1. Introduction: Why the Internet Needs Rules

• How data travels and why protocols exist

2. What Are TCP and UDP?

• TCP = reliable

• UDP = fast

3. TCP Explained (Safe and Reliable)

• How it ensures delivery

• Analogy: phone call / courier

4. UDP Explained (Fast but Risky)

• How it priorities speed

• Analogy: live broadcast / announcement

5. Key Differences Between TCP and UDP

• Speed vs reliability

• Connection vs no connection

• Simple comparison

6. When to Use TCP vs UDP

• Practical use cases for both

• Real-world examples

7. What Is HTTP and Where It Fits

• Application-layer protocol

• Not responsible for delivery

8. TCP vs HTTP: Clearing the Confusion

• HTTP runs on TCP

• Why HTTP ≠ TCP

9. Conclusion:

• Choosing the Right Tool

1 . Introduction

Have you ever thought that whenever we send some data over the internet how it gets delivered to the exact location , how our ISP knows that when to transfer the data safe and fast . This all is possible because of the internet protocols and rules which manages billions of devices across the global network . This protocol serves as a common language for the computer to understand how to format , address , route and reassemble the data .

This protocols are essential for ensuring the compatibility , Reliability of data delivery , Error Connection and managing traffic . Without this rules and protocols it would have become a headache to transfer data as the data can get lost or unreadable as it travel across the devices and there would be no safe way to verify that if the data has arrived safely or not making the modern web browsing , streaming and gaming impossible .

In this blog we are going to explore about the rules and protocols which govern the internet and we are also going to see that what is the use case of different protocols like TCP and UDP and how the HTTP request flows over the TCP connection and when to use TCP protocol and when to use UDP protocol .

2 . What are TCP and UDP

TCP ( Transmission Control Protocol ) and UDP ( User Datagram Protocol ) are core transport layer protocol OSI and TCP/IP models . Both are responsible for end - to -end communication between the application but they both differ significantly in the terms of reliability , speed and use case . Understanding the difference between the TCP and UDP is essential for designing the efficient and reliable system . Lets understand the TCP and UDP in detail

TCP (Transmission Control Protocol )

The TCP is more reliable and connection oriented transport protocols , It established the connection using three - way handshake and guarantees that all packet arrives correctly .

1. Use a three - way handshake to establish the connection .

2. Breaks data into packet and reassemble into same order.

3. Retransmit lost or corrupted packet automatically .

4. Provides reliable , error - checked communication.

5. TCP is mostly used for Web Browsing , Email , File transfer , Remote Access, Online banking and financial transactions .

UDP ( User Datagram Protocol )

The UDP is lightweight connectionless protocol prioritising speed over reliability which is more suitable for real time applications , The UDP does not follow any three -way handshake due to which there can be loss of data packets and shift in the order of the data .

1. UDP is not that much reliable as compared to the TCP .

2. The UDP protocol has the fastest speed .

3. The order of the data is undefined .

4. UDP is mostly used at places where losing packet better then the high latency like gaming , DNS , Voice over IP and Live video Streaming .

3 . TCP explained in brief

As we know that TCP stands for transmission controlled protocol and it is connection based transport protocol which uses Three - way handshake which makes it more reliable for data transfer and communication . In TCP the order of the data is same and if the packet is lost then it will retransmit which make it slower but dependable , TCP controls the flow of data to prevent the overwhelming to the receiver .

• TCP uses three way handshake to stablished the connection , the three - way -connection works on the basic of the SYN, SYN-ACK, ACK which ensures that the both the sides client and server are synchronised and ready to share the data . The handshake looks something like this :-

• The header of the TCP can range from 20 - 60 bytes . 40 bytes are for options. If there are no options , a header is of 20 byte else it can be most of 60 bytes .The header field contains the data like this :-

• Source port / Destination port : This is of 16 bits each which identifies the sending and receiving of the application .

• Sequence Number : This is of 32 bits in which the position of the first byte is used for ordering . i.e to maintain the ordering number .

• Acknowledgment Number : This is also of the 32 bits and the next byte is expected by the receiver .

• Header Length : This contains around ( 5- 15 ) words i.e is around 20 - 30 byte .

