Cables and services: what drives what? --- Eduardo, great question: "The physical layer design follows the transport and content layers, or the other way around?"

Initially, the cables (esp. Europe to America) followed the old telegraph cables; further developments obviously went hand in hand with the development of services - telephone and later telecoms - which were dominant in US, and then Europe.

These days internet is used all over the world - but the major chunk of data flows mainly between US and Europe still. Why? Among other because the public cloud - which we all use - is mainly located in the US and Europe (and it is, in turn, hosted there because of the good backbone, but also because of other economic, legal and political circumstances).

As cloud hosting is being diversified - for both economic reasons (content delivery networks, or CDNs, host place copies of the most wanted content closer to users around the world) and political (many countries push for 'data localisation) - we may see greater development of fibre in developing countries as well, to support this diversified infrastructure.

PS Note that this map shows submarine fibre only; there is, of course, the entire structure of terrestrial cables buried under the ground as well, which is not shown - but it is commonly national or regional rather than international, shorter and with lower bandwidths but with greater redundancy/multiple cables, and of course less exposed than the submarine ones.

Source author: Vladimir Radunovic vladar@diplomacy.edu