A flexible interplanetary Internet

1. A flexible interplanetary Internet Stephen Farrell Trinity College Dublin, Ireland Stephen.Farrell@cs.tcd.ie Christian Jensen Technical University of Denmark

2. Background • Work on Interplanetary Internet (IPN) • “Bundles” passed between nodes during strictly scheduled “contacts” • ISOC SIG: http://www.ipnsig.org • Generalised as a study of Delay tolerant networking (DTN) • E.g. Sensor networks, some application based on 1980's email • IRTF RG: http://www.dtnrg.org • DTN vs IPN • Generally not (very) strictly scheduled • Less predictable data flows • Broader applicability

3. Reasons to look at this • More direct PI control of experiments • Network (more) ignorant of application • More flexible experiment communications • Constellations, Sensor networks, weather etc. • Data from new SC using old SC as routers • Ubiquitous network stack including forwarding • Ability to handle more S/C • Alleviate DSN bottleneck, improve re-scheduling • Longer mission duration (SEP)

4. A (Comp. Sci.) reason to look at this • Internet architecture calls for all (well, most) intelligence to be at the network edges • Drop packets if you must • Eases new service introduction (ISPs don't care) • Web architecture calls for accepting (as normal) unresolved links • Databases no longer require link integrity and are much easier to start • Can an IPN take a similar approach? • Would it be better if it did? • Maybe, but depends on the “scale” of the network

5. When scaling might hit... • DSN oversubscription • Probably always inevitable • Inherently “bursty” experiments • Perhaps space weather, GRBs (and other things I don't understand:-) • New SC comms architectures • Orbiter, primary lander, secondary sensor nodes each with different comms. capabilities • Humans beyond LEO

6. “Flexible” IPN concept • Its a DTN which • Meets IPN requirements to handle latency, uni-directional comms etc. • Includes schedule generation and distribution (in a delay-tolerant fashion!) • Allows simultaneous use of various routing topologies and forwarding schemes • Aiming to • Allow PIs to control their experiments from their desktops to a much greater degree than today • Increase the efficiency of the overall use of resources, when hit by scale factors

7. Flexible IPN example • PI has sensors deployed from a lander • Sensors have settings which determine when they produce data • PI decides to change settings • Commands (eventually) get to sensors via orbiter(s) and lander • Orbiters may use a token ring equivalent • Lander/sensors may use (a successor to) AODV • PI need not/cannot determine exactly when commands executed • (Some time later) Data from sensors increases • Routers (eventually) notice this and reschedule • Routers in sensors, lander, orbiter(s), earthstation • Schedule subject to many constraints (e.g. overall lander data budget), maybe centrally generated

8. So far... • Simulations • Based on OMNET++ discrete event simulator and JPL DE406 ephemeris (and maybe cspice if necessary) • Routing topologies and forwarding schemes • Concept of the schedule as a data structure that is also distributed • Similar to how train timetables worked before telegraph • Some work on schedule visualisation • Traffic patterns • Request/response pattern • Triggered sensor pattern

9. Planned... • Incorporate the scheduling and routing schemes into hardware • Lake water quality monitoring sensor network application • H/W prototype planned for Spring '04 • Continue work on the “flexible” IPN concept and related simulations • Improve models (visibility, power, re-scheduling) • Would like to get good data against which to compare the simulations!

10. Tentative conclusions • Arguments for flexible IPN seem to be relatively convincing • Scaling and unpredictable traffic patterns => congestion handling and all that goes with that • Initial simulation results may support these arguments • Very early days here • Maybe layering violations are good! • When calculating schedules anyway, adding in the LTT's involved might help an edge node to re-calculate its scheduling without knowing much about the ephemeris

11. Questions?Now, later, or tostephen.farrell@cs.tcd.ieMore materials near:http://down.dsg.cs.tcd.ie/(will include a link to latest stuff when the paper's due)

17. ./flexi20031024-1/endrun.txt theIPN.sinks[0] bps is: 0.57013 (total bits: 1.46619e+06, total time: 2.592e+06) theIPN.sinks[0] reporting: DIM'd 38715 messages! theIPN.sinks[1] bps is: 814.86 (total bits: 2.10884e+09, total time: 2.592e+06) theIPN.sinks[2] bps is: 121.361 (total bits: 3.14555e+08, total time: 2.592e+06) ./hand20031024-1/endrun.txt theIPN.sinks[0] bps is: 17.8894 (total bits: 4.63059e+07, total time: 2.592e+06) theIPN.sinks[0] reporting: DIM'd 8087 messages! theIPN.sinks[1] bps is: 164.394 (total bits: 4.25888e+08, total time: 2.592e+06) theIPN.sinks[2] bps is: 150.411 (total bits: 3.89862e+08, total time: 2.592e+06) ./hand20031024-2/endrun.txt theIPN.sinks[0] bps is: 151.734 (total bits: 3.92843e+08, total time: 2.592e+06) theIPN.sinks[0] reporting: DIM'd 16661 messages! theIPN.sinks[1] bps is: 1503.07 (total bits: 3.89393e+09, total time: 2.592e+06) theIPN.sinks[2] bps is: 139.669 (total bits: 3.62021e+08, total time: 2.592e+06) ./flexi20031024-2/endrun.txt theIPN.sinks[0] bps is: 117.274 (total bits: 3.03969e+08, total time: 2.592e+06) theIPN.sinks[0] reporting: DIM'd 42463 messages! theIPN.sinks[1] bps is: 1823.34 (total bits: 4.726e+09, total time: 2.592e+06) theIPN.sinks[2] bps is: 116.137 (total bits: 3.0102e+08, total time: 2.592e+06) ./filled20031030-1/endrun.txt theIPN.sinks[0] bps is: 191.537 (total bits: 4.96459e+08, total time: 2.592e+06) theIPN.sinks[0] reporting: DIM'd 15037 messages! theIPN.sinks[1] bps is: 1831.17 (total bits: 4.74637e+09, total time: 2.592e+06) theIPN.sinks[2] bps is: 288.596 (total bits: 7.48032e+08, total time: 2.592e+06)