Transcript Space IP Handbook

Handbook for Using IP
Protocols for Space Missions
James Rash
- NASA/GSFC
NASDA
Keith Hogie, Ed Criscuolo,
Ralph Casasanta
- Computer Sciences
Corp
Inst. A
Inst. B
(IP addr)
(IP addr)
C&DH
Router
Ground Stations
(IP addr)
Multiple Address
Spacecraft
RF
IP in
HDLC
frames
RF Equip
Data
Services
(File &)
(Packet)
Space IP
Routing
Internet
Collaborative
Investigator
Ground IP
Routing
Legacy Systems
Dial-up
Scientist
ESA
Security Firewall
C&DH
(IP addr)
RF
Single Address
Spacecraft
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Principal
Investigator
Private IP
Network
Control Center/
Data Distribution Facility
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Background
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GSFC OMNI Project started doing “Space Internet” demos in 1999
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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
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Information was collected on performance aspects of standard
Internet protocols
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Many lessons were learned from these demonstrations
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Work was initiated in 2002 to start organizing information for
distribution to anyone else interested in using IP in space
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First draft was prepared in Sept. 2003 and began circulating for
review
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Release of version 1 set for June 2004
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Plan is to continue adding information as issues such as security
become better defined
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Document Contents
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Overview
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Lessons Learned
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Architecture
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Operational Scenarios
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Security
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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
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Lessons Learned
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Review of current uses of IP in space
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Summary of lessons learned across all missions
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UoSAT-12
AlSAT-1
CHIPSat
CANDOS
BILSAT, NigeriaSat-1, UK-DMC
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
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Architecture
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Architecture Trades
– List of issues and alternatives
– Simple IP spacecraft ( one IP address)
– More Complex IP spacecraft (LAN onboard)
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Components needed and current availability
– Onboard, space-to-ground, ground
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Ground system issues
– Ground stations, control centers, data processing facilities
Subsystems
(power,
ACS)
Inst. A Mass
Store
Inst. B
Cmd & Data
Handling
Router/
Bridge
Transmitter/
Receiver
UDP
IP
IP
IP
IP
Ether
NIC
Ether
NIC
Ether
NIC
1553
NIC
IP
1553
NIC
Router
Time
Server
Mass
Store
IP
NTP
IP
IP
Ether
NIC
Ether
NIC
IP
Ether
NIC
Ether
NIC
HDLC
Network
Transmitter/
Receiver
Framing (e.g. HDLC, ATM, DVB)
HDLC
Ether
NIC
Encryption
Crypt
Ethernet Hub/Switch
Onboard LAN Hardware
Code
FEC coding (e.g. R/S, TPC, LDPC)
Crypt
Modulation (e.g. QPSK, 8PSK)
Code
Mod
RF/
Optic
Mod
RF/ Optical
Transmitter/Receiv er
Onboard WAN hardware
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Bit
Store
Ethernet Hub/Switch
Ground LAN Components
RF/
Optic
Ground WAN Components
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Operational Scenarios
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This section discusses various IP transport and application protocols
and their applicable space communication scenarios
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Major topics include using UDP and TCP for:
– Commanding
– Real-time telemetry
– Stored data delivery (file transfer)
– Network based time synchronization
Delay Se ns itive
Delay Tolerant
HTTP
FTP
5/6/7 - Application
NTP
SMTP
Audio
Video
MDP
RTP
TCP
4 - Transport
UDP
IPse c (AH/ESP)
IP
3 - Network
2 - Data Link
1355
1394
Ethernet
ATM
POS
HDLC
SONET
1 - Physical
Copper
Fiber
RF
Fiber
Copper
RF
Space
Spe cific
Link
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Security
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This section primarily references other NASA documents on
mission security
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It lists key issues that have been identified by NASA network
security groups for operational usage of IP
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It does not list detailed security solutions since they are still being
worked on by various NASA groups
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Goal is to leverage security solutions from the commercial Internet
world
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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
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More details will be added to the document as they are worked out
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Appendix A - Protocol Layering
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This section provides basic reference information for Internet
protocols
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A review of the basic communication layers and their functions
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A brief overview of the Mobile IP protocol and how it can be used
to support automated routing for space missions
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Data formats for basic Internet protocols:
– IP
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4-bit
v ers
4-bit
hdr len
– UDP
31
16-bit total length (in bytes)
0 D M
F F
16-bit identification
8-bit time to
Liv e (TTL)
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8-bit type of
serv ice (TOS)
8-bit protocol
13-bit fragment offset
16-bit header checksum
32-bit source IP address
32-bit destination IP address
– RTP
Options (if any)
– TCP
Data
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Discussion of the Network Time Protocol (NTP)
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Discussion of Quality of Service issues related to space links
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Appendix B - Space-to-ground Data Link Protocols
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Summary of CCSDS link layer protocols
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Summary of HDLC framing
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Discussion of how HDLC framing could be integrated with the
CCSDS recommendations
Trans fer Frame
VC
Frame Re lay Frame
Pack ets , Bits , e tc.
C
R
C
F
L
G
Space Data Link
Protocols
Transfer Frames
Sync and Channel
Coding
Pack ets , Bits , e tc.
HDLC Frame
C F
R L
CG
Bits or Bytes
R/S Code block
Sy nc
Mark
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DL
CI
Data
R/S
sy mbols
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Appendix C - IP Performance Analysis
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Comparison information on CCSDS and IP protocol overhead
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Diagrams of CCSDS and IP (TCP and UDP) frame formats
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Plot of protocol overhead comparison
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Appendix D - UDP Based Reliable File Transfer
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This section provides a brief discussion of various options for
performing reliable file transfers using UDP/IP protocols
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UDP/IP is well suited to space link use since there is no “state”
maintained at the transport layer
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UDP/IP allows the end applications to decide how they want to
handle issues such as link outage, long propagation delay, and
errors
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The UDP-based file transfer protocols discussed are:
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CFDP - CCSDS File Delivery Protocol
MDP - Multicast File Delivery Protocol
NORM - NACK Oriented Reliable Multicast
Digital Fountain - Meta-content mechanisms
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Appendix E - TCP/IP Characteristics and Limitations
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This section contains some basic information on TCP window size
and link asymmetry issues
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Reference table of data transfer rates and minimum TCP window
sizes for orbits in LEO, MEO, GEO, and Mars
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Discussion of TCP throughput, link asymmetry, and packet size
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Future Work
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The document is intended to be a “living document” that will be
continually updated with new and additional information.
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Some of the primary areas for updates are:
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Security policies and solutions
Mission lessons learned from new missions
More operational scenarios
More file transfer details
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Any inputs are welcome on topics to be included
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Send any inputs and comments to:
– [email protected]
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The current version of the document will be available on the OMNI
project web site:
– http://ipinspace.gsfc.nasa.gov/documents/IPHandBook.pdf
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