DEV Community: arshad. dev

TCP: Handshake to reliability

arshad. dev — Mon, 22 Jun 2026 01:22:34 +0000

Introduction

Imagine two people are on a phone call , without saying "hello" to each other , And without confirmation what they heard think about it messages can get overlap or lost and can be miss understood

Computer networks faces the same problem, just take an example theres a two devices and one device just threwing the data to another one wihtout any rules, so communication would become messy, unstructured & also unreliable.

And this is where (TCP)Transmission Control Protocol comes into the picture , its make sure the data which is traveliing has discipline , proper structure in ordering wihtout curroption
it takes the responsibilities and confirmation to network communictaion so data arrives safely

What is TCP and Why It Is Needed?

TCP(transmision control protocol) is a foundtaional internet protocol that ensures devices can communicate reliably over a network. It cuts data into small packets, track them with sequence numvber and verifies their delivery so that nothing is lost or corrupted or missed a data packet

TCP is just working internally to make sure :

No a single data packet is lost
data arrives in correct order sequence
Guaranteed delivery
flow & congestion control

what would happen wihtout tcp mordern internet services like web browsing ,emails, and file transfers would completely fail . Because TCP guarantees data arrives in a order and wihtout loosing it .

What problem TCP is designed to solve?

the (TCP) was desinged to solve the problem of unreliable data communication across computer network , it provides a reliable , ordered , and error checked delivery.

Core problems TCP solves

data loss & Corruption (IP network can drop, dupicate or corrupt packets.)
Out of order delivery (each packet and reassemble them in the exact order they were sent.)
Network Overload Congestion (sending data too fats can overwhelm routers and cause packet loss.)
Recivers Overwhlem flow control (A fast sender can easily Overwhelm a slow recivers processing capabilities or memory buffers.)

What is the tcp 3 way handshake

it gaurantees both devices are ready to communicate and sets the stage for error-free data exchange , TCP makes connection between a client and a server before any acutal data is transferred,

think of it like starting a conversation

Can we talk?
Yes, we can talk
Great, lets start

This setup process is called the 3-way handshake. It makes sure both sides are ready and agree on some initial numbers used to track data.

Step-by-Step Working of SYN, SYN-ACK, and ACK

Lets understand this through a Phone call example

SYN(Synchronize) : you call a freind and say, "hello", can you here me?

2.SYN-ACK (Synchronize + Acknowledge) : your freind answers , "yes", I can hear you clearly! Can you here me ?

3.ACK(Acknowledge) : you reply,"yes, I can hear you too!"

After this, both sides trust each other and know where to start counting data from.

How Data Transfer Works in TCP

Data transfer in TCP works by breaking messages into manageble chunks called segments , and using a system of ACK to guarantee nothing is lost or out of order

Example:

Chunk 1 -> number 1
Chunk 2 -> number 2
Chunk 3 -> number 3

The entire process occurs in three main stages:

Connection Eshtablishment (three-way HandShake)
The data transfer Phase
Reliability & Flow control.

How TCP handles packet loss?

TCP handles packet loss by detecting gaps in data delivery, resending the missing packets, and slowing down transmission speeds to ease network congetsion,Because TCP guarantees that every single byte arrives perfectly , it use 3 main ways to spot and fix a lost packet.

Fast Retransmit(The Quick Fix)

2.Retransmition TimeOut (the backup plan)

Adjusting Speed(congestion control)

This is how TCP avoids gaps in the final data.

CONCLUSION

TCP turns messy internet traffic into a reliable data strem , by tracking every piece, resending lost data, and slowing down when networks get crowded it make sures nothing get corrupted.

linux commands

arshad. dev — Sun, 21 Jun 2026 02:16:51 +0000

what are commands

linux commands are text instructions used to interact with operating system through termilnal

help beginners understand and use linux terminal effectively
useful for students , developers, and system administrators

All about DNS (domain name system)

arshad. dev — Sun, 21 Jun 2026 01:56:11 +0000

DNS resolution
imagine you are chilling and you opened browser and entered www.youtube.com
in your browser , the system does not understand the name directly
it translates it into ip adress of the server hoisting the website

this allows browsewr connect to correct server

How does it actually works ?

WORKING : term(DNS) brokes into multiple steps , so user can access simply entering website name into their browser

*what happens internally *
when user enters www.youtube.com in their browser:

root server
root server gives information who saves www.youtube.com
next it refers to (TLD) information

TLD

what is (TLD) Top level domain
the TLD server directs the resolver to the domains Authoritative server.

Authoritative server response

the Authoritative server returns the actual IP address.

Final response

the resolver sends the IP back to the user , and the browser connects to the server

and all these happens in under milli seconds

An article about hardware router , modem , switch , firewall , hub & loadBalancer.

arshad. dev — Sun, 21 Jun 2026 01:20:22 +0000

Router
A router is a networking device that connects multiple computers and devices to each other and to the internet

Example: when you access any web , request is broken into multiple parts in the form of packets , these packets dont travel directly to web
there is a series of routers that checks and send them forward until they reach their correct destination

Modem
A modem is a hardware device that connects your home or office network to your internetServiceProvider(ISP)

modem allows to connect only specific numbers of devices to the internet.

Diffrence between Modem VS router

in simple words ,
modem connects your home to the internet.
router connects your devices to each other , creating a local area network(LAN)

Switch

switch is a hardware device that connects multiple wired devices such as (computers , printers , and servers ) together in a single LAN(local area network)

its responsible for filtering and forwarding the packets between local area network segments based on MAC address

it transfers the data only to the device that has been addressed,

Firewall

a firewall is a network security system , available as a hardware and software that checks incoming and outgoing trafic based on protocols.

in simple words : its like a security gaurd which filters the data packets
if it accepts then allows the traffic , or reject them with an error response either block silently without response

firewall is a barrier between (LAN) & (WAN)

conclusion: all the packets incoming or outgoing in network it should pass through the firewall

LoadBalancer

a loadbalancer behave like a traffic director for computer servers it sits between user and backend servers

in simple words : a traffic cop routing client requests across all servers.

benifits

ensures server do not become overwhelmed
prevent crashes .
speed up response at time.
ensures high availability.