• Control Flags ( 1 bit each ) :

1. URG : Urgent .

2. ACK : Acknowledgment .

3. PSH : Push data immediately.

4. RST : Reset connection .

5. SYN : Synchronise sequence numbers.

6. FIN : Terminate the connection .

• Window Size : Receiver buffer size for control flow .

• CheckSum : Error detection mandatory.

• Urgent Pointer : This is the position for urgent data .

Understanding the three-way handshake of the TCP

Communication over the internet follows the TCP/IP model .Applications like web breakers uses the application layer and then their data is passed to the transport layer .

TCP ensures the reliability using the Positive Acknowledgment with the Retransmission . It synchronises sequence numbers, exchanges window sizes, and verifies both parties are ready to communicate, ensuring reliable, ordered data delivery.

The three - way handshake Process looks something like this :-

1. SYN ( Synchronise ) : The client initiates the connection by sending a TCP Segment with the SYN flag which is set to 1 to the server , along with a random initial sequence number ( ISN ) for eg - x .

2. SYN - ACK (Synchronise - Acknowledgment) : The server server receives the SYN , and it sets the SYN and ACK flag to 1 and then it responses with its own random sequence number ( eg - y ) then the Acknowledgment number is set to the clients ISN + 1 i.e ( x + 1 ) .

3. ACK Acknowledgment : The client acknowledges the server's response by sending an ACK segment with the ACK flag set to 1 . The sequence number is x + 1 and the acknowledgment number is y + 1 and once the server receives this the connection established successfully .

Lets understand this with the help of Phone call analysis :-

Before the data is send the TCP established the connection ensuring that the dat is shared without any problem : -

1. SYC (Synchronise ) : Lets say that you have called your friend the first thing which you say is hey can you hear my voice ?

2. SYC - ACK ( Synchronise - Acknowledge ) : Now your friend answer the call Yes I can hear you voice , can you hear my voice and I'm ready to listen .

3. ACK ( Acknowledgment ) : Now you can easily start to share the store with your friend because the three - way handshake is done .

Now lets understand how the Reliable data - delivery works with the analogy of the courier

Once the connection is established and data is shared the TCP breaks the larger files into smaller pieces called segments. Lets imagine that we are sending a 1000 page book , the TCP will not throw the book in the air it will delivery it with the help of courier service i.e every pages will align with the exact index order .

• Sequence Number : Every single segment gets number ( just like the page number of the book ) . If segment 4 arrives earlier then segment 3 then the receiver knows that segment it has to wait for the segment 3 before showing the content .

• Acknowledgment ( Signed Receipt ) : For every packet received the courier ( TCP ) sends a signed receipt back to the sender .

• Retransmission ( Lost Parcel Protection ) : If the sender doesn't receive the " signed receipt " for certain package within a time period , they assume that it has been lost and then it will automatically resend that package again .

Connection termination :

When the conversation is over the TCP closes the connection by ensuring that no data is left in between .

• FIN (Finish): I'm done sending the data.

• ACK (Acknowledgment): Okay, I received your request to stop .

• FIN: Okay, I'm done too.

• ACK: Bye Bye ta ta !!!

4 . UDP explained in brief :

User Datagram Protocol is a Transport layer protocol of the IP which provides fast , connectionless and lightweight connection between the process . The UDP does not guarantee delivery packages in order and no error connection, the UDP throw the data as fast as possible making it ideal for the real time applications like video streaming , gaming , live show etc .

UDP is faster but less reliable as we compared to the TCP as UDP accomplishes this process in a simple fashion : It sends packets ( unit of data transmission) directly to the target computer without establishing the connection first, indicating the order of set package or without checking which package has arrived first .

Now lets understand the key aspect of the UDP : -

• Connectionless : Unlike the TCP the UDP does not need any three-way handshake which makes the data transfer very fast as compared to the TCP .

• Unreliability : The UDP does not use any signed receipts for the acknowledgment which means that data can be lost , duplicated or can be sent out of order .

• Light-weight Header : The UDP uses a small weight header of around 8 bytes i.e Source Port , Destination Port , Length and checksum .

• Best - Effort Delivery : It relies on the IP to send the packets without tracking it .

Application of UDP :

UDP are preferred where low latency is crucial and occasional packet lost is acceptable .

