International Workshop on Satellite and Space Communications 2009, IWSSC 2009, 9-11 September 2009, Siena, Italy 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 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 – 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 2 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

What gap does this work fill in During the last decade CCSDS has developed CFDP as a file transfer protocol for space communications – 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? 3 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

4 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

Protocols with cross-layer funcionality Space Packet Protocol – is really an application layer artifact – has a simple naming mechanism (APID) – static routing through LDPs CCSDS File Delivery Protocol – has transport layer functionalities as well – supports store-and-forward 5 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

CCSDS File Delivery Protocol 1/2 Application Layer Protocol for file transferring Transport Layer Functionalities – Two modes of operation (unacknowledged / acknowledged mode) – Three file delivery services (Core / Extended Procedures / SFO) – Four ACK modes (Deferred / Immediate / Prompted / Asynchronous 6 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

CCSDS File Delivery Protocol 2/2 CFDP is unsuitable when communication complexity increases – No dynamic routing – No file distribution through multiple relay points in parallel – No advanced retransmission mechanisms – No end-to-end security 7 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

Towards Delay Tolerant Networking New protocols and mechanisms for routing and transfer reliability are needed in order to deal with: – Alternative communication paths – Intermittent connectivity – Large propagation delays – High BER – Resource sharing among space agencies DTN Architecture tends to dominate the field 8 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

DTN Architecture Store and Forward message switching Custody Transfer Reliability of lower layer (LTP, DS-TP, etc) Proactive and Reactive Fragmentation Flexible naming scheme with Late Binding Dynamic Routing 9 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

DTN Architecture 10 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

The problem Space agencies will continue to use current infrastructure – legacy mission support – financial reasons Questions: – How CFDP cooperates with DTN? – Is there any functionality overlapping? – How it performs? 11 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

CFDP and DTN comparison FeaturesCFDPDTN File managementYesNo ReliabilityYes SFOYes Custody TransferYes*Yes Global namingNoYes RoutingNoYes SecurityNoYes 12 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy Solution: keep all the file management features and disable all other

Evaluation scenario 13 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy COMNET lab’s space oriented communication Testbed CFDP over DTN (ION) – Each CFDP PDU is encapsulated in a “bundle” – CFDP at the endpoints Simple 2-node topology 1Kbyte CFDP PDU size – Data aggregation/segmentation is left to the underlying network

COMNET lab’s Testbed 1/2 14 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

COMNET lab’s Testbed 2/2 Distributed nodes – COMNET Lab, DUTH, Xanthi, Greece – Hellenic Aerospace Industry, Athens, Greece – Massachusetts Institute of Technology, USA Protocols Implemented: – ESA/ESTEC CFDP implementation – 2 Bundle Protocol Implementations (ION and DTN2) – LTP – CCSDS Space Packet Protocol (soon) 15 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

Terrestrial and Geostationary links CFDP/BP/TCP 10 MByte file size 1 Mbps/ 256 Kbps ms propagation delay 0 – 10% PER 16 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

Deep-space links CFDP/BP/LTP and CFDP/UDP 5 and10 MByte file size 1 Mbps/ 256 Kbps 30 sec propagation delay 0 – 10% PER 17 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

Conclusions It is feasible to operate CFDP only as a file application protocol over DTN (ION) Advantages of such integration could be : – 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, DS- TP) Further results are still needed to identify potential trade- offs and the mechanisms required to maximize performance 18 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy

Thank you Any questions? 19 International Workshop on Satellite and Space Communications 2008, IWSSC 2009, September 2009, Siena, Italy

References ComNet Group: ESA Project Site: rt.gr/Projects/ExtendingInternet IntoSpace/ home.aspxhttp:// 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."Extending Internet into Space – ESA DTN Testbed Implementation and Evaluation", 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, "Deep-Space Transport Protocol: A Novel Transport Scheme for Space DTNs" 20 International Workshop on Satellite and Space Communications 2009, IWSSC 2009, September 2009, Siena, Italy