Development of International e-VBLI Links: Past and Future

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

2. 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)

3. 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

4. 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 UT1, important for military and civilian navigation

5. 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

6. Elements of e-VLBI Development • Develop eVLBI-compatible data system • Mark 5 system development at MIT Haystack Observatory being supported by BKG, EVN, KVN, MPI, NASA, NRAO, NASA, • ~40 units now deployed worldwide • e-VLBI Demonstrations • 1 Gbps e-VLBI using Bossnet (w/ DARPA and NASA support) • ~700km link between Haystack Observatory and NASA/GSFC • First e-VLBI experiment achieved ~788Mbps 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) • Extend e-VLBI connections globally

7. 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 5U chassis • With currently available 250GB disks – capacity of 2TB per ‘8-pack’ module; media cost now ~$1/GB and dropping • GigE connection for real-time and quasi-real-time e-VLBI operations • Inexpensive: <$20K

8. 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

9. International e-VLBI experiments • Westford, MA to Kashima, Japan - experiments in Oct 02, Mar 03, Jun 03 • Files exchanged over Abilene/GEMnet/SuperSinet 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 ~100GB 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

10. 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 • protocol designed to have minimum overhead for in-band data • attention to resource constraints • 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 >20Mbps less than 1% of the time 0.1 0.01 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 • Surfnet – U.S. to Europe at 10 Gbps • IEEAF – U.S. to Europe at 10 Gbps • SuperSinet – U.S. to Japan at 2.5 Gbps • TransPAC – 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

18. 622 Mbps +10 Gbps l Transoceanic donations to IEEAF (in red)

20. 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 and Brazil

21. 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.