1. DNS uses UDP for query / response lookups since the domain name queries are small and need instant response .

2. DHCP uses UDP for dynamically assigning the IP address of any device, and very small controls message is exchanged .

3. VoIP uses the UDP for real -time voice communication as it can tolerate some packet loss but not delays .

4. RIP uses UDP to send a periodic routing update between the router efficiently.

5. NTP uses UDP to synchronise the system clock across the network with minimal delay .

Use of UDP in DDOS attack :

A UDP flood attack is a type of Distributed Denial of Service attack where the hacker sends a larger number of UDP packets to target port exploiting UDP's connectionless nature .

The Attack process looks something like this : -

• The attacker sends a massive UDP packets with spoofed IP addresses to random port on the target .

• The target checks for the active application on that port .

• It response with an ICMP "Destination unreachable " messages , overloading its own resources .

Mitigation :

• It helps to monitor for abnormal UDP traffic spikes .

• Uses rate limiting , firewalls and intrusion prevention systems .

• Deploy DDOS prevention service for large scale attacks .

UDP communication do not go through any kind of process , Instead , one computer can simply begin sending data to other .

5 . Key difference between TCP and UDP

The difference between the TCP and UDP is given below :

6 . When to use TCP and UDP

The key aspect to use TCP and UDP are given below : -

Some applications like Zoom , google meet Skype uses both TCP and UDP protocol for connection , video and audio is shared over UDP and the chat ,login and files are shared over TCP even the games uses UDP for player moment actions and other thing and TCP is for login , matchmaking and purchase .

7 . What is HTTP and where does it fits

Hyper Text Transfer protocol is the foundational protocol used by the World Wide Web to structure the request and response enabling the communication between the web browser and web server . It is the set of rules which determines how hypermedia documents such as HTML are transferred .

• Request - Response Mechanism : HTTP operates on a client - server model . A user agent i.e browser sends request to the server and the server returns the response .

• Stateless Protocol : Each HTTP request is processed independently; the server does not retain the data between the request unless it is authorized by mechanisms like cookies.

• Text - Based : Messages are plan text for human readability , making them easy to debug .

• Extensible : Through headers , clients and server can exchange extra information to negotiate content, manage sessions, or enforce security

• Secure vs. Unsecure: HTTP typically uses port 80. Its secure counterpart, HTTPS, uses TLS/SSL encryption and typically operates on port 443

Where does the HTTP fits in the application layer

In the OSI model ( Open system Interconnection model ) the HTTP operates at the layer 7 which is the application layer .

• Topmost layer : At the highest level it is closest to the user and directly with software applications ( web browser , email clients ) .

• Focus on Data Definition : The Application layer is responsible for the protocols and data manipulation on which the software depends to share the data with the user .It defines how the request is formatted ( i.e GET /index.html HTTP/1.1)

• Interface to lower layers : While the HTTP handle "What " i.e requesting a file and it relies on the lower layers for the "How" ("delivering the packets), typically using the TCP (Transport Layer 4) or QUIC/UDP (HTTP/3).

Key Components of the HTTP

• HTTP methods : This helps to define which actions should be taken such as GET , POST , PUT , DELETE .

• Status Code : This are the numbers which indicates the success or failure of the request .

• Headers : Metadata that provides information about the request or response such as cashing info , content type and cookies .

Not responsible for delivery

HTTP is not responsible for the delivery of the data because it operates at the Application layer i.e is layer 7 of the OSI model and the and the Data is delivered at the transport layer .

8 . TCP v/s HTTP

TCP is a transport layer protocol providing reliability , order of data where as HTTP is an application - layer protocol running over TCP that defines how browser and servers format , request and transfer web content

lets understand the difference in breif :

9 . Conclusion :

In this blog we have explored mainly two types of transport protocols i.e TCP and UDP , we also got to know that which protocol is suitable for which use case and why TCP is more reliable as compared to the UDP and how UDP is more faster then the TCP . If we also seen the different use case of the protocols and how many applications uses both the protocols to establish the connection .

We have also explored the HTTP protocol which is an application layer protocol and how it is different from TCP and how HTTP controls what data is to be shared.

If you stayed till last thank you for your patience and thank you for reading out my blog . If you like the blog please try to share it with your friends and family members and also feel free to share your feedback . pls like and share the blog .

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