Transcript slides - InterSys Lab

Evaluation of CCSDS File Delivery Protocol
over Delay Tolerant Networks
Giorgos Papastergiou,
Hellenic Aerospace Industry S.A, Schimatari,
Greece
Democritus University of Thrace , Xanthi, Greece
E. Koutsogiannis and V. Tsaoussidis
International Workshop on Satellite and Space
Communications 2009, IWSSC 2009, 9-11
September 2009, Siena, Italy
Department of Electrical and Computer
Engineering, Democritus University of Thrace,
Xanthi, Greece
Work summary
Investigation of how CFDP can serve as the file
transfer protocol within the DTN architecture
Initial evaluation of its performance
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integration of ESA/ESTEC CFDP with JPL ION DTN
implementation
Evaluation using a space-oriented Testbed
Conclusion: CFDP can rely on DTN for naming,
routing, SFO and reliability
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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What gap does this work fill in
During the last decade CCSDS has developed CFDP
as a file transfer protocol for space communications
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CFDP is a ready-to-flight product
Future missions will support it
CFDP relies on current space infrastructure (SPP, TM/TC,
AOS)
DTN will be the future communication architecture
When migrating to DTN how can we take advantage of
the already developed CFDP protocol?
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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Current state
Increased number of space elements
need
for more automated and flexible communications
Current space communication protocols rely on
static routing,
–
while the number of alternative communication paths in
space increases
Space communication protocols have a rather cross-layer
functionality
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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Protocols with cross-layer
funcionality
Space Packet Protocol
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is really an application layer artifact
has a simple naming mechanism (APID)
static routing through LDPs
CCSDS File Delivery Protocol
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has transport layer functionalities as well
supports store-and-forward
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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CCSDS File Delivery Protocol 1/2

Application Layer Protocol for file transferring

Transport Layer Functionalities
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Two modes of operation (unacknowledged /
acknowledged mode)
Three file delivery services (Core / Extended
Procedures / SFO)
Four ACK modes (Deferred / Immediate / Prompted /
Asynchronous
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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CCSDS File Delivery Protocol 2/2
CFDP is unsuitable when communication complexity
increases
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No dynamic routing
No file distribution through multiple relay points in
parallel
No advanced retransmission mechanisms
No end-to-end security
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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Towards Delay Tolerant Networking
New protocols and mechanisms for routing and
transfer reliability are needed in order to deal with:
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Alternative communication paths
Intermittent connectivity
Large propagation delays
High BER
Resource sharing among space agencies
DTN Architecture tends to dominate the field
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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DTN Architecture

Store and Forward message switching

Custody Transfer

Reliability of lower layer (LTP, DS-TP, etc)

Proactive and Reactive Fragmentation
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Flexible naming scheme with Late Binding

Dynamic Routing
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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DTN Architecture
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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The problem
Space agencies will continue to use current
infrastructure
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legacy mission support
financial reasons
Questions:
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How CFDP cooperates with DTN?
Is there any functionality overlapping?
How it performs?
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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CFDP and DTN comparison
Features
CFDP
DTN
File management
Yes
No
Reliability
Yes
Yes
SFO
Yes
Yes
Custody Transfer
Yes*
Yes
Global naming
No
Yes
Routing
No
Yes
Security
No
Yes
Solution: keep all the file management features and
disable all other
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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Evaluation scenario


COMNET lab’s space oriented
communication Testbed
CFDP over DTN (ION)
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Each CFDP PDU is encapsulated in
a “bundle”
CFDP at the endpoints
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Simple 2-node topology
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1Kbyte CFDP PDU size
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Data aggregation/segmentation is
left to the underlying network
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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COMNET lab’s Testbed 1/2
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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COMNET lab’s Testbed 2/2
Distributed nodes
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COMNET Lab, DUTH, Xanthi, Greece
Hellenic Aerospace Industry, Athens, Greece
Massachusetts Institute of Technology, USA
Protocols Implemented:
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ESA/ESTEC CFDP implementation
2 Bundle Protocol Implementations (ION and DTN2)
LTP
CCSDS Space Packet Protocol (soon)
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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Terrestrial and Geostationary links

CFDP/BP/TCP
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10 MByte file size
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1 Mbps/ 256 Kbps
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50-300 ms
propagation delay
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0 – 10% PER
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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Deep-space links
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CFDP/BP/LTP and
CFDP/UDP
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5 and10 MByte file
size
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1 Mbps/ 256 Kbps

30 sec propagation
delay

0 – 10% PER
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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Conclusions

It is feasible to operate CFDP only as a file application
protocol over DTN (ION)
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Advantages of such integration could be :
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the exploitation of the advanced BP features (such as SFO, coarse
grained reliability, routing, naming, fragmentation)
the exploitation of the enhanced (re)transmission ability (LTP, DSTP)
Further results are still needed to identify potential tradeoffs and the mechanisms required to maximize
performance
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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Thank you

Any questions?
International Workshop on Satellite and Space Communications 2008, IWSSC 2009, 911 September 2009, Siena, Italy
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References
ComNet Group: http://comnet.ee.duth.gr
ESA Project Site: http://www.hai- rt.gr/Projects/ExtendingInternet IntoSpace/
home.aspx
ESA DTN Testbed: C. Samaras, I. Komnios, D. Sotirios, E. Koutsogiannis, V.
Tsaoussidis, G. Papastergiou and N. Peccia, "Extending Internet into Space –
ESA DTN Testbed Implementation and Evaluation", 1st International
Conference on Mobile Lightweight Wireless Systems, Workshop on Research
activities funded by ESA in Greece, Athens, Greece, May 18-20, 2009.
DS-TP: Giorgos Papastergiou, Ioannis Psaras and Vassilis Tsaoussidis
"Deep-Space Transport Protocol: A Novel Transport Scheme for Space DTNs"
Computer Communications (COMCOM), Elsevier Science, Special Issue on
Delay-/Disruption-Tolerant Networks, 2009.
International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 911 September 2009, Siena, Italy
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