The ideal way to build a national broadband network for access to the Internet would be with a high-bandwidth, bidirectional cable running to each individual household. But sometimes you have to work with what you’ve got, and in America, what we have are cable TV networks. These networks have the bandwidth, but not the bi-directional part—they weren’t originally intended for two-way communication. Worse, the cables for many neighbors all connect together, so it’s not possible to send a signal to just one household. And yet, cable companies manage to provide 100 Mbps bandwidth to their broadband customers using this flawed infrastructure, and they do it without compromising the preexisting cable TV service. The tech behind this magic trick goes by the name of DOCSIS, which stands for Data Over Cable Service Interface Specifications.
I never really knew how DOCSIS worked under the hood until I saw this article. Good stuff.