e-VLBI over TransPAC Masaki HirabaruDavid LapsleyYasuhiro KoyamaAlan Whitney Communications Research Laboratory, Japan MIT Haystack Observatory, USA Communications Research Laboratory, Japan MIT Haystack Observatory, USA

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 Outline

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)

VLBI astronomy example ASTRONOMY Highest resolution technique available to astronomers – tens of microarcseconds Allows detailed studies of the most distant objects 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 Science Plate-tectonic motions from VLBI measurements

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... e-VLBI

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

Typical e-VLBI Data Requirements DescriptionGeodesyAstronomy Duration(hours)24/week Blocks of several contiguous days Telescopes7 (nominal)Up to 20 % Observation Time Data rate(Mbps) Total data collected (/station/day) ~ 1 TB~ 7 TB

Typical e-VLBI Data Requirements

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)

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

Tsunami: Japan  US (disc-to-disc)

Tsunami: Throughput

UDT: Japan  US

UDT Throughput

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

References TSUNAMI – UDT – FAST TCP –

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.

Thank you David Lapsley

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