Deployed Internets: A Broad Range of Possible Configurations
A single lander with an IPN gateway to a (real or virtual) internal network | |
Small number of cooperating robots on planetary surface (e.g. Single lander, single rover) | |
Orbiter-to-surface communication and coordination (e.g. sample return recovery) | |
Multiple beyond-line-of-sight missions connected by low-orbit communication satellites | |
Planet-stationary satellites for relay and gateway functions | |
Spacecraft on-board LANs | |
The Earth’s Internet |
Some Functions of Deployed Internets
Science Data and Telemetry Return | ||
Command and Control of In-Situ Elements | ||
Telescience/Virtual Presence | ||
Initially back-hauled to earth | ||
Secondarily, in support of robotic control of robotic exploration | ||
Eventually, in support of human in situ control of robotic exploration |
Differences between IPN
remotely-deployed
internets and the terrestrial Internet
Power Management is of Preeminent Importance
Power availability affects all aspects of deployed internet operation | |||
Solar conversion is the primary power source for foreseeable future | |||
Example: The average solar intensity in Mars orbit is 590 W/m2, compared with 1370 W/m2 in Earth orbit | |||
Surface-based solar panels are subject to | |||
Atmospheric dust limiting available solar energy | |||
Dust build-up on/erosion of solar panels, reducing effectiveness over time | |||
Location-based reductions in solar intensity | |||
Seasonal variations in solar intensity | |||
Efficiency of communication at all layers is required to offset the limitations of power availability |
Terrestrial “Edge” Technologies with Potential In-situ Use
A set of high-capacity, high-availability links between network traffic hubs | ||
Terrestrial backbone links are between hubs like Houston and Chicago. | ||
Interplanetary backbone links are between hubs like Earth and Mars. |
Differences Between Terrestrial and Interplanetary Backbones
Cost per second of transmission is very high, so… | ||
Don’t waste transmission opportunities. | ||
Intra-backbone connectivity might never be end-to-end, so… | ||
Don’t rely on end-to-end connectivity for protocol operations. Use store-and-forward techniques. | ||
End-to-end round trip time may vary from minutes to weeks, so… | ||
Don’t rely on negotiation or other conversational protocol mechanisms; by the time a conversation converges, the reason for it may have passed. Make protocol decisions autonomously, locally. |
Resulting Backbone Differences
There is a working prototype: the CCSDS File Delivery Protocol (CFDP). | ||
Architecturally very similar to IPN. | ||
International standard, four experimental implementations. | ||
Baselined for Deep Impact mission, potentially others. | ||
But CFDP was designed to support individual space flight missions, not to serve as the infrastructure for a permanent, general-purpose network. | ||
Addressing scheme is simple but limited. | ||
Application, transport, network, and reliable link layers are combined into a single protocol, which only does file transfer. | ||
Specification of proposed IPN protocols is under way. |
Interplanetary Dialogs:
Design Principles
Intermittent connectivity suggests an Email-like architecture | ||
Common “Handling Instructions” for a data collection | ||
Network must accommodate the persistence and transfer of state | ||
Names (not addresses) are the means of reference | ||
Names have two parts: a routing part (specifies the IPN region) and an administrative part (specifies the DNS name) |
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Routing between IPN regions based upon routing part of the name | ||
Late-Binding | ||
Separate addressing domains for each internet; administrative names converted to local addresses only at the destination IPN region | ||
Indirection | ||
Inherent dependence on intermediate relay agents | ||
Custodial transfer | ||
Intermediate nodes assume possibly-long-term responsibility for data forwarding | ||
“Bundles” as a common end-to-end transfer mechanism |
Bundling Spans Temporal Discontinuities Between Networks
Single Name
Space,
Late Name-to-Address Binding(s)
The Interplanetary
Internet:
An overlay network for
interconnection of regional internets
A region is an area where the relevant characteristics of communication are homogeneous | ||
One can define regions that are based upon: | ||
Communications capability | ||
Quality of Service Peerings | ||
Security (levels of trust) | ||
Degree of resource management | ||
Etc. | ||
Traversal of two or more regions will effect the nature of communications |