Time required: One hour
When data is sent across the internet, it rarely travels in one big chunk. Instead, every email, photo or streamed song heading your way is chopped down into smaller pieces, called packets, which bounce from one server to the next until they reach your PC.
There’s no guarantee they’ll all take the same route, nor that they’ll arrive in the right order. Some may take a more convoluted route than others, while some servers might not be so quick at handing off the packets it receives to the next server in the chain.
Therefore, each packet carries additional data, a bit like the address on an envelope, that makes clear which other packets it goes with, and where it fits in the overall collection. Your computer uses this data to reconstruct the original file or stream, before sending it on to the email client, photo viewer or audio player that requested it.
It works very well, for the most part, and pictures and messages routinely arrive uncorrupted, in a timely manner. Every so often, though, packets can get lost along the way, or may be so delayed that they miss their slot. The latter of these issues isn’t really a problem with emails,
