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Planes, Trains and DTN(Delay Tolerant Networking)
Ashton G. VaughsJet Propulsion Laboratory
Copyright 2009 California Institute of TechnologyGovernment Sponsorship Acknowledged
Release Number: CL#09-4540
November 4-6, 2009 1AGV
Transportation Networks
LAX
DIA
ORD
JFK
Los Angeles
Norwalk
Anaheim
San Juan C.
San Diego
BEGIN
END
Transfer
Items transported:•People•Freight
Items transported:•People•Freight
November 4-6, 2009 2AGV
Travel Example
LAX to DIALAX to DIA Layover#1
Layover#1 DIA to ORDDIA to ORD Layover
#2Layover
#2 ORD to JFKORD to JFK
DIADIA ORDORD
The Traveler remains in the custody of DIA and ORD airports during Layovers.
The Traveler remains in the custody of DIA and ORD airports during Layovers.
PointA
PointA’
PointA’’
PointB
PointB’
PointB’’
November 4-6, 2009 3AGV
Relevant Travel Issues
• Time Tables– Starting Location (A)– Departure Time– Arrival Time– Ending Location (B)
• Derived Information– Transit Time (Trip Duration)– Layover Time– Distance remaining to Final Destination
Transportation NetworksTransportation Networks
November 4-6, 2009 4AGV
Communications Network
Planet“Obstruction”
Planet“Obstruction”
Items transported:•Bits•Information
Items transported:•Bits•Information
November 4-6, 2009 5AGV
Transmit DataTransmit Data
Communication Example
twindow opens twindow closes
Begin Transmission End Transmission
time
OWLT
OWLT
Sender Receiver
Data Arrives at Receiver
OWLT = One Way Light TimeOWLT = One Way Light Time
November 4-6, 2009 6AGV
Relevant Travel Issues
• Time Tables– Sender Location (A)– One Way Light Time– Transmission Window Duration– Receiver Location (B)
• Derived Information– Transmission Duration– Custody Duration– Distance remaining to Final Destination
Communications NetworksCommunications Networks
November 4-6, 2009 7AGV
The Connection
DTN enables the representation of complex technical data with a simple and intuitive model.
DTN enables the representation of complex technical data with a simple and intuitive model.
November 4-6, 2009 8AGV
DTN• Store and Forward system
– Layovers are analogous to Store (data remains in custody of the node)– Travel Time is analogous to Forwarding
• Multiple Transport Mechanisms– Planes, Trains and Buses– TCP, UDP, IP, R/F and LTP protocols*
• Flexible– Mesh– Tree– Star
• Efficient and Light Weight– Desktop Computers: DTN Disconnectathon– Spacecraft Computers: DINET
• Extensible– AMS– RAMS– CFDP
* List not exhaustive* List not exhaustive
November 4-6, 2009 9AGV
Possibilities are Limitless
TitanTitan
SaturnSaturn
Earth
•DSN Stations•Titan Polar Orbiter•Saturn Moonlet Rider•Titan Submarine
November 4-6, 2009 10AGV
Possibilities are Limitless
TitanTitan
SaturnSaturn
Earth
•DSN Stations•Titan Polar Orbiter•Saturn Moonlet Rider•Titan Submarine
November 4-6, 2009 11AGV
Backup Slides
Planes, Trains and DTN
November 4-6, 2009 12AGV
DTN DisconnectathonJuly 29, 30 and 31 2009
Stockholm / North America
Will Ivancic
216-433-3494
November 4-6, 2009 13AGV
Ohio University Disconnectathon Testbed
November 4-6, 2009 14AGV
Trinity College Dublin Disconnectathon Testbed
November 4-6, 2009 15AGV
November 4-6, 2009 SB-16
First Look at the Deep ImpactDTN Experiment (DINET)
Scott BurleighJet Propulsion Laboratory
California Institute of Technology
Copyright 2008 California Institute of TechnologyGovernment sponsorship acknowledged.
AGV
November 4-6, 2009 SB-17
DINET Summary• The purpose of the DINET project is to demonstrate NASA’s implementation of the
IRTF-conformant open Delay-Tolerant Networking protocols (Interplanetary Overlay Network – “ION”) in flight and ground software functioning at Technology Readiness Level 7 or 8, making it ready for use by space flight projects.
• Plan:– Upload ION software to the Deep Impact “flyby” spacecraft during inactive cruise
period, while the spacecraft is en route to encounter comet Hartley 2.– Use the DI (now “EPOXI”) spacecraft as a DTN router for image bundles flowing from
one lab machine to another, over interplanetary links.– Use the Deep Space Network tracking stations: eight tracking passes of 4 hours each,
separated by intervals of 2 to 5 days. Uplink at 250 bytes/sec, downlink at either 110 or 20,000 bytes/sec.
– On the last four passes, induce data loss by randomly discarding 1/32 of all received packets, thus forcing the exercise of LTP retransmission.
– One-way signal propagation delay is initially 81 seconds, drops to 49 seconds by the end of the four-week exercise.
– Use AMS publish/subscribe over BP/LTP to send about 300 small images through this network, via the spacecraft. Track statistics, display on reception.
AGV
November 4-6, 2009 SB-18
The DINET Stack
CCSDS TM/TC
X-band R/F
LTP retransmission
BP forwarding
CCSDS spacepackets
AMSmessaging
Remote AMScompression
Convergence layer adapter
Link service adapter
image publisher/receiver
load/go utilityfor network administration
adminprograms,rfx system,
clocks
AGV
November 4-6, 2009 SB-19
Key Findings
• The protocols work well.– Signal propagation delays of 49 to 89 seconds were tolerated.– End-to-end latencies on the order of days were tolerated.– Station handovers and transient failures in DSN uplink service were handled
automatically and invisibly.– Protocol overhead was minimal.– Dynamic route computation was generally successful.
• The software is highly stable.– No software failures in four weeks of continuous operation on VxWorks, Solaris, and
Linux platforms.– No effect on the operation of other flight software.– No leakage of memory or non-volatile storage space.
• Clock synchronization and OWLT estimation errors of several seconds had no noticeable effect on network operation.
AGV