A settlement can build a working local network from salvaged switches, twisted-pair cable and a few computers, and that network can carry file sharing, messaging, a web server and mail inside the settlement and to its neighbours. It cannot rebuild the global internet, which depended on undersea cable, carrier-grade routers, a semiconductor supply chain and institutions that handed out addresses and signed certificates. Plan at the scale of the settlement, and treat every part as a salvaged machine that someone must be able to repair.
Part of Networking
Orientation to the network-building articles: what a salvaged local network can do, what it cannot, and which article covers each step from wire to services.
A Local Network Is Recoverable And The Global Internet Is Not
The internet was never one thing. It was a continuously maintained industrial artefact: long-haul cable, routers built on chip fabrication, power and cooling at every exchange, and organisations that allocated addresses, ran the name hierarchy and vouched for web servers. Remove the maintenance and the institutions and none of it keeps running. Nothing in this section tells you how to get it back, because a village cannot.
What a village can get back is the layer underneath: machines wired together, speaking the same rules, serving each other. The concepts are the same ones the internet was made of, and the equipment is common in the ruins of any office building. The Network Fundamentals article gives the vocabulary (nodes, links, bandwidth, latency, layers). This article is the map of what to build with it, in the order to build it.
The scale is modest and the payoff is large. The carrier for this section, Internet Infrastructure, states that even 10 Mbps Ethernet can move a full book’s text in under a second. That claim holds: 1 megabyte is 8,000,000 bits, and 8,000,000 bits at 10,000,000 bits per second is 0.8 s. If a link keeps the 90-95% efficiency that Network Fundamentals gives for a healthy 100 Mbps link, the same file takes about 0.84-0.89 s. A book-length text of roughly a megabyte is therefore one second of work for the oldest Ethernet there is.
What You Need
- Machines — any computers with a network interface; the Network Hardware article covers testing salvaged ones
- Cable and connectors — twisted pair, covered from Physical Infrastructure onward
- A switch — or a computer acting as one; see Network Switches
- Software, held offline — an operating system and server programs you already have on disc or drive, because there is nobody to download them from
- Power that stays on — the Server Deployment article covers it; a network that drops with every brownout is not trusted
Method: Build Outward From One Switch
Step 1: Join two machines and make them talk Run one cable between two computers through a switch and give each an address. If one can reach the other, the physical layer and the addressing both work. Everything later is more of the same. Start with Physical Layer and Data Link Layer if you want to know why it works, and Twisted Pair Cabling if you just need to make the cable.
Step 2: Give the settlement an address plan Decide the numbering before the first machine is added. IP Addressing explains how, and why a settlement uses a private range rather than asking anyone for addresses.
Step 3: Add the services people will actually use Name lookup, automatic addressing, a web server for the shared library, mail, shared files. Core Protocols and Server Deployment cover the choices.
Step 4: Join the settlement to its neighbours A radio or fibre link between two settlements makes one larger network. Routing Protocols covers how packets find their way across it. The honest limit is that you can only join networks you can physically reach.
Step 5: Protect it and write it down Network Security covers what actually threatens a settlement network. The paper diagram and address list matter as much as any of it.
Common Mistakes
- Planning for the internet’s scale — a settlement network needs no autonomous system numbers, no carrier routing and no public addresses; copying the internet’s structure only adds parts that can break
- Treating the services as the hard part — the web, mail and file servers are the easy step; the cable, the power and the documentation fail first
- Depending on a download — if the only copy of the operating system or a server program is a link to a mirror that no longer exists, the network cannot be rebuilt after a disk failure; keep installation media and the packages you need
What’s Next
- Learn next: OSI Model — the layered picture that tells you which part to blame when something fails
- Combine with: Communication Need — decide what the settlement actually needs to move before spending cable on it