Transcript Planes, Trains and DTN - Applied Physics Laboratory

Planes, Trains and DTN
(Delay Tolerant Networking)
Ashton G. Vaughs
Jet Propulsion Laboratory
Copyright 2009 California Institute of Technology
Government Sponsorship Acknowledged
Release Number: CL#09-4540
November 4-6, 2009
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Transportation Networks
ORD
Los Angeles
DIA
JFK
Norwalk
Anaheim
LAX
San Juan C.
BEGIN
Transfer
San Diego
Items transported:
•People
•Freight
END
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Travel Example
Point
A
Point
B
LAX to DIA
Point
A’
Layover
#1
Point
B’
DIA to ORD
DIA
Point
A’’
Layover
#2
Point
B’’
ORD to JFK
ORD
The Traveler remains in the
custody of DIA and ORD airports
during Layovers.
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Relevant Travel Issues
• Time Tables
Transportation Networks
– Starting Location (A)
– Departure Time
– Arrival Time
– Ending Location (B)
• Derived Information
– Transit Time (Trip Duration)
– Layover Time
– Distance remaining to Final Destination
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Communications Network
Planet
“Obstruction”
Items transported:
•Bits
•Information
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Communication Example
Data Arrives at Receiver
OWLT
Sender
Receiver
Transmit Data
OWLT
Begin Transmission
End Transmission
time
twindow opens
twindow closes
OWLT = One Way Light Time
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Relevant Travel Issues
• Time Tables
Communications Networks
– Sender Location (A)
– One Way Light Time
– Transmission Window Duration
– Receiver Location (B)
• Derived Information
– Transmission Duration
– Custody Duration
– Distance remaining to Final Destination
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The Connection
DTN enables the representation
of complex technical data with a
simple and intuitive model.
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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
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Possibilities are Limitless
Earth
•DSN Stations
•Titan Polar Orbiter
•Saturn Moonlet Rider
•Titan Submarine
Titan
Saturn
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Possibilities are Limitless
Earth
•DSN Stations
•Titan Polar Orbiter
•Saturn Moonlet Rider
•Titan Submarine
Titan
Saturn
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Backup Slides
Planes, Trains and DTN
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DTN Disconnectathon
July 29, 30 and 31 2009
Stockholm / North America
Will Ivancic
[email protected]
216-433-3494
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Ohio University Disconnectathon Testbed
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Trinity College Dublin Disconnectathon Testbed
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First Look at the Deep Impact
DTN Experiment (DINET)
Scott Burleigh
Jet Propulsion Laboratory
California Institute of Technology
Copyright 2008 California Institute of Technology
Government sponsorship acknowledged.
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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.
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The DINET Stack
image publisher/receiver
AMS
messaging
load/go utility
for network administration
Remote AMS
compression
BP forwarding
Convergence layer adapter
LTP retransmission
Link service adapter
admin
programs,
rfx system,
clocks
CCSDS space
packets
CCSDS TM/TC
X-band R/F
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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.
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