TCP/IP Basics: The Language of the Internet

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Summary
Learn the fundamentals of the TCP/IP protocol suite, including handshakes, packet segments, and how it powers connectivity in Bangladesh.

TCP/IP Basics: The Language of the Internet

Summary

TCP/IP (Transmission Control Protocol/Internet Protocol) is the suite of protocols that actually runs the internet. While the OSI model is for teaching, TCP/IP is the “working” model used by every computer, smartphone, and router in Bangladesh to exchange data.

Overview

TCP/IP is designed to be decentralized and resilient. If one part of the network goes down (like a cut submarine cable), the protocol suite is built to find another path for your data. It consists of two main parts:

  • IP (Internet Protocol): Responsible for addressing and routing packets to the right destination.
  • TCP (Transmission Control Protocol): Responsible for ensuring those packets arrive in the correct order and without errors.

Technical Deep-Dive

The 3-Way Handshake

Before TCP sends any data, it performs a “Handshake” to make sure the receiver is ready:

  1. SYN: Client says “I want to connect.”
  2. SYN-ACK: Server says “I heard you, I’m ready.”
  3. ACK: Client says “Great, let’s start.”

Packet Segments

Data is broken into small pieces called packets or segments. Each packet has a header containing the source IP, destination IP, and a sequence number. If packet #3 is lost, TCP detects the gap and asks the server to send it again.

Bangladesh Context

The efficiency of the TCP/IP handshake is highly dependent on Latency:

  1. BDIX Advantage: On a local BDIX connection, the 3-way handshake takes less than 10ms. This makes websites feel “snappy” and instant.
  2. Submarine Cable Impact: When connecting to a server in the USA, the handshake must travel across the ocean three times. This can take 600ms or more just to start the connection, which is why international sites feel slower to load initially.
  3. MTU Issues: Many ISPs in Bangladesh use PPPoE over fiber. This requires a slightly smaller “packet size” (MTU of 1492 instead of 1500). If this is not set correctly on your router, some websites may fail to load even though your internet is “connected.”

Troubleshooting

  • Website “Timed Out”: This usually means the 3-way handshake failed because the server didn’t respond or the path was blocked.
  • Slow Initial Loading: High latency on the first few packets is often a sign of a congested ISP gateway.

FAQ

What is the difference between a packet and a segment?

A “Segment” is the unit of data at the Transport Layer (TCP). Once it gets an IP address and moves to the Network Layer, it is called a “Packet.”

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References