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TCP/IP Over LEO Satellites

TCP/IP Over LEO Satellites. Related Activities within the ATM-Sat Project Presentation to Industry Representatives and Interested Scientists. Contents. Test- & Measurement Suite Global Set-Up Probe Station Simulation Environment First Simulation Results. Satellite. Channel Emulation.

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TCP/IP Over LEO Satellites

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  1. TCP/IP Over LEO Satellites Related Activities within the ATM-Sat Project Presentation to Industry Representatives and Interested Scientists Marc Emmelmann

  2. Contents • Test- & Measurement Suite • Global Set-Up • Probe Station • Simulation Environment • First Simulation Results Marc Emmelmann

  3. Satellite Channel Emulation Satellite Modem Satellite Modem ATM-Sat Demonstrator Hardware Global Set-Up Probe Station Probe Station Marc Emmelmann

  4. Probe Station • Consists of: • Workstation or PC running standard operating system • FreeBSD • Windows • further OS possible • Protocol & performance testing tools (RFC 2398) • Used as: • TCP analyzer • User application platform Marc Emmelmann

  5. TCP Analyzer • Fundamental Performance Evaluation • Pre-defined set of experiments • Automatic execution • Base for comparing TCP flavors and network effects • Configuration: • Operation System: FreeBSD 4.1 • Testing Tools: DBS, netperf, ... Marc Emmelmann

  6. User Application Platform • Subjective QoS • Set of “daily life” applications • User interaction • Supplementary performance evaluation • Configuration: • Operation System: Windows, Unix, ... • Applications: Web-Browsing, NFS, etc. • Supplementary Tools: tcptrace, tcpdump, ... Marc Emmelmann

  7. Where We Are ... • Test- & Measurement Suite  • Simulation Environment • General Aspects • System Parameter • First Simulation Results Marc Emmelmann

  8. General Aspects • Independence of demonstrator hardware • Availabiltity only within final phase • Isolate demonstrator (hardware) specifc side effects • Unknown flavors of TCP • Analysis of “large” networks • Adaptation to emerging project constrains • Simulation tool: OPNET modeler / radio • Industry prooven • ATM support • Satellite Orbits can be included • Project specific aspects Marc Emmelmann

  9. System Parameters • Satellite Orbit • Bit Rates • Bit Error Rate • Up- & Down-Link Delay • Intra-Satellite Delay • End-to-End Delay Marc Emmelmann

  10. Satellite Orbit • Slant Range • Analytical model • Function of orbit altitude • Visibility constrains • Analytical vs. Simulated Distance • STK based simulation compared to theroy • derivation less than 2% Marc Emmelmann

  11. Service Uplink (fixed):2.048 Mbit/s Service Uplink (portable):384 kbit/s Bit Rates ISL: 7 - 10 Gbit/s Feeder Up & Downlink:32.768 Mbit/s Service Downlink:32.768 Mbit/s Marc Emmelmann

  12. Bit Error Rate • BER at target system above MAC • Up- & Down-Link • Good weather condition: 2*10E-8 • Rain • causes link to collaps • last for approx. 10 minutes • “on-off” modell • ISLs • Limitations Marc Emmelmann

  13. Up- & Down-Link Delay • Based upon analytically gained distance • Comparison analytical vs. simulated delay Marc Emmelmann

  14. Intra-Satellite Delay • Final “routes in the sky” still open • Assumed ISLs: • To forward and backward satellite • To left and right neighbor • Simulation based delays Marc Emmelmann

  15. End-to-End Delay • Describes aspects of: • Routing behavior “in the sky” • Intercontinental connections • Cooperate networks • Currently not considered • Obtained through final simulations • Reference measurements predict approx 150ms Marc Emmelmann

  16. Where We Are ... • Test- & Measurement Suite  • Simulation Environment  • First Simulation Results • Link Model Description • Link Model Verification • RTT Measurement of TCP • Future Steps Marc Emmelmann

  17. Link Model Description • Link: • Point-to-point • Symmetrical or asymmetrical • Wired • Delay • Function of time • Deterministic, periodical • Configurable Parameter: • BER • Bit rate Marc Emmelmann

  18. Link Model Verification • Delay: • Expected values • Consider queuing delay • Bit rate • Upper Limit Marc Emmelmann

  19. RTT Measurement of TCP • Impact of RTT-gain coefficient • Acts as „smoothing“ factor • Considered values • gain = 0.125 • gain = 1 • Results • Derivation less than 1ms • „Smoothed“ curved closerto real round-trip delayvariation Marc Emmelmann

  20. Future Steps • Timer granularity • Effects of variable delay on throughput • Switch to wireless link model • Better BER model • Simulation of “large” networks • Include ATM-Sat MAC Marc Emmelmann

  21. World Wide Web • http://www.fokus.gmd.de • Information about FOKUS • http://www.fokus.gmd.de/cats • Information about the Competence Center CATS • http://www.fokus.gmd.de/cats/projects • Information about the project • http://www.fokus.gmd.de/cats/publ • Download this presentation • Other CATS publications Marc Emmelmann

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