How the Internet Actually Works: From Undersea Cables to Your Screen

Tap a link on your phone and a page appears in a fraction of a second. It feels instant and almost magical, but nothing about it is magic. Your request was chopped into packets, handed from network to network, shot through glass fibers lying on the ocean floor, and reassembled on a server thousands of miles away. The internet feels wireless, but it is overwhelmingly wired.

Follow one packet on a journey from a phone in Chicago to a server in London, and you will meet every major piece of the internet's physical machinery: the last mile, the ISP, the backbone, the exchange points, the undersea cables, and the naming system that starts the whole trip.

The last mile: your home to the ISP

Everything starts with the last mile, the connection between your device and your internet provider. For most people this is fiber to the home, a cable modem line, DSL over old telephone wiring, a fixed 5G wireless link, or a satellite dish. Fiber is the gold standard: pulses of laser light carry data through glass strands at enormous capacity, and a fiber line can deliver a gigabit per second or more to a single household.

Your home router is the first real piece of internet infrastructure you own. It takes the signal from the modem or fiber terminal, assigns local addresses to your devices, and forwards everything outward to your ISP. Wi-Fi adds a small delay here, usually a few milliseconds, which is why a wired connection still feels snappier for gaming and video calls. The last mile is also where most of the speed you pay for actually lives: once your packets leave the ISP, their pace is set by physics and distance, not by your plan.

ISPs, backbones, and exchange points

Your ISP aggregates traffic from thousands of homes and businesses and hands it to the wider internet. Big ISPs run their own long-haul backbone networks, high-capacity fiber routes linking cities. But no single company owns the whole internet. Instead, networks interconnect in two ways: they pay larger networks for transit, or they peer, exchanging traffic directly as equals.

Peering often happens at internet exchange points, or IXPs. An IXP is a building full of routers where dozens or hundreds of networks plug into a shared switching fabric and swap traffic without paying per byte. There are hundreds of IXPs worldwide, and the largest, such as DE-CIX in Frankfurt, move staggering volumes of data every second. When your ISP peers with a content network at a local IXP, your video stream may never travel farther than your metro area.

That is the secret behind the modern internet's speed: most of what you watch is cached nearby. Content delivery networks store copies of popular videos, app updates, and websites on servers inside or near your ISP's network. Only the first request, or genuinely new data, makes the full journey across the world.

The ocean crossing: submarine cables

When data does need to cross an ocean, it almost always travels by submarine cable. TeleGeography tracks 607 in-service cable systems in 2026, spanning roughly 1.5 million kilometers of ocean floor, and they carry about 99 percent of all intercontinental internet traffic. In deep water these cables are barely thicker than a garden hose; near shore they get extra steel armoring against anchors and trawlers.

The internet feels wireless, but it is overwhelmingly wired: 99 percent of intercontinental traffic travels through cables resting on the ocean floor.

Light signals fade over distance, so cables include repeaters every few dozen kilometers that amplify the signal as it crosses the abyss. Modern cables with many fiber pairs can push hundreds of terabits per second across a single system. Landing stations on each coast connect the undersea segment back to terrestrial backbones, and from there your packet rejoins the network of routers heading toward its destination.

Cables are the internet's most fragile link. Between 150 and 200 faults happen every year, and the vast majority are caused by human activity: dragging anchors and fishing nets. When a cable breaks, routing protocols steer traffic around the damage within seconds, which is why you rarely notice. Fixing the break is the slow part: with only about six dozen specialized cable ships in the world, a repair can take weeks of locating the fault, hauling the cable up from the seabed, splicing it, and laying it back down.

DNS: the internet's phone book

Before any of this happens, your device has to answer a basic question: what is the numeric address of the server you want? That is the job of the Domain Name System. When you type a web address, your device asks a recursive resolver, usually run by your ISP or a public service, to look it up.

If the answer is not cached, the resolver walks down a hierarchy. It asks one of the 13 logical root servers, which exist as hundreds of physical copies worldwide using a technique called anycast. The root points to the servers for the top-level domain, like .com, which point to the domain's authoritative servers, which finally return the IP address. Caching at every level, governed by time-to-live values, means this whole chain usually takes milliseconds and often does not happen at all for sites you visit regularly.

Only then does the real journey begin. Your packets leave your router, ride your ISP's network to a peering point or backbone, cross the ocean as light in a glass fiber, surface at a landing station, and arrive at a data center where a server assembles a response and sends it all the way back. Hundreds of devices cooperated to make it happen, most of them invisible to you. The internet is not a cloud. It is the most elaborate physical machine humans have ever built, and it runs on light, glass, and remarkably good manners between networks.

References

TeleGeography submarine cable map and FAQs. International Cable Protection Committee. Digital Watch Observatory. Verizon global latency SLA. Cloudflare.