, and that's exactly what protocols provide.
TCP and UDP are the delivery mechanisms. TCP is your reliable postal service, slower but guaranteed to get your package there intact and in order. UDP is your live broadcast—fast and efficient, but some messages might get lost along the way. Neither is better than the other; they're simply tools for different jobs. Use TCP when you can't afford to lose data, and use UDP when speed matters more than perfection.
HTTP is the language of the web. It's not a replacement for TCP or UDP rather it's a layer that work on top, defining what web browsers and servers say to each other. When you load a website, HTTP formats your request ("Give me this page"), while TCP ensures that request actually arrives safely.
Together, they power your internet experience. Every time you browse the web, stream a video, play an online game, or send an email, these protocols are working behind the scenes. TCP and UDP handle the transportation, HTTP handles the conversation, and the internet just works.
The beauty of this system is its simplicity: each protocol does one job well, and by working together in layers, they create the connected world we use every day. You don't need to memorize every technical detail—just remember that reliable communication needs TCP, fast communication can use UDP, and web communication speaks HTTP on top of TCP.
Now you know the foundation of how the internet talks to itself. The next time you click a link, join a video call, or send a message, you'll understand the invisible protocols making it all possible.
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