The Inter-Area Traffic Network, or simply IATN, is an established system of traffic schedules descended from the much admired Transcontinental Corps or TCC. Modern open-source parlance might refer to it as a fork from the original project and it’s an apt description.
IATN is a group of highly skilled “ironman” operators who meet to relay messages between areas. Communications circuits are typically high-speed radiotelegraphy, a real treat for cw ops who will be amazed at the speed and efficiency on display.
FM-001 Traffic Operations describes IATN this way,
The IATN is an established system of traffic schedules managed by area managers. These nets employ a group of highly skilled operators who meet to relay messages between areas. These communications circuits are typically high-speed radiotelegraph circuits or part of the Digital Traffic Network (DTN). For example, a message from New York to California, after reaching the RRI East Net, would need to be transmitted to the Western Area Net (RRIW) via an IATN schedule before it could be passed down the Western Area Net-layers to its destination for subsequent delivery.
In many ways, IATN circuits are throwbacks to the trunkline system predating NTS’s formation in the 1950s. Here are two RRI white papers considering a contemporary implementation of trunklines: