Autonomous systems, BGP and the paths traffic takes.
Which networks originate the most IPv4 space in Portugal, which AS numbers MEO, NOS, Vodafone and NOWO use, where they interconnect and how much of the routing is protected by RPKI.
The protocol that ties networks together: prefixes, AS paths, how traffic finds its way, and why RPKI makes the internet safer.
What your provider actually does, where it gets IP addresses, why a lookup may show another name than the brand you pay, and what it can see.
The internet is about 80,000 independent networks agreeing to carry each other's traffic. Each one has a number. Here's what it means.