How do IP packets know what hoops/servers to go through to reach the intended recipient’s IP?
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On the lowest levels, “hierarchical” routing is used. Computers, that are connected to the same router, get IP addresses with the same top digits and only differ in lower digits. So if the router sees, that the top digits don’t match – it knows that the destination is not in “his department” and sends it to a superior router. If the digits match – then it just walks the list of subordinate IPs, until there is a match.
On the highest level, a different approach is used. All top routers have a list of other top routers. They also have a map of the Internet, which tells how those top routers are connected to each other, the speed of the connection, etc. They first pick a router that is servicing the destination (by comparing the top digits of IP with a list), then they use a map to plot the best path, and then send.
The map of the Internet is updated automatically. When a new top router joins, it announces itself to the neighbors. The neighbors then tell their neighbors, and so on. When some router disconnects, its neighbors notice and report to others.
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