3D Network Simulator

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🌐 TCP (Transmission Control Protocol)

📞 Think: Phone Call — you talk only after both sides agree to connect.

🔹 Step 1 (Before TCP): DNS Query

Before the "phone call" (TCP) can start, your computer needs to find the server's "phone number" (IP Address).

• Client (Your system) → "Hey DNS Server, do you know the IP of www.youtube.com?"
• DNS Server → "Yes, its IP address is 142.250.190.206."

👉 Now your system knows the exact address of the server it needs to contact.

🔹 Example: Opening a Website (like https://google.com)

Step-by-Step (The 3-Way Handshake):

• You (Client) → "Hey Server, are you there?"
  → This is a SYN packet (synchronize).
• Server → "Yes, I’m here! Ready to talk!"
  → This is a SYN-ACK packet (synchronize-acknowledge).
• You (Client) → "Great! Let’s start sending data."
  → This is an ACK packet (acknowledge).

✅ This 3-step process is called the 3-Way Handshake.

Data Transfer:

Now you send an HTTP request (“Give me google.com’s homepage”). The server sends back the HTML page. Every packet sent has an ACK confirming it was received. If a packet is lost, TCP retransmits it. When the job is done, the connection is closed gracefully.

🧠 Real-Life Analogy

Action	Real Example	TCP Concept
“Hello, can you hear me?”	You start a call	SYN
“Yes, I can hear you!”	Other person replies	SYN-ACK
“Okay, let’s talk”	You confirm	ACK
Talk continues clearly	Data exchange	Reliable transmission

⚙️ Common Ports using TCP

• HTTP: Port 80
• HTTPS: Port 443 (Used in this simulation)
• FTP: Port 21
• SMTP (Email): Port 25

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🌐 UDP (User Datagram Protocol)

📬 Think: Sending a Postcard — you just drop it in the mail, no guarantee it arrives.

🔹 Example: Watching a Live Stream or Online Game

When you stream a live cricket match 🎥:

• The video packets are sent continuously using UDP.
• If a small packet (a single frame) is lost, the video still plays. You don’t want the entire stream to pause and wait for that one missing piece.

This simulation demonstrates two states based on your selected bandwidth:

• Play Phase: When UDP packets are flowing smoothly (bandwidth >= 10 MBPS).
• Buffering Phase: When UDP packets are delayed or bandwidth is low (< 10 MBPS), the stream pauses to "buffer" (catch up).

Step-by-Step Flow:

1. You (Client) open Hotstar
   → Your device sends a DNS Query: “Hey DNS, what’s the IP of hotstar.com?”
2. DNS uses UDP (Port 53)
   → Fast, no connection setup. If a packet is lost, it just sends again — no waiting for acknowledgment.
3. DNS Replies
   → “The IP of hotstar.com is 142.250.183.238”. Still using UDP. DNS is done! ✅
4. You connect to Hotstar’s Streaming Server
   → Data transfer now uses UDP (e.g., Port 1935). This could be RTP or QUIC for live video.
5. Live Stream Begins
   → Hotstar’s server keeps sending video packets continuously. No handshake, no acknowledgment.
6. Goal = Speed > Accuracy
   → Even if some packets are lost, the video still plays (maybe a tiny blur), but the stream continues.

🧠 Real-Life Analogy

Action	Real Example	UDP Concept
You send a letter to 10 friends	You don’t wait for replies	Connectionless
If one letter is lost	You don’t resend it	Unreliable
Messages go quickly	Fast communication	Low latency

🧩 Final Comparison Example

Feature	TCP (Web Page)	UDP (Video/Game)
Type	Connection-oriented	Connectionless
Example	Opening google.com	Watching YouTube Live
Packet Loss	Retransmitted	Ignored
Reliability	High	Low
Speed	Slower	Faster
Use Case	When accuracy is important	When speed is important

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Where do they fit in the OSI Model?

Both TCP and UDP operate at Layer 4 — The Transport Layer of the OSI model.

This layer is the "Traffic Controller" of the network. It's responsible for end-to-end communication, breaking data into segments, and deciding how that data travels.

Protocol	OSI Layer	Function
TCP	Layer 4 – Transport	Reliable delivery, acknowledgment, error checking, retransmission.
UDP	Layer 4 – Transport	Fast, connectionless, no acknowledgment, no retransmission.

How They Work with Other Layers (Example):

When you open YouTube (TCP):

• Layer 7 (Application): Your browser uses HTTP/HTTPS.
• Layer 4 (Transport): TCP ensures the website data (HTML, images) arrives reliably.
• Layer 3 (Network): IP routes your request to YouTube's server.

When you watch a Live Stream (UDP):

• Layer 7 (Application): The streaming app (e.g., Hotstar).
• Layer 4 (Transport): UDP sends the video packets fast to keep it "live".
• Layer 3 (Network): IP routes the video data from the server to you.