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e-VLBI over TransPAC

This outline provides an introduction to e-VLBI and its advantages, discusses the typical data requirements, presents e-VLBI experiments conducted to date, and outlines future experiments over TransPAC. It highlights the impact of e-VLBI on traditional VLBI techniques and its applications in astronomy and geodesy. The outline also showcases high-performance transfer protocols used in e-VLBI and provides references for further reading.

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e-VLBI over TransPAC

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  1. e-VLBI over TransPAC

  2. Outline • Introduction • Overview of e-VLBI • Advantages of e-VLBI • Typical e-VLBI data requirements • e-VLBI Experiments to date • Future e-VLBI experiments over TransPAC • Summary of impact of e-VLBI

  3. Traditional VLBI The Very-Long Baseline Interferometry (VLBI) Technique(with traditional data recording on magnetic tape or disk) The Global VLBI Array(up to ~20 stations can be used simultaneously)

  4. VLBI Science • ASTRONOMY • Highest resolution technique available to astronomers – tens of microarcseconds • Allows detailed studies of the most distant objects Plate-tectonic motions from VLBI measurements • GEODESY • Highest precision (few mm) technique available for global tectonic measurements • Highest spatial and time resolution of Earth’s motion in space for the study of Earth’s interior • Earth-rotation measurements important for military/civilian navigation • Fundamental calibration for GPS constellation within Celestial Ref Frame VLBI astronomy example

  5. e-VLBI • Traditional VLBI • Data is recorded onto magnetic media (e.g. tape or hard disk) - currently at 1 Gbps/station • Data shipped to central site • Data correlated - result published 4d - 15 weeks later • e-VLBI • Use the network instead of storage media • Transmit data in real-time or near-real-time from instrument (telescope) to processing center • Many advantages...

  6. Advantages • Scientific: • Bandwidth growth potential for higher sensitivity • Rapid processing turnaround • Practical • Real-time diagnostics • Increased reliability • Lower cost

  7. Typical e-VLBI Data Requirements

  8. Typical e-VLBI Data Requirements

  9. Typical e-VLBI Data Requirements

  10. e-VLBI Experiments to Date • Westford-GGAO e-VLBI results • First near-real-time e-VLBI experiment conducted on 6 Oct 02 • GGAO disk-to-disk transfer at average 788 Mbps transfer rate • Several US to Japan demonstrations • Support of Geodetic e-VLBI experiments: • Up to ~ 100 Mbps sustained for near Real-time data transfer • Sub-24 hour UT1 estimate • Network performance characterization and protocol testing • ~ 600 Mbps transfer rate in Tokyo to US experiment • Recent 500 TB data transfers of real experimental data paving the way for “operationalization” of VLBI transfers • CRF22, CRF23, T2023, T2024 part of IVS schedule • Internet2 Demonstration - October 2003 • ~644 Mbps using FAST TCP • ~400 Mbps using High Speed TCP (HSTCP)

  11. High Performance Transfer Protocols • Tsunami • Rate-based flow control • Data over UDP • Control over TCP • Mark Meiss, Steve Wallace - Indiana University • UDT • Rate-based flow control • Data and Control over UDP • Yunhong Gu, Robert Grossman - University of Illinois • FAST TCP • Windowed, delay-based high performance TCP • Steven Low, et. al • Netlab, Caltech

  12. Tsunami: JapanUS(disc-to-disc)

  13. Tsunami: Throughput

  14. UDT: JapanUS

  15. UDT Throughput

  16. 2004 e-VLBI experimental plan between MIT Haystack and CRL Kashima at 1Gbps e-VLBI server Kashima test server 100km 1G Tokyo XP Koganei 1G TransPAC 1G x2 9,000km Chicago 2.5G MIT Haystack Abilene • Continued experiments using commodity Internet connectivity at Kashima • Experiments using 1 Gigabit per second Internet connectivity at Kashima • Experiments using real-time correlation 1G Los Angeles New York 4,000km 10G • Planned 1 Gbps upgrade at Kashima • Planned 2.5 Gbps upgrade at Haystack

  17. References • TSUNAMI • http://www.indiana.edu/~anml/anmlresearch.html • UDT • https://sourceforge.net/projects/lambdaftp/ • FAST TCP • http://netlab.caltech.edu/FAST/index.html

  18. Summary of Impact of e-VLBI Program • Opens new doors for national and international astronomical and geophysical research. • Represents an excellent match between modern Information Technology and a real science need. • Motivates the development of a new shared-network protocols that will benefit other similar applications. • Drives an innovative IT research application and fosters a strong international science collaboration.

  19. Thank you David Lapsley dlapsley@haystack.mit.edu http://www.haystack.mit.edu

  20. Backup http://www.haystack.mit.edu

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