Week 7: Networks Are Paths, Not Magic

A network message does not teleport from one application to another. It is wrapped in protocol information, placed on a local link, forwarded across one or more paths, and delivered to a receiving process.

This week builds a network model from the inside out. You will separate local-link evidence from routed-path evidence, read source and destination fields without pretending they tell the whole story, and diagnose a fictional reachability failure from supplied system state.

This week

1. A Packet Has Context at More Than One Layer — relate application data, transport, IP addressing, and local-link delivery.
2. Routes Decide Where a System Tries to Send Traffic — read a routing table and distinguish destination, next hop, interface, and default route.
3. Reachability Is a Chain of Dependencies — correlate address, route, and packet evidence to explain one bounded network failure.

Evidence artifact

Create a Network Path Evidence Record with a host model, route decision, supplied packet summary, failure hypothesis, corrective change in the fictional model, retest, and limitation.