Wirebook › Glossary › Store and forward
What is store and forward (where does a message wait)?
In one sentence: Passing a message on by keeping a copy at each stop and sending it to the next one only when that next step is ready, so nothing is lost if the far end is away.
A little more
Store and forward means each stop along the way keeps a full copy of a message and only passes it on when the next step is ready. Text messages work like this (the message centre holds a text until the phone is reachable), and so do email (servers hold mail for each other and retry for days) and chat apps (the server holds a message until the other phone comes online, then your second tick appears).
It's the opposite of a live phone call, where both ends must be there at the same moment. The cost is that a stored message can be late, and the middle can't hold it forever: each service gives up after its own waiting time and may tell you it was not delivered.
See it in action
- BonusHow does a text message find its way to someone's phone?Send a pretend text as a frog: it hops by radio onto a lily pad (a phone tower), rides underground pipes to the message centre, which looks up where your friend's phone is, then hops off the lily pad next to them.8 min · interactive
- BonusDoes the app keep peeking, or does the website ring a doorbell?How does a news app know a new lesson appeared? Race a peeker, a messenger who waits at the door and a doorbell through a pretend day, count the wasted trips, be the peeker yourself, and peek at this site's real feed to see a 304 Not Modified.6 min · interactive
- BonusWhy can a download pick up where it left off?Break a pretend file into numbered pieces, interrupt the download, and compare restart-from-zero with resume-using-byte-ranges.6 min · interactive
Do it for real
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