Computer systems and networks
Connect computers and share work
Distinguish packets, routing, fault tolerance, and parallel processing.
Algorithm examples use AP reference notation, including one-based list indices.
A message crosses many networks
The internet is a network of networks. Devices use agreed protocols so machines made by different organizations can communicate. A message can be split into packets that travel through routers and are reconstructed at the destination.
DNS associates a domain name with address information. Routing chooses where to send a packet next. Redundant connections provide alternative paths when one connection fails, but they do not guarantee that every service remains available.
- 1Sender
- 2Router
- 3Router
- 4Receiver
Parallel work has limits
If four independent jobs each take two minutes, one processor takes eight minutes and four processors could finish in two minutes before overhead. If one job must wait for the result of another, that dependency limits the speedup.
Distributed computing uses multiple networked computers. Communication and coordination have a cost. Compare the whole execution time, including the sequential part, rather than assuming that twice as many processors makes every program twice as fast.
Check yourself
Why can an additional network path improve fault tolerance?Show answer
A packet may have another route when a connection fails. The alternative must still connect the required devices.
References used to build these lessons
We used these official documents as references when building this course's lessons. They are the sources for the syllabus structure and course requirements.
College Board · Effective fall 2023