Just saw [this post](https://www.instagram.com/reel/CrivNA3LNel/?igshid=YmMyMTA2M2Y=) and I know it’s a very oversimplification, but what are these cables and what do they exactly do ? And who repairs, manages these cables.
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The Internet is a network, those cables provide a communication between various services but they don’t necessary forward your traffic.
When you visit a website major parts of it (like the scripts and images) are served by CDN, a content distribution network, that is hosted somewhere close to you. You ask that server for the image on Reddit post and if it doesn’t have it stored then it calls the actual reddit server and gives it you. That way the image is transmitted only once over the transatlantic cable no matter how many people in your area view it. Only when you actually do some change like posting a comment it may be transmitted somewhere far away.
The big websites (like Facebook) are fragmented and keep their local stuff local so the selfies of your coworkers may be kept on servers in your city but when you want to check on your distant relative the images will be transmitted from far away.
The popular streaming services even keep their servers in your ISP so when you watch a popular movie it may be transmitted from somewhere down the street instead of somewhere further (but not far away, they also keep stuff on country level, national level and so on). That also means they will recommend you watch something that is popular in your area. The ISP and the streaming service are both happy because they have to pay less for the transfer costs.
In the days before https was on every website everyone could cache the websites. So even in very small communities like a dorm there could be a server set up to cache the content of popular websites. If a hundred students would check a popular news site every morning you could just make a one web request to it and then serve it locally to save bandwidth.
As of 2022, it’s almost 500 cables. Those cables are only direct connections from overseas country to overseas country. The connections *within* a country are numerous, and if two countries have land-based borders, it’s likely that there are multiple network connections across those borders. There are also satellite-based connections that aren’t mapped which tend to be slower. It’s all part part of making the internet resistant to damage (earthquakes, war, inadvertent backhoe use, etc.)
The latest map of the oversea cable network is here: [https://submarine-cable-map-2022.telegeography.com](https://submarine-cable-map-2022.telegeography.com)
Some of the connections are owned by governments. Others are owned by companies. There’s probably one or two that are owned by actual individuals. Management depends on how they “important” they are. There are government-owned mission critical connections that are either managed by that country’s civil defense forces or by independent contractors. The ones owned by companies are either managed by the company itself or farmed out to contractors. Usually it’s a mix. And the ones owned by individuals are likely maintained by whoever has the contract to maintain it.
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Imagine the internet as a bunch of libraries. When a book is printed it can be shipped to multiple libraries. The more popular it is the more libraries it is sent to so the more likely a library close to you has the book. When you want a book you go to the nearest library that has it and check out the book. If it’s a popular book you’ll likely have to travel less than a rarer book to find it. Since the libraries are fixed locations there is a relatively smaller number of paths needed to ship the books to various libraries. The much larger number of paths if between the libraries and individual users. Also books can be transferred between libraries for you to pick up from closer libraries. This is done through the smaller number of routes between libraries.
The internet works in similar ways. There are a bunch of servers which are like the libraries. They store the webpages which are like the books. A webpage will be stores on multiple servers with the more popular ones being on a larger number of servers. When you enter the website into your browser is sends a request which looks for the nearest server with that website. If there aren’t close ones it can be sent from farther servers to the closer ones like a book being transferred from a farther library to a closer one. You then get the website from that closer server.
You need fewer connections between the servers since they’re smaller in number and fixed locations. The larger number of connections needed is between the servers and customers. That way you don’t need direct connections to far servers overseas. Data from the overseas server is sent to the closer server and then to you.
Imagine the internet as a bunch of libraries. When a book is printed it can be shipped to multiple libraries. The more popular it is the more libraries it is sent to so the more likely a library close to you has the book. When you want a book you go to the nearest library that has it and check out the book. If it’s a popular book you’ll likely have to travel less than a rarer book to find it. Since the libraries are fixed locations there is a relatively smaller number of paths needed to ship the books to various libraries. The much larger number of paths if between the libraries and individual users. Also books can be transferred between libraries for you to pick up from closer libraries. This is done through the smaller number of routes between libraries.
The internet works in similar ways. There are a bunch of servers which are like the libraries. They store the webpages which are like the books. A webpage will be stores on multiple servers with the more popular ones being on a larger number of servers. When you enter the website into your browser is sends a request which looks for the nearest server with that website. If there aren’t close ones it can be sent from farther servers to the closer ones like a book being transferred from a farther library to a closer one. You then get the website from that closer server.
You need fewer connections between the servers since they’re smaller in number and fixed locations. The larger number of connections needed is between the servers and customers. That way you don’t need direct connections to far servers overseas. Data from the overseas server is sent to the closer server and then to you.
the “just 400” cables each bundle several fibre optic fibres, for example [this new cable between north America and Japan](https://cloud.google.com/blog/products/infrastructure/topaz-subsea-cable-connects-canada-and-asia):
> The width of a garden hose, the Topaz cable will house 16 fiber pairs, for a total capacity of 240 Terabits per second
240 terabits is “how much” goes through that cable. but what does that mean again? 240.000 gigabit is 240,000,000 megabit is 240,000,000,000 kilobit.
a nice video stream needs up to 14,000 kilobit.
how many of these fit through that cable? 240,000,000,000 ÷ 14,000 ≈ 17,143,000 seventeen million different 4k video streams. or, same math but other resolutions: HD 1024p 34 million, hd720p 70million
that is, eli5, _a lot_ lot.
[not eli5 video bandwidth needs table](https://support.video.ibm.com/hc/en-us/articles/207852117-Internet-connection-and-recommended-encoding-settings)
long story short: even though existing cables each provide less capacity (e.g. “only” four fibre pairs), all ~~400~~ 500 of them together provide enough “data highway” for the world.
sibling comments have provided insight into who operates them, and how they are put there and so on.
the “just 400” cables each bundle several fibre optic fibres, for example [this new cable between north America and Japan](https://cloud.google.com/blog/products/infrastructure/topaz-subsea-cable-connects-canada-and-asia):
> The width of a garden hose, the Topaz cable will house 16 fiber pairs, for a total capacity of 240 Terabits per second
240 terabits is “how much” goes through that cable. but what does that mean again? 240.000 gigabit is 240,000,000 megabit is 240,000,000,000 kilobit.
a nice video stream needs up to 14,000 kilobit.
how many of these fit through that cable? 240,000,000,000 ÷ 14,000 ≈ 17,143,000 seventeen million different 4k video streams. or, same math but other resolutions: HD 1024p 34 million, hd720p 70million
that is, eli5, _a lot_ lot.
[not eli5 video bandwidth needs table](https://support.video.ibm.com/hc/en-us/articles/207852117-Internet-connection-and-recommended-encoding-settings)
long story short: even though existing cables each provide less capacity (e.g. “only” four fibre pairs), all ~~400~~ 500 of them together provide enough “data highway” for the world.
sibling comments have provided insight into who operates them, and how they are put there and so on.
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