Development of International e-VBLI Links Past and Future

Development of International e-VBLI Links: Past and Future Alan R. Whitney MIT Haystack Observatory 1

Traditional VLBI The Very-Long Baseline Interferometry (VLBI) Technique (with traditional data recording) The Global VLBI Array (up to ~20 stations can be used simultaneously) 2

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 3

Scientific Advantages of e-VLBI • Bandwidth growth potential for higher sensitivity – VLBI sensitivity (SNR) proportional to square root of Bandwidth resulting in a large increase in number of observable objects (only alternative is bigger antennas – hugely expensive) – e-VLBI bandwidth potential growth far exceeds recording capability (practical recording data rate limited to ~10 Gbps) • Rapid processing turnaround – Astronomy • Ability to study transient phenomena with feedback to steer observations – Geodesy • Higher-precision measurements for geophysical investigations • Better Earth-orientation predictions, particularly UT 1, important for military and civilian navigation 4

Practical Advantages of ‘e-VLBI’ • Increased Reliability – remove recording equipment out of field – remote performance monitor & control capability in near real-time • Lower Cost – Automated Operation Possible • eliminates manual handling and shipping of storage media – Near Real-time Processing • forestalls growth of storage-capacity requirements with bandwidth growth – Elimination of recording-media pool (millions of $’s!) • Avoid unexpected media-shipping interruptions and losses 5

Elements of e-VLBI Development • Develop e. VLBI-compatible data system – – • e-VLBI Demonstrations – • Mark 5 system development at MIT Haystack Observatory being supported by BKG, EVN, KVN, MPI, NASA, NRAO, NASA, ~40 units now deployed worldwide 1 Gbps e-VLBI using Bossnet (w/ DARPA and NASA support) • ~700 km link between Haystack Observatory and NASA/GSFC • First e-VLBI experiment achieved ~788 Mbps transfer rate VSI-E: Standards for global e-VLBI – Standards for global interoperability are a must for wide deployment of e-VLBI • Establish new protocols for e-VLBI – Adaptive network protocol (newly awarded NSF grant to Haystack Observatory; collaboration with MIT Lab for Computer Science and MIT Lincoln Laboratory); • New IP-based protocol tailored to operate in shared-network ‘background’ to efficiently using available bandwidth • Connect with telescopes worldwide (U. S. , Europe, Japan) • 6 Extend e-VLBI connections globally

Mark 5 VLBI Disk-Based Data System • 1 Gbps continuous recording/playback to/from set of 8 inexpensive (ATA) disks • Mostly COTS components • Two removable ‘ 8 -pack’ disk modules in single 5 U chassis • With currently available 250 GB disks – capacity of 2 TB per ‘ 8 -pack’ module; media cost now ~$1/GB and dropping • Gig. E connection for real-time and quasi-real-time e-VLBI operations • Inexpensive: <$20 K 7

Bossnet 1 Gbps e-VLBI demonstration experiment (Fall 2002) • 788 Mbps e-VLBI transfer achieved, but took much tuning • Full report at www. haystack. edu/e-vlbi Future Initial experiment 8

International e-VLBI experiments • Westford, MA to Kashima, Japan - experiments in Oct 02, Mar 03, Jun 03 – Files exchanged over Abilene/GEMnet/Super. Sinet networks • Best achieved so far ~107 Mbps – Correlation on Mark 4 correlator at Haystack and PC Software correlator at Kashima; nominal fringes obtained – Further experiments are scheduled; active network testing is in progress • Kauai, Hawaii to Wettzell, Germany (in progress) – Daily experiments of ~100 GB are ideal candidate for early e-VLBI – Data will be transferred to Haystack Observatory for processing (OC-3 speeds are possible) – Network links are now being developed 9

RTP Capabilities • RTP provides an Internet-standard format for: – – – • • Transmission of sampled analog data Dissemination of session information Monitoring of network and end system performance (by participants and third parties) Adaptation to varying network capability / performance Message Sequencing / reordering Multi-cast distribution of statistics, control and data RTP allows the reuse of many standard monitoring / analysis tools RTP seen as internet-friendly by the network community: – attention to efficiency • – attention to resource constraints • – protocol designed to have minimum overhead for in-band data won't use up all your bandwidth with control information attention to scaling issues RTCP Capabilities • Monitors network’s real-time data delivery performance • Statistics collected from receivers • Information delivered to –Senders (adapt to prevailing conditions) –Network management (identifies faults, provisioning problems) • Adaptive, bandwidth-limited design 11

Possible VSI-E Topologies 12

New Application-Layer Protocols for e-VLBI • Based on observed usage statistics of networks such as Abilene, it is clear there is much unused capacity • New protocols are being developed which are tailored to e-VLBI characteristics; for example: – Can tolerate some loss of data (perhaps 1% or so) in many cases – Can tolerate delay in transmission of data in many cases • ‘Experiment-Guided Adaptive Endpoint’ (EGAE) strategy being developed at Haystack Observatory under 3 -year NSF grant: – Will ‘scavenge’ and use ‘secondary’ bandwidth – ‘Less than best effort’ service will not interfere with high-priority users – Dr. David Lapsley has joined Haystack staff to lead this effort 13

Typical bit-rate statistics on Abilene network 1. 0 Usage >20 Mbps less than 1% of the time 0. 1 0. 001 100 500 Mbps Conclusion: Average network usage is only a few % of capacity 14

Typical distribution of heavy traffic on Abilene 1. 0 0. 9 0. 8 0. 7 <10% of ‘bulk’ transfers exceed ~100 secs 200 400 1000 secs Conclusion: Heavy usage of network tends to occur in bursts of <2 minutes 15

Possible International Connections • • 16 Surfnet – U. S. to Europe at 10 Gbps IEEAF – U. S. to Europe at 10 Gbps Super. Sinet – U. S. to Japan at 2. 5 Gbps Trans. PAC – U. S. to Japan at 655 Mbps (2 links) GEMNET – U. S. to Japan at 150 Mbps (operated by NTT) AMPATH – U. S. to S. America (mostly OC-3 – 155 Mbps) Australia – Hawaii – U. S. : 10 Gbps link under consideration

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622 Mbps +10 Gbps l Transoceanic donations to IEEAF (in red) 19

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AMPATH: Research and Education Network and International Exchange Point for the Americas · · Launched in March 2000 as a project led by Florida International University (FIU), with industry support from Global Crossing (GX), Cisco Systems, Lucent Technologies, Juniper Networks and Terremark Worldwide Enables wide-bandwidth digital communications between the Abilene network and 10 National Research and Education Networks (NRNs) in South and Central America, the Caribbean and Mexico Provides connectivity to US research programs in the region AMPATH is a project of FIU and the National Science Foundation’s Advanced Networking Infrastructure & Research (ANIR) Division Note: VLBI telescopes currently in Chile 21 and Brazil

Impact of e-VLBI Program • Opens new doors for 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 protocol that will benefit other similar applications. • Drives an innovative IT research application and fosters a strong international science collaboration. 22