Technical analysis and engineering reference.
TCP/IP fundamentally relies on end-to-end continuous bidirectional connectivity. A 3-way TCP handshake between Earth and Mars (where light travel time ranges from 4 to 24 minutes one way) would take over an hour just to establish a connection before any payload byte could be transmitted. Furthermore, planetary rotation and solar conjunctions induce frequent, prolonged link disconnects.
Delay-Tolerant Networking (DTN), codified in RFC 9171 as the Bundle Protocol Version 7 (BPv7), introduces asynchronous custodial transport: - Spacecraft store entire bundles in non-volatile flash memory rather than dropping packets when the next-hop node is not in sight. - When an optical or radio contact window opens, the sending node transfers custody of the bundle to the receiving node. - The receiving node assumes full storage responsibility, freeing the transmitter to discard its copy.
Within terrestrial LEO constellations, DTN provides resilience during cross-seam transitions, solar coronal mass ejections, and ground station cyber outages, guaranteeing 100% data delivery without relying on fragile end-to-end TCP acknowledgments.