Hello everyone. I am interested in learning about the history of computer networks. I've become interested in this area for two reasons. First, I realized that the ability to enter a random url and be served content from a world away is nothing short of magic, and I would like to better understand it. Second, there are several very large and important companies in the history of technology, including Cisco, Juniper, Broadcom, Qualcomm, who were involved in creating the equipment and chips which enabled such magic. Despite this, there are fewer good histories of these companies than for other SV companies.Context - I am not a computer scientist by training; I work in biopharma, but have a rudimentary understanding of code.My overarching question is as follows. In ~1985, Local Area Networks were proliferating and the Public Switched Telephone Network had digitized, in that the signal in the network (except for the local loop) was digital PCM-voice running on time-division multiplexed copper circuits (increasingly replaced by fiber). However, the PSTN was still a circuit-switched network. How did we graft an all-IP,packet-switched network on top of this framework?Specifically, I'm interested in, the evolution of WAN protocols (eg, Frame Relay, ATM) and how they were replaced by IP networks, the history of the equipment needed to make these markets work, and the history of how ISPs built these networks.