Deployed Internets in the Interplanetary Internet by pptfiles


									Deployed Internets in the Interplanetary Internet

Robert C. Durst MITRE October 25. 1999

What is a deployed internet in the IPN?
 We differentiate between the “long-haul” backbone and

deployed networks that have round-trip time characteristics closer to those for which the Internet was designed
 Any network that has the following attributes is considered a

deployed internet: - Is connected via interplanetary backbone to another network - Has an environment that does not inherently preclude the use of (possibly enhanced) Internet protocols - Uses the Domain Name space as a common means of referencing objects and systems across deployed internets

Deployed Internets Have 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 loworbit 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 Finally, in support of human in situ control of robotic exploration

Differences between IPN deployed internets and the Terrestrial Internet
T e rre s tria l “ W ire d ” Pow er a va ila b ility S ig n a l-to N o is e R a tio s In fra s tru c tu re T ra n s m is s io n m e d iu m D e p lo ym e n t $ O p e ra tio n s $ R e p a ir, U G $ N o t c ritic a l F ib e r c le a n T e rre s tria l “M A N ET” Im p o rta n t Low SN R f(p o w e r, n o d e d e n s ity) D e p lo ya b le , m o b ile F re e s p a c e R F , IR M o d e ra te TBD TBD D e p lo ye d “ W ire le s s ” O f o ve rrid in g im p o rta n c e V e ry lo w S N R f(p o w e r) D e p lo ya b le , m o b ile , s a te llite -b a s e d P rim a rily fre e s p a c e RF H ig h , f(w e ig h t) TBD V e ry h ig h

F ix e d F ib e r, c o p p e r R e la tive ly lo w R e la tive ly lo w R e la tive ly lo w

Effects of these differences, by layer Layer 0: Not in the communication model
 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


The Good News Is ...
Much of the ongoing work in mobile ad hoc networking is interesting, relevant, and timely

Physical Layer
 Spectrum management

- There’s no FCC for deployed internets - spectrum
coordination still necessary - 400MHz very popular due to diffraction effects (facilitates some beyond-line-of-sight comm) and moderate free space losses  Tracking antennas Need vibration-tolerant phased-array antennas for wideband communication to low-orbiting satellites from mobile nodes traversing rough terrain (albeit slowly) -Potential contributions by LEO-constellation vendors to support on-the-move users


Link Layer
 Management of very low signal-to-noise ratios is of

significant importance Unclear what coding schemes are best  Convolutional - limited delay  Concatenated (e.g. Reed-Solomon) - clean or out  Turbo Codes - operation in very low SNRs, but never quite clean, plus typically long code blocks Ability to apply different coding regime to packets based on their QOS requirements may become very important  Resource reservation at MAC layer may be of significant importance Closed loop control of remote resources may require resource coordination at multiple layers, including interference avoidance at link layer



Link Layer (Continued)
 Resource constrained environments require cooperation at

all layers Link layer entities must sense their own status and signal it to upper layer entities for appropriate adaptation  Link availability  Link capacity and congestion status  Current error conditions


Network Layer
 Deployed internets will be comprised of fixed (e.g. landers)

and mobile elements Mobile elements can be slow-movers  Rovers  Balloons - Mobile elements can be fast-movers  Low orbiters  Powered “Air”craft - Routing protocols must be able to constitute and maintain an ad hoc network with all of these elements - Must efficiently adapt to changes in available link resources -- “vertical handoffs?”  Must propagate signals of current conditions issued by link layer elements


Network Layer (Continued)
 Resource allocation in dynamic environment

- Integrated services model? With reservation range rather
than fixed operating point (supports signaling from lower layers) - Must adapt to changing conditions in link layer, and not over-allocate resources in some nodes when others cannot support  Self configuration - Address allocation and management in the absence of fixed infrastructure is required - Potential requirement for self-organization into hierarchies as network expands or aggregates separate subnetworks - Applicable technology currently being developed for sensor networks

Transport Layer
 Participation in power-efficient communication schemes

- Need to carefully consider the trade-offs between coding
at the link layer and retransmission at the transport layer to optimize use of overall communication resources may dictate mixed-loss operation at transport  Adaptation to changing network conditions - May require QOS-responsive reliable transport Efficient accommodation of link outages - Explicit congestion signaling and prompt response - Robust error trend indication with appropriate response  Data rate asymmetry in in-situ satellite communications Must be able to accommodate >100:1 asymmetries  Without degrading use of the high-rate side  While still performing useful functions on the :1 side



Application Layer
 Service location in mobile ad hoc networks

- Dynamic assignment of all system services - Election of replacement system providers in the event of
system failure or network partitioning - Subject of ongoing, potentially relevant research  Network management and control Need for efficiency and aggregation in limited-capacity mobile networks  Mobile node health and status monitoring - Preemptive maintenance - Get it “back to the barn” for repairs


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