June 2004 SIW-4 - IP in Space Implementation Guide 1 Handbook for Using IP Protocols for Space Missions James Rash - NASA/GSFC Keith Hogie, Ed Criscuolo, Ralph Casasanta - Computer Sciences Corp

June 2004 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 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

June 2004 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

June 2004 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

June 2004 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

June 2004 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

June 2004 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

June 2004 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

June 2004 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

June 2004 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

June 2004 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

June 2004 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

June 2004 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: The current version of the document will be available on the OMNI project web site: –