Handbook for Using IP Protocols for Space Missions

1. Handbook for Using IP Protocols for Space Missions James Rash - NASA/GSFC Keith Hogie, Ed Criscuolo, Ralph Casasanta - Computer Sciences Corp SIW-4 - IP in Space Implementation Guide

2. Background • GSFC OMNI Project started doing “Space Internet” demos in 1999 • TDRSS demos - demonstrating audio, video, data over TDRSS links • UoSAT-12 - full IP connectivity to an orbiting spacecraft • CHIPSat - mission designed using results from UoSAT-12 tests • CANDOS - IP experiments on STS-107 shuttle flight • Information was collected on performance aspects of standard Internet protocols • Many lessons were learned from these demonstrations • Work was initiated in 2002 to start organizing information for distribution to anyone else interested in using IP in space • First draft was prepared in Sept. 2003 and began circulating for review • Release of version 1 set for June 2004 • Plan is to continue adding information as issues such as security become better defined SIW-4 - IP in Space Implementation Guide

3. Document Contents • Overview • Lessons Learned • Architecture • Operational Scenarios • Security • Appendices • IP Tutorial • Space-to-Ground Link Layer Protocol • IP Performance Analysis • UDP-based Reliable File Transfer Protocols • TCP/IP Characteristics and Limitations • Request For Comment (RFC) References SIW-4 - IP in Space Implementation Guide

4. Lessons Learned • Review of current uses of IP in space • UoSAT-12 • AlSAT-1 • CHIPSat • CANDOS • BILSAT, NigeriaSat-1, UK-DMC • Summary of lessons learned across all missions • Data Link • Network Protocols • Transport Protocols • Applications • Test and Analysis Tools • This section covers overall experiences and doesn’t go into low level technical details SIW-4 - IP in Space Implementation Guide

5. Architecture • Architecture Trades • List of issues and alternatives • Simple IP spacecraft ( one IP address) • More Complex IP spacecraft (LAN onboard) • Components needed and current availability • Onboard, space-to-ground, ground • Ground system issues • Ground stations, control centers, data processing facilities SIW-4 - IP in Space Implementation Guide

6. Operational Scenarios • This section discusses various IP transport and application protocols and their applicable space communication scenarios • Major topics include using UDP and TCP for: • Commanding • Real-time telemetry • Stored data delivery (file transfer) • Network based time synchronization SIW-4 - IP in Space Implementation Guide

7. Security • This section primarily references other NASA documents on mission security • It lists key issues that have been identified by NASA network security groups for operational usage of IP • It does not list detailed security solutions since they are still being worked on by various NASA groups • Goal is to leverage security solutions from the commercial Internet world • Result will be some combination of current physical security and network isolation with more proactive security mechanisms to provide higher security and enable new connectivity options • More details will be added to the document as they are worked out SIW-4 - IP in Space Implementation Guide

8. Appendix A - Protocol Layering • This section provides basic reference information for Internet protocols • A review of the basic communication layers and their functions • A brief overview of the Mobile IP protocol and how it can be used to support automated routing for space missions • Data formats for basic Internet protocols: • IP • UDP • RTP • TCP • Discussion of the Network Time Protocol (NTP) • Discussion of Quality of Service issues related to space links SIW-4 - IP in Space Implementation Guide

9. Appendix B - Space-to-ground Data Link Protocols • Summary of CCSDS link layer protocols • Summary of HDLC framing • Discussion of how HDLC framing could be integrated with the CCSDS recommendations SIW-4 - IP in Space Implementation Guide

10. Appendix C - IP Performance Analysis • Comparison information on CCSDS and IP protocol overhead • Diagrams of CCSDS and IP (TCP and UDP) frame formats • Plot of protocol overhead comparison SIW-4 - IP in Space Implementation Guide

11. Appendix D - UDP Based Reliable File Transfer • This section provides a brief discussion of various options for performing reliable file transfers using UDP/IP protocols • UDP/IP is well suited to space link use since there is no “state” maintained at the transport layer • UDP/IP allows the end applications to decide how they want to handle issues such as link outage, long propagation delay, and errors • The UDP-based file transfer protocols discussed are: • CFDP - CCSDS File Delivery Protocol • MDP - Multicast File Delivery Protocol • NORM - NACK Oriented Reliable Multicast • Digital Fountain - Meta-content mechanisms SIW-4 - IP in Space Implementation Guide

12. Appendix E - TCP/IP Characteristics and Limitations • This section contains some basic information on TCP window size and link asymmetry issues • Reference table of data transfer rates and minimum TCP window sizes for orbits in LEO, MEO, GEO, and Mars • Discussion of TCP throughput, link asymmetry, and packet size SIW-4 - IP in Space Implementation Guide

13. Future Work • The document is intended to be a “living document” that will be continually updated with new and additional information. • Some of the primary areas for updates are: • Security policies and solutions • Mission lessons learned from new missions • More operational scenarios • More file transfer details • Any inputs are welcome on topics to be included • Send any inputs and comments to: • James.L.Rash@nasa.gov • The current version of the document will be available on the OMNI project web site: • http://ipinspace.gsfc.nasa.gov/documents/IPHandBook.pdf SIW-4 - IP in Space Implementation Guide