CCSDS Fall 2009 Meeting ESTEC 28/10/2009

1. Progress Report on ESA/ESOC DTN Testbed V. Tsaoussidis, DUTH – Greece CCSDS Fall 2009 Meeting ESTEC 28/10/2009

2. ESA DTN Testbed Departing Question: What are the driving needs for DTN?  No, not just interoperability Fundamental Issues: Does it work? Can it work for Space? (Where) Is it functionally richer than CFDP, for example? Is it efficient enough, performance-wise? Can we quantify the gain from the use of DTN? DTN should not just work, but work where others fail. – By Definition. Evaluate it in stressed environments – search every aspect of it. CCSDS Fall 2009 Meeting 2/13

3. When we say search, we mean search.

4. Design a testbed for • Dynamic control of network parameters • Emulation of fundamental network parameters (bandwidth, PER, connectivity availability) • Realistic and dynamic adaptation to parameter changes in real-time (packet loss rate emulating solar storms, etc.) • Scalability • Efficient scaling over a large number of communication nodes • Transparency • Network emulation should be transparent to upper layer protocols and applications • Flexibility • Emulation of any desirable communication topology • Incorporation of new protocols, architectures, mechanisms • Interoperability with other DTN testbeds • Reusable infrastructure CCSDS Fall 2009 Meeting 3/13

5. Architecture CCSDS Fall 2009 Meeting 4/13

6. Architecture: Administrative Part • Graphical User Interface • Input of experiment parameters regarding: • Nodes (number, data production – consumption, storage size) • Links (bandwidth, error rate, propagation delay, availability) • Available protocols • Modification of parameters while the experiment is on progress • Real-time presentation of testbed statistics and status information • Kinematics Modeling System • Creation of the communication scenarios • Creation of the corresponding control data for the nodes • Central Management System • Handling of the communication between the various testbed components • Exchange of control data and status reports with the Emulation Nodes CCSDS Fall 2009 Meeting 5/13

7. Architecture: Emulation Part • Emulation Nodes • Control Daemon • sets node parameters • generates status reports • communicates with Central Management System through the Control Plane • Node Protocol Stack • Protocol stack under evaluation • Individual PCs communicate through the Data plane, exchanging files • such as images, measurements, etc. CCSDS Fall 2009 Meeting 6/13

8. Testbed Topology • Ten Emulation Nodes • Suitable for complex space communication scenarios • Intercontinental Link with MIT - Boston • Suitable for terrestrial scenarios • Geostationary Link (HellasSat Geo Satellite) • Suitable for low-orbit scenarios CCSDS Fall 2009 Meeting 7/13

9. Protocol Stack • DTN Implementation: Interplanetary Overlay Network (ION) • Bundle Protocol • Asynchronous Message Service (AMS) • Licklider Transmission Protocol (LTP) • Contact Graph Routing (CGR) • Interoperates with DTN2 • An advanced application layer protocol is • required (e.g. CFDP) • CCSDS File Delivery Protocol (CFDP) • Automatic, reliable file transfer • File segmentation • Remote file management and directory listing • Lacks dynamic routing support CCSDS Fall 2009 Meeting 8/13

10. Complicated Scenario CCSDS Fall 2009 Meeting 9/13

11. Progress so far • Integration of CFDP into ION protocol stack • Performance evaluation of CFDP over ION versus CFDP as a stand alone application • Integration of CCSDS Space Packet protocol • Implementation of the protocol’s basic functionality • Evaluation of several DTN routing protocols • Comparison of Contact Graph Routing (CGR) with Probabilistic Routing Protocol using a History of Encounters and Transitivity (PRoPHET) and Flood routing • Design of efficient space oriented DTN transport • protocols • DS-TP • DTTP CCSDS Fall 2009 Meeting 10/13

12. Progress so far • Integration of CFDP into ION protocol stack • Objective: Exploit CFDP file management features • CFDP on endpoints in unacknowledged mode • All intermediate nodes run ION • Reliability is achieved by the underlying network (BP, LTP) • Integration: • Middleware Application • Receives CFDP PDUs • Each CFPD PDU is encapsulated into a bundle • Requires mapping between CFDP ID and DTN EID • Validation – Evaluation: CFDP over BP/TCP and CFDP over BP/LTP CCSDS Fall 2009 Meeting 10/13

13. Progress so far • Integration of CCSDS Space Packet Protocol into ION • Objective: Deployment of an architecture possibly used by ESA in future DTN space communications • Basic implementation of the Space Packet Protocol below LTP • Each LTP segment is encapsulated into a Space Packet • LTP Engine Number to APID mapping • Independent Packet Sequence Count for each LTP span • Intermediate nodes supporting only the Space Packet Protocol • Static routing of space packets based on APID between non-DTN nodes CCSDS Fall 2009 Meeting 10/13

14. Progress so far • Evaluation of several DTN routing protocols • Objective: Comparison of Contact Graph Routing (CGR) with Probabilistic Routing Protocol using a History of Encounters and Transitivity (PRoPHET) and Flood routing • Observations • CGR outperforms both PRoPHET and Flood Routing when delay is in the order of seconds • PRoPHET does not perform well even for short delay values • CGR needs to have predetermined contact plans in order to operate and cannot cope with opportunistic contacts CCSDS Fall 2009 Meeting 10/13

15. Work-in-Progress • Evaluation of Fragmentation and Bundle-size performance • Design and implementation of an efficient DTN routing • scheme, using parameters such as • Resource availability • Custody requirements • Foreign agency assets exploitation • Implementation of an advanced Kinematics module • Dynamic adjustment of link characteristics, based on real planet and satellite trajectories, random solar storms etc. CCSDS Fall 2009 Meeting 11/13

16. Suggestion Test functionality – prove it is operational Test efficiency – custody, fragmentation, routing Test efficiency – when others fail.