The internet is often described simply as “a network of networks,” but that barely begins to capture how all the pieces—servers, switches, providers, access networks and packet routing—fit together to allow you to send an email or watch a video in real time. In this article we’ll explore how the internet works from the ground up: how users connect from local networks into global infrastructure, how the hierarchical structure of ISPs functions (with Tier 1, Tier 2, Tier 3 distinctions), how autonomous system numbers work, and finally how your data packet travels end-to-end through different access technologies.

A Vast Network of Networks

At its heart, the internet is exactly what the name suggests: a network of networks. It is comprised of countless local networks (such as home WiFi or office LANs), regional and national backbones (owned by Internet Service Providers or ISPs), and global infrastructure (such as under-sea cables and major backbones). These individual networks interconnect so that data can flow seamlessly from one point in the world to another, across continents and through many network hops.
When you load a website or send an email, your request travels out of your local network, through your ISP, potentially across several backbones and peer networks, and eventually reaches the destination server. That server then sends back a response via a similar path. All of these networks must speak the same protocols and interconnect cooperatively in order to make the internet work.

How Users Connect: From Local to Global

From your vantage point as a user, connectivity starts in a very local environment: your home router, mobile phone, or office switch. These devices connect to an access network run by an ISP. That access network then uplinks into larger regional or national networks, and ultimately to global networks.
For example, you might connect via a fiber-to-the-home link in your neighborhood, or via mobile 5G on your smartphone. Your local access network hands off your traffic into the broader ISP network, which in turn peers or transits with larger carriers to cross borders and continents. That is how your local action—clicking “send” on an email—becomes a global journey.
The structure of these connections often reflects a hierarchy of Internet Service Providers which we’ll discuss next.

The Hierarchical Structure of ISPs: Tier 1, Tier 2 and Tier 3
One way to understand how the internet works at scale is to look at the hierarchy of ISPs: Tier 1 at the top, then Tier 2, then Tier 3.
*Tier 1 ISPs are at the apex—they operate global backbones that can reach the entire internet without paying for transit to any higher-tier provider. In other words, they are settlement-free peers among themselves. Wikipedia+1 Examples of Tier 1 networks include AT&T in the US, NTT Communications in Japan, and Tata Communications in India.

*Tier 2 ISPs connect to Tier 1 networks (via paid transit) and peer with other Tier 2s. They serve large regions or national markets but do not have universal settlement-free reach.

*Tier 3 ISPs are typically local access providers to end-users. They purchase transit from Tier 2 or Tier 1 networks and do not peer broadly.

This hierarchy matters because it determines how many hops your data must traverse, how many networks your traffic will cross, and how resilient or performant your connection might be. In effect, understanding which tier your ISP belongs to helps you understand how the internet works behind the scenes.

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Autonomous System Numbers (ASNs)

Another crucial piece in “how the internet works” is the concept of an autonomous system (AS) and its autonomous system number (ASN). An autonomous system is a group of IP prefixes managed by one network operator under a common routing policy. Each AS is identified globally by an ASN, which is used in the Border Gateway Protocol (BGP) to exchange routing information between ASes.
When your ISP routes traffic, it informs its peer ASes and transit ASes about the IP prefixes it can reach. The ASN makes the routing tables manageable and globally unique. So when you send data across the internet, you are in fact traversing a series of AS hops, each announced via BGP, until you reach the destination AS. Without this mechanism the internet would not scale effectively.

Access Networks: How People Actually Connect

When we ask how the internet works at the user side, we must consider the variety of access network types through which users connect. These include:
Mobile wireless access: 3G, 4G LTE, 5G connecting smartphones or mobile hotspots.

*Fixed wireless: point-to-multipoint radio links from a provider to a premise.

*Twisted-pair copper (DSL): the traditional phone line running Digital Subscriber Line technology.

*Hybrid fibre-coaxial (HFC): cable networks common in many cities.

*Fiber to the Home (FTTH): full optical fibre to a residence, offering the highest speeds.

*Satellite broadband: including geostationary (GEO) satellites and newer low-earth orbit (LEO) constellations.

Each of these access types hands your traffic into a local network, which connects to a regional distribution network, and ultimately to the backbone. For example, your smartphone may connect via 5G to a local cell-tower base station, then into the carrier’s core network, whereas a home fibre user’s router connects directly into a local fibre distribution hub.

Tracking a Data Packet: From User to Destination

To fully answer how the internet works, let’s trace what happens when you send an email (or upload a file) from your device to a server, through one of the access types above. We’ll simplify the steps:
Modulation into digital bits: You compose an email on your laptop. The device encodes the message into digital data (ones and zeros) and passes it to your home router or mobile modem.

Local network hand-off: From your home router (or mobile modem) the data flows via your access network (e.g., fibre, DSL, cable, 5G). It is encapsulated in frames/packets and travels to your ISP’s first hop.

IP addressing and routing: Each packet is given a source IP (your device) and destination IP (the email server). The router directs the packet into your ISP’s network. Intermediate routers examine the destination IP, consult routing tables (which use ASN/BGP announcements), and forward the packet across networks.

Crossing networks: Your packet may traverse multiple ASNs and ISP tiers. For example, your regional Tier 2 ISP hands traffic to a Tier 1 backbone, across the ocean via under-sea fibre, into another regional network in the destination country. At each hop, routers read the IP header, decrement the hop count (TTL), and forward toward the destination.

At the destination access network: Eventually, the packet reaches the ISP of the server, enters their data centre network, and is delivered to the server’s interface. There the bits are reassembled into the email and stored.

Demodulation / reception: The server processes the packet’s payload, the email becomes visible to the recipient. If a reply is sent, the process reverses.

In each step, the internet works because networks interconnect, IP addresses provide end-to-end identification, ASNs allow efficient routing between networks, and access networks bridge the gap between user and backbone.

Why This Architecture Matters

Understanding how the internet works helps explain several real-world phenomena:
Why your home internet speed depends on your access network type (fibre vs DSL vs satellite).

*Why latency rises when your traffic crosses continents (more network hops, longer physical distance).

*Why some ISPs charge differently for transit or peering (their tier level and business model).

*Why outages in one backbone provider can disrupt large parts of the internet (failure in a Tier 1 backbone or major ASN).

*Why newer access types such as FTTH and LEO satellite are changing connectivity dynamics—bringing higher speeds and lower latency closer to users.

Conclusion

So when you ask “How the Internet works”, the short answer is: it’s the result of millions of devices and networks, from your home router to giant global backbones, all interconnected via common protocols, IP addressing, ASNs, and layered ISP hierarchies. Your device sends a packet, which is modulated into digital signals, carried over whatever access network you use (mobile, fibre, DSL, satellite), traverses routers using IP addresses and ASN-driven routing, through Tier 3, Tier 2 and up to Tier 1 networks, and finally arrives at its destination where it is demodulated and processed. Understanding that full chain gives you a clearer picture of what happens in the blink of an eye each time you surf the web, send a message, or stream a video.

Whether you are using fibre in a city, DSL in a suburb, or a LEO satellite in a remote region, the same core architecture underpins your connection. That is how the internet works—efficiently, globally, and remarkably seamlessly.