AP Computer Science Principles Unit 4 Essentials

The Internet is a network of networks in which every device has a unique IP address. Data is broken into packets that are routed independently across shared paths — a scheme called packet switching — and reassembled at the destination. This all works because devices follow common protocols (like TCP/IP, HTTP, and DNS), which are the agreed rules that let very different systems communicate reliably.

Parts of any network eventually fail, so reliability comes from fault tolerance — the ability to keep working despite failures. The Internet achieves this through redundancy: duplicate connections and multiple paths between devices. If a router or route goes down, packets can travel a different way, so the network as a whole keeps functioning. This design is a major reason the Internet is so robust and scalable.

To finish large tasks quickly, work can be divided. Parallel computing runs parts of a program at the same time on multiple processors, while distributed computing spreads a problem across multiple networked computers. Speedup measures how many times faster the parallel solution runs than the sequential one — but it is limited, because some steps must run in order and coordinating the pieces adds overhead.