What Is a Packet? — Solitary Func

You open YouTube. You tap a video. Within a second, the first frame appears and the audio starts. It feels instant, like the video was always there, waiting inside your phone.

It wasn’t. In that one second, your phone reached out across the internet to a server that might be sitting in a data center in Mumbai, Singapore, or Iowa. It asked for a video, and the server sent it back, not as one big file streaming down a pipe, but as thousands of tiny pieces, each finding its own path through the network.

Those pieces are packets. And understanding packets is the foundation of understanding everything else in this book, payments, privacy, surveillance, sovereignty. All of it rides on packets.

First, What Is Digital Data?

Before we get to packets, we need to understand what’s actually being sent.

When you type “hello” in a WhatsApp message, your phone doesn’t send the word “hello” the way you’d write it on paper. It converts each letter into a number, h becomes 104, e becomes 101, l becomes 108, and so on. These numbers are then converted into binary, sequences of 1s and 0s that electronics can handle.

A single 1 or 0 is called a bit. Eight bits make a byte. The word “hello” is 5 bytes, 40 bits. A single high-resolution photo might be 5 million bytes (5 megabytes). A 10-minute YouTube video might be 100 million bytes.

Everything digital, your messages, photos, bank transactions, Aadhaar verification requests, is ultimately a sequence of 1s and 0s. The question is: how do you get that sequence from your phone to where it needs to go?

The Dabbawala Metaphor

In Mumbai, about 5,000 dabbawalas deliver roughly 200,000 lunchboxes every single day. The system is famous for its reliability, approximately one mistake per six million deliveries.

Here’s the crucial detail: no single dabbawala carries a lunchbox from start to finish. Instead, the system works through handoffs. A dabbawala picks up your lunchbox from your home. He takes it to a local collection point. There, lunchboxes are sorted and handed to another group who take them to the railway station. A third group sorts them by destination neighborhood. A fourth group delivers them to the final office.

Each dabbawala is responsible for only their leg of the journey. They don’t need to know the full route, just their segment. The coding system painted on the lunchbox lid tells each dabbawala what to do with it at their stage.

The internet works on exactly the same principle.

So What Is a Packet?

When your phone sends data across the internet, it doesn’t open a direct connection and pour the data through like water through a hose. Instead, the data is broken into small chunks, typically around 1,500 bytes each. Each chunk is wrapped in some extra information and sent out as an independent unit.

That unit is a packet.

Think of it this way: if you wanted to send a 300-page book through the dabbawala system, you wouldn’t send the whole book as one package, it’s too heavy and unwieldy, and if it gets lost, you’ve lost everything. Instead, you’d tear out each page, put it in its own envelope with instructions on the cover, and send them separately. Each envelope can take a different route. Each one arrives independently. The recipient reassembles the pages in order.

That’s packet switching.

Anatomy of a Packet

Every packet has two parts:

The Header, The Label on the Lunchbox

The header is the metadata that tells the network how to handle this packet. It contains:

Source address, Where this packet came from. This is your device’s IP address, a unique number that identifies your device on the network. Think of it as the return address on an envelope.

Destination address, Where the packet needs to go. This is the IP address of the server you’re trying to reach. When you watch YouTube, the destination is Google’s video server.

Sequence number, Which piece of the original message this packet contains. If your video was broken into 10,000 packets, this number tells the receiver “I am packet #4,827” so it can put everything back in order.

Protocol, The rules this packet follows. The two main protocols are:

TCP (Transmission Control Protocol), Reliable delivery. If a packet gets lost, TCP requests it again. Used for web pages, messages, file downloads, anything where every piece matters.
UDP (User Datagram Protocol), Fast delivery, no guarantees. If a packet gets lost, tough luck. Used for live video calls, online games, live streaming, where speed matters more than perfection. (This is why video calls sometimes glitch, a lost packet just means a skipped frame.)

TTL (Time to Live), A counter that starts at a number (usually 64) and decreases by one at each hop. When it hits zero, the packet is discarded. This prevents lost packets from bouncing around the network forever, clogging things up like a lunchbox that never reaches its destination and just keeps riding the trains.

The Payload, The Actual Content

The payload is the actual data you’re sending, a fragment of your message, a slice of an image, a piece of a video frame. On its own, a single packet’s payload is often meaningless. It’s one page torn from that 300-page book. But combined with all the other packets, it reconstructs the complete data.

Why Packets? Why Not Just Send the Whole Thing?

This is the key question, and the answer shaped the entire internet.

The Old Way: Circuit Switching

Before the internet, we had the telephone network. When you called someone, the system created a dedicated circuit, an actual physical path of wires, between you and the other person. That circuit was held open for the entire call, reserved exclusively for you.

This worked fine for voice calls. But it was incredibly wasteful. Think about a phone conversation: there are pauses, silences, moments when you’re listening. During all of that, the dedicated wire is sitting idle. You’re paying for a reserved lane on the highway while your car is parked.

If you tried to run the internet on circuit switching, you’d need a dedicated wire between every pair of communicating devices. That’s billions of simultaneous connections. It’s physically and economically impossible.

The New Way: Packet Switching

In the 1960s, researchers including Paul Baran and Donald Davies independently came up with a radical idea: don’t reserve the wire. Instead, break the data into small packets, label each one with its destination, and let them share the wires.

Packets from different senders interleave on the same cable. Your YouTube video packets share the same fiber optic cable as someone else’s WhatsApp messages and a third person’s UPI payment. Each packet finds its way to the right destination based on its header, just like lunchboxes from different households sharing the same train and the same dabbawalas.

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. The protocols (TCP, UDP) exist to handle this chaos.

Packets in Your Daily Life

Now that you know what packets are, let’s see them in action:

Opening Instagram, You tap the app. Your phone sends a handful of packets requesting your feed. Instagram’s servers respond with hundreds of packets carrying image thumbnails, text, video previews, ad data, tracking pixels. Your phone reassembles all of these into the smooth scrolling experience you see. The entire feed load might involve 2,000-3,000 packets.

A UPI payment, You scan a QR code and pay ₹20 for chai. Your phone sends a small cluster of packets to PhonePe’s servers, which forward them to NPCI, which routes them to banks. The entire transaction might be 20-30 packets, but each one passes through multiple intermediaries, and each intermediary can see the packet headers. We’ll trace this in detail in Chapter 2.

A video call, Hundreds of packets per second fly between you and the other person, carrying compressed audio and video. These use UDP because speed matters more than perfection, if a packet is lost, you don’t want to wait for retransmission (that would cause a freeze). Instead, the call just skips ahead. This is why video calls sometimes pixelate or audio cuts out for a fraction of a second.

An online game (BGMI, Valorant), Your device sends packets containing your inputs (move left, shoot, jump) to the game server, and receives packets containing the world state (where other players are, what’s happening). This happens dozens of times per second. “Lag” is what you experience when these packets take too long to arrive. “Ping” is the round-trip time for a packet to reach the server and return.

What Packets Reveal

Here’s where things get important for the themes of this book.

Even when the payload is encrypted (and it usually is, thanks to HTTPS), the header is visible. It has to be, the network needs to read the destination address to route the packet, just like a dabbawala needs to read the lunchbox lid to know where it goes.

This means anyone between you and the destination, your Wi-Fi router, your ISP (Jio, Airtel, BSNL), an internet exchange, a government monitoring system, can see:

That you connected to a specific IP address (they may not know which exact page you visited, but they know you connected to, say, YouTube’s servers)
When you connected and for how long
How much data you exchanged (a 2-hour video stream looks very different from a quick message)
The pattern of your connections over time, what you access, when, and how often

This is metadata, data about data. And metadata is often more revealing than the content itself.

Consider: 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. The pattern of connections tells the story.

Or: we don’t need to read the payload of your UPI packets to know that you make a payment to a specific liquor store every Friday evening. The metadata, IP addresses, timestamps, frequency, is enough.

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

Try It Yourself

The Packet Tracer experiment in the lab lets you send a packet from your phone to a web server and watch it hop through each network node. Toggle the packet header to see what metadata each intermediary can read, even when the payload is encrypted.

The Foundation

Packets are the atoms of the internet. They don’t have opinions. They don’t have politics. But the infrastructure that moves them, the policies that govern them, and the entities that watch them, that’s where the story gets interesting.

Related: How UPI Actually Works traces a single ₹20 payment through India’s digital infrastructure, packet by packet. Data Localisation in India asks where these packets end up being stored.