UEG Inter-Colonial Message Relay Network

The UEG Inter-Colony Message Relay Network, abbreviated the ICMRN and known colloquially as Mir-Net, was a civilian cross-colony communications network utilised by the Unified Earth Government from the 2390s onwards. Planetary artificial intelligences would collate global outgoing traffic and allocate it to outbound civilian craft based on their listed destination. On arrival, the AI present at that colony would retrieve the traffic and distribute it to the intended recipients. The entire process was automated and did not require required (or indeed, accept) any input from the crews and passengers of the carrier vessels, and occupied only a tiny portion of civilian ships' memory and physical space.

History
Early interstellar communication was accomplished through the Colonial Administration Authority Postal Service, a civilian organisation dedicated to collecting and delivering electronic communications between colony worlds. First established in 2365 to ferry messages between Earth and Reach, the Corps soon expanded in ships and personnel to service the UEG's exponentially growing number of colony worlds. The Postal Service rapidly became financially unsustainable in attempting to keep pace with the explosion in colony worlds and electronic traffic between them, and was replaced in 2395 by the Inter-Colony Message Relay Network. The Postal Service was disbanded, but its concept was adopted by the UNSC Navy in its unmanned communications vessels.