Day 14b –TCP and UDP

This is Part 2 of the Networking for DevOps series.

In the previous part, we understood https://90-days-devops-with-shubham.hashnode.dev/day-14a-networking-fundamentals

Now, let’s see how data is actually delivered using TCP and UDP.

What is TCP?

TCP (Transmission Control Protocol)

TCP is basically the “reliable delivery system” of the internet.

Let’s make it simple

Think of TCP like a Courier with tracking

When you send something (message, file, request), TCP makes sure:

✔ It reaches the destination
✔ It arrives in correct order
✔ Nothing is missing
✔ If something is lost → it is re-sent

TCP Internal Flow

1. Prepares delivery with tracking

2. Adds sequence numbers

3. Travels across network

4. Receiver rebuilds message

5. Missing parts are resent

6. Final message is correct

Example:

You send:

“Order pizza at 8 PM”

TCP does this behind the scenes

1. It prepares delivery with tracking system

TCP says:

• “I will deliver this message safely”

• “I will track everything properly”

2. It adds hidden order numbers (not visible to you)

Instead of breaking it like physical pieces, TCP:

• tags data with sequence numbers

• so receiver knows the exact order

Think:

like numbered pages in a notebook

3. Message travels through internet

• Data moves across routers

• May take different paths

• Still tracked in background

4. Receiver rebuilds message

Receiver gets data like:

• “Order”

• “pizza”

• “at”

• “8 PM”

Even if it arrives mixed up, TCP:

• rearranges using sequence numbers ✔

So final message becomes:

“Order pizza at 8 PM”

5. If something is missing

If “8 PM” part is missing:

• receiver says: “send that part again”

• sender resends ONLY missing part

6. ✔ Final result

Message is complete, correct, and in order.

TCP = Reliable system

Send message → Label data → Transmit → Rearrange 
→ Fix missing → Deliver correct message

TCP = “Even if data arrives messy, system fixes it and guarantees correct message”

TCP = “Safe delivery mode”

You → Internet → Friend

✔ No loss  
✔ No corruption  
✔ Correct order  
✔ Guaranteed delivery

Real-world analogy (TCP)

TCP used in real world

✔ WhatsApp messages

✔ SSH (port 22)

✔ HTTPS websites (port 443)

✔ curl requests

✔ File downloads

What is UDP?

UDP is the “fast but no guarantee system”

Think of it like a Live Cricket Score update system

UDP (User Datagram Protocol)

👉 UDP = “send and forget”

You:

• Send data

• Don’t wait

• Don’t confirm

• Don’t resend

Live Cricket Score example (UDP)

Imagine watching IPL score:

• 6 runs update → shown instantly

• Next ball update → comes next

• If one update is missed → NO problem

👉 You don’t care about old missing updates

👉 You only care about latest score

That’s UDP

UDP flow (simple)

Server → sends updates → You watch

✔ Fast  
❌ No guarantee all packets arrive  
❌ No retry  
❌ No order guarantee needed

Real-world analogy (UDP)

Why UDP is used

Because:

SPEED > PERFECT DELIVERY

Even if something is missing → system continues

TCP vs UDP (super simple)

• TCP = Courier (safe, tracked, confirmed)

• UDP = Live cricket score (fast, no guarantee)

TCP → “Make sure it arrives correctly” 
UDP → “Send fast updates, don’t worry if something drops” 

Next: https://90-days-devops-with-shubham.hashnode.dev/day-14c-where-http-tcp-ip-actually-sit-layer-mapping-simplified

#90DaysOfDevOps #DevOpsKaJosh #TrainWithShubham