It is the near future. After a major world war and limited nuclear exchange, the nations of Earth have consolidated into a few blocs. The threat of further war and the cumulative damage to the planet spur enormous private investment in colonization of space. Floating colonies surround Earth and near-Earth orbits of Sol. The terraforming of Mars has begun. A great demand for resources off-Earth has spread asteroid mining operations throughout the solar system.
A great number of factions have developed in space. No one faction has enough resources to build a communications system spanning the entire inner solar system, especially considering that deployment cost of communications nodes is high (rockets are expensive). The competing factions settle on developing a collaborative communications system modeled on the Internet, where no one faction can be dominant.
The Internet Protocol Suite (with Link, Internet, and Transport layers) works well on Earth, where static computers are connected to each other by cables. The cables allow near-instantaneous communication, and the hardwired connections are rarely changed. On an interplanetary scale, two major problems arrive.
Sparse connections: Cables on earth are cheap, but satellite dishes that work over AU distances cost a lot of money, so there are a limited number of connections each node can have. Also, connections can be blocked, based on position relative to planets and the sun. Two nodes may be unable to communicate for hours or days at a time. Importantly, much of the disruption is scheduled, due to easily predicted rotation and orbital characteristics. A good protocol suite will have a built in ability to optimize the physical transfer path from node to node to ensure data gets to where it is going as quickly as possible, and so that two way communications are not interrupted needlessly.
Latency - Message travel time from one side of the asteroid belt to the other take about 45 minutes. From Earth to mars at closest approach is about 3 minutes. This is a significant when it comes to a TCP/IP or SSL handshake. Protocols should minimize the need for two way communications without sacrificing security. Also, if packets in the same TCP session took two different routes from point A to point B; on Earth this is negligible time difference, but in space they could arrive minutes, or even hours, apart.
Statement of Work
What is the smallest set of changes you can make to the TCP/IP protocol suite to optimize its performance over interplanetary networks?
The goal is to optimize reliability, throughput, and to minimize unnecessary latency.
- Currently, humanity is limited to the inner solar system (out to the Asteroid Belt). However, the developed protocol should be extensible at least to the Kuiper Belt, with latency times of up to 10 hours.
- This question is focused on the Data Link, IP, and Transport layers; assume the physical layer works just fine.
- Here is a report on Space Communications Protocols, though this is for near-Earth space. Here is a discussion of some problems with interplanetary communications.