When you really need to get a signal in from Pluto, a direct connection isn’t always possible. Oh sure, when it’s a big project like New Horizons, you can make sure the line is clear and someone’s listening — but for routine updates from a Neptune orbiter or power-starved comet lander, there’s Delay/Disruption Tolerant Networking, which just got its first big installation on the International Space Station.
What’s DTN? Glad you asked. It’s a protocol suite made to be resilient even in the face of huge interruptions of connectivity — for example, when an entire planet or star passes between two nodes on a network.