Graphs

In their most generic form, trees are graphs—directed, acyclic graphs. A general graph can be described as a collection of connected nodes, sometimes referred to as vertices, with certain properties such as whether cycles are allowed. The connections between those also have their own name: edges. These edges can have certain properties as well, in particular, weights and directions (like one-way streets).

By enforcing these constraints, a model can be built that, just like trees, reflects a certain reality very well. There is one particular thing that is typically represented as a weighted graph: the internet. While, nowadays, this might be an oversimplification, with various versions of the Internet Protocol (IPv4 and IPv6) and Network Address Translation(NAT) technologies hiding large numbers of participants online, in its earlier days, the internet could be drawn as a collection of routers, computers, and servers (nodes) interconnected with links (edges) defined by speed and latency...