Network connectivity is often an issue on a local scale: one router or modem or device breaks. However, large operations are not immune: routing connections, as mentioned earlier, rely on the ability to communicate with at least one ``neighbor'' on the network, which is fine until that neighbor goes down. And in centralized systems, such as commercial ISPs', that's exactly what happens: any sort of problem can tank an entire area's coverage for hours to days.

\sinclude Combinatorics Applications:net-apps