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Masaki Hirabaru and Yasuhiro Koyama {masaki,koyama}@nict.go.jp

International e-VLBI Experience. PFLDnet 2006 Febrary 2, 2006. Masaki Hirabaru and Yasuhiro Koyama {masaki,koyama}@nict.go.jp. radio signal from a star. delay. A. B. Large Bandwidth-Delay Product Network issue. A/D. clock. A/D. clock. ~Gbps. ~Gbps. Internet. d. A.

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Masaki Hirabaru and Yasuhiro Koyama {masaki,koyama}@nict.go.jp

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  1. International e-VLBI Experience PFLDnet 2006 Febrary 2