Here’s a highly simplified list of major telecommunication networks people have built, in somewhat historical order: mail service, telegraph, telephone, radio, television, the internet.

Surprisingly, the physical mail service and the internet have something in common, which sets them apart from all the other “advanced” networks. They are agnostic to what they’re transporting. Whereas the telegraph can only transport telegrams and radio send radio transmissions, the internet, in particular, can be adapted to send most anything - mail, files, voice, TV etc. About the only thing it can’t transport is physical goods, and that’s where the mail service comes in.

It is also a testament to the power of communication, that such massive infrastructure projects as the telephone or televsion were constructed, to send essentially one type of signal, fulfilling a single function. However, as the internet evolves, it makes less and less sense to have dedicated networks for a particular type of message, and more and more sense to overlay them on the general communication network.

Indeed, Skype & most messaging apps, Netflix & internet video sites, are basically doing just this, but coming from the application side, rather than lower on the stack. There’s also more general approaches, such as VoIP, IPTV etc.