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Laptop to server: every hop reads the address
A network moves data as addressed packets, passed hop by hop. Say your laptop opens example.com. The request leaves over Wi-Fi to the home router, then the ISP router, then the web server. Every device along the way reads the address.
Step 1: turn a name into an address
Routers don't understand example.com. They only forward by IP address. So the laptop first asks a DNS server, which works like a phone book and answers with 203.0.113.10, an illustrative address. Only then does the laptop send its GET request to the web server.
Step 2: layers wrap data like nested envelopes
The HTTP request never travels alone. TCP wraps it with ports and ordering, IP wraps that with source and destination addresses, and the Wi-Fi frame carries the whole bundle one local hop. Envelopes inside envelopes, each layer adding its own header.
Step 3: routers forward, and reroute around failures
Each router reads only the destination IP and picks a next hop. If the link from Router A to Router B goes down, Router A sends traffic through Router C instead. TCP resends anything that was lost, so the page still loads.
While loading example.com, one router on the path suddenly goes offline. What usually happens next?
While loading example.com, one router on the path suddenly goes offline. What usually happens next?
- Packets take another path and TCP resends losses
- The connection to every website stops permanently
- Packets wait at the broken router until it returns
While loading example.com, one router on the path suddenly goes offline. What usually happens next?
Packets take another path and TCP resends losses. Routers only care about the destination address, so neighbouring routers pick a different next hop when a link disappears. TCP notices missing packets and sends them again. The page may load a little slower, but it still arrives, as long as some alternate path exists.
- Packets take another path and TCP resends losses
- The connection to every website stops permanently
- Packets wait at the broken router until it returns
Name, address, wrap, forward
Name, address, wrap, forward. DNS turns the name into an IP address, headers wrap your data in layers, and routers forward packets hop by hop. Recovery only works if an alternate path exists.