What Is a Packet? — Solitary Func

Before we can trace a UPI payment or understand how a tracker follows you across the web, we need to understand the smallest unit of the internet: the packet.

The Dabbawala Metaphor

In Mumbai, dabbawalas deliver over 200,000 lunchboxes every day. Each dabbawala doesn’t carry a full meal across the city — the system works because lunchboxes are handed off between carriers at transit points, each person responsible for only their leg of the journey.

The internet works the same way.

When you send a message to someone, your phone doesn’t open a direct wire to their phone. Instead, your message is broken into small chunks — packets — and each packet finds its own way through the network, handed off between routers like a lunchbox between dabbawalas.

Anatomy of a Packet

Every packet has two parts:

The header — the label on the lunchbox. It contains:

Source address: where this packet came from (your device’s IP)
Destination address: where it’s going (the server’s IP)
Sequence number: which piece of the original message this is (so the receiver can reassemble them in order)
Protocol: the rules this packet follows (TCP for reliable delivery, UDP for speed)
TTL (Time to Live): how many hops this packet can make before it’s discarded — a safety mechanism to prevent lost packets from circling forever

The payload — the actual content. A fragment of your message, a piece of an image, a slice of video. On its own, often meaningless — but combined with the other packets, it reconstructs the full data.

Why Packets, Not Streams?

The early telephone network used circuit switching — when you called someone, a dedicated wire was held open for the entire conversation. This worked for voice, but it was wasteful. Most of the time during a call, you’re not actually talking. The wire sits idle.

Packet switching solved this. By breaking data into packets, many conversations can share the same wires simultaneously. Packets from different senders interleave on the same cable, each finding its way to the right destination. It’s the difference between reserving an entire highway lane for one car versus letting all cars merge onto a shared road.

This is why the internet is efficient. This is also why it’s complex — packets can arrive out of order, get lost, or take different routes. Protocols like TCP exist to handle this chaos, requesting retransmission of lost packets and reordering what arrives.

Packets in the Wild

Every digital action you take produces packets:

Opening Instagram: your phone sends packets requesting the feed. The server responds with hundreds of packets carrying image data, text, metadata. Your phone reassembles them into the experience you see.
A UPI payment: your BHIM app sends a small cluster of packets to the NPCI switch, which routes them to the recipient’s bank. The entire transaction might be 20-30 packets, but each one passes through multiple intermediaries.
An online game: hundreds of packets per second fly between your device and the game server, carrying your inputs and receiving world state updates. If a packet is lost, your character stutters. If it arrives late, you experience lag.

What Packets Reveal

Here’s the thing about packets that matters for DataFolks: even when the payload is encrypted (and it usually is, thanks to HTTPS), the header is visible. Anyone between you and the destination — your ISP, your office network, a government monitoring system — can see:

That you connected to a specific IP address
When you connected and for how long
How much data you exchanged
The pattern of your connections over time

This is metadata, and it’s often more revealing than the content itself. We don’t need to read your messages to know that you called a divorce lawyer at 2 AM, then a real estate agent the next morning.

Packets are neutral. They’re just containers. But the systems that route, inspect, and log them are not.

This is Chapter 1 of DataFolks. Next: How UPI Actually Works — tracing a single payment through India’s digital infrastructure.