CCSDS Fall 2009 Meeting ESTEC 28/10/2009

Progress Report on

ESA/ESOC DTN Testbed

V. Tsaoussidis, DUTH – Greece

ESA DTN Testbed

CCSDS Fall 2009 Meeting 2/13

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?

Departing Question:What are the driving needs for DTN?

No, not just interoperability

DTN should not just work, but work where others fail. – By Definition.Evaluate it in stressed environments – search every aspect of it.

When we say search, we mean search.

3

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

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Architecture

CCSDS Fall 2009 Meeting 4/13

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

Architecture: Emulation Part

Emulation Nodes• Control Daemon

sets node parametersgenerates status reportscommunicates with Central Management System through the Control Plane

• Node Protocol StackProtocol stack under evaluation

CCSDS Fall 2009 Meeting

Individual PCs communicate through the Data plane, exchanging files such as images, measurements, etc.

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Testbed Topology

CCSDS Fall 2009 Meeting

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

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Protocol Stack

CCSDS Fall 2009 Meeting

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

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Complicated Scenario

CCSDS Fall 2009 Meeting 9/13

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

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

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

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

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

Suggestion

16

Test functionality – prove it is operational

Test efficiency – custody, fragmentation, routing

Test efficiency – when others fail.