1. Competence Center for Advanced Network Technologies and Systems http://www.fokus.gmd.de/cats http://www.fokus.gmd.de Marc Emmelmann TCP/IP Over LEO Satellites Related Activities within the ATM-Sat Project Presentation to Industry Representatives and Interested Scientists

2. 2000-12-12Marc Emmelmann2 Contents n Test- & Measurement Suite n Global Set-Up n Probe Station n Simulation Environment n First Simulation Results

3. 2000-12-12Marc Emmelmann3 Global Set-Up Probe Station Satellite Channel Emulation Satellite Modem Satellite Modem Probe Station ATM-Sat Demonstrator Hardware

4. 2000-12-12Marc Emmelmann4 Probe Station n Consists of: n Workstation or PC running standard operating system y FreeBSD y Windows y further OS possible n Protocol & performance testing tools (RFC 2398) n Used as: n TCP analyzer n User application platform

5. 2000-12-12Marc Emmelmann5 TCP Analyzer n Fundamental Performance Evaluation n Pre-defined set of experiments n Automatic execution n Base for comparing TCP flavors and network effects n Configuration: n Operation System: FreeBSD 4.1 n Testing Tools: DBS, netperf,...

6. 2000-12-12Marc Emmelmann6 User Application Platform n Subjective QoS n Set of “daily life” applications n User interaction n Supplementary performance evaluation n Configuration: n Operation System: Windows, Unix,... n Applications: Web-Browsing, NFS, etc. n Supplementary Tools: tcptrace, tcpdump,...

7. 2000-12-12Marc Emmelmann7 Where We Are... n Test- & Measurement Suite n Simulation Environment n General Aspects n System Parameter n First Simulation Results

8. 2000-12-12Marc Emmelmann8 General Aspects n Independence of demonstrator hardware n Availabiltity only within final phase n Isolate demonstrator (hardware) specifc side effects n Unknown flavors of TCP n Analysis of “large” networks n Adaptation to emerging project constrains n Simulation tool: OPNET modeler / radio n Industry prooven n ATM support n Satellite Orbits can be included n Project specific aspects

9. 2000-12-12Marc Emmelmann9 System Parameters n Satellite Orbit n Bit Rates n Bit Error Rate n Up- & Down-Link Delay n Intra-Satellite Delay n End-to-End Delay

10. 2000-12-12Marc Emmelmann10 Satellite Orbit n Slant Range n Analytical model n Function of orbit altitude n Visibility constrains n Analytical vs. Simulated Distance n STK based simulation compared to theroy n derivation less than 2%

11. 2000-12-12Marc Emmelmann11 Bit Rates Feeder Up & Downlink: 32.768 Mbit/s ISL: 7 - 10 Gbit/s Service Downlink: 32.768 Mbit/s Service Uplink (fixed): 2.048 Mbit/s Service Uplink (portable): 384 kbit/s

12. 2000-12-12Marc Emmelmann12 Bit Error Rate n BER at target system above MAC n Up- & Down-Link n Good weather condition: 2*10E-8 n Rain y causes link to collaps y last for approx. 10 minutes n “on-off” modell n ISLs n Limitations

13. 2000-12-12Marc Emmelmann13 Up- & Down-Link Delay n Based upon analytically gained distance n Comparison analytical vs. simulated delay

14. 2000-12-12Marc Emmelmann14 Intra-Satellite Delay n Final “routes in the sky” still open n Assumed ISLs: n To forward and backward satellite n To left and right neighbor n Simulation based delays

15. 2000-12-12Marc Emmelmann15 End-to-End Delay n Describes aspects of: n Routing behavior “in the sky” n Intercontinental connections n Cooperate networks n Currently not considered n Obtained through final simulations n Reference measurements predict approx 150ms

16. 2000-12-12Marc Emmelmann16 Where We Are... n Test- & Measurement Suite n Simulation Environment n First Simulation Results n Link Model Description n Link Model Verification n RTT Measurement of TCP n Future Steps

17. 2000-12-12Marc Emmelmann17 Link Model Description n Link: n Point-to-point n Symmetrical or asymmetrical n Wired n Delay n Function of time n Deterministic, periodical n Configurable Parameter: n BER n Bit rate

18. 2000-12-12Marc Emmelmann18 Link Model Verification n Delay: y Expected values y Consider queuing delay n Bit rate y Upper Limit

19. 2000-12-12Marc Emmelmann19 RTT Measurement of TCP n Impact of RTT-gain coefficient n Acts as „smoothing“ factor n Considered values y gain = 0.125 y gain = 1 n Results n Derivation less than 1ms n „Smoothed“ curved closer to real round-trip delay variation

20. 2000-12-12Marc Emmelmann20 Future Steps n Timer granularity n Effects of variable delay on throughput n Switch to wireless link model n Better BER model n Simulation of “large” networks n Include ATM-Sat MAC

21. 2000-12-12Marc Emmelmann21 World Wide Web n http://www.fokus.gmd.de y Information about FOKUS n http://www.fokus.gmd.de/cats y Information about the Competence Center CATS n http://www.fokus.gmd.de/cats/projects y Information about the project n http://www.fokus.gmd.de/cats/publ y Download this presentation y Other CATS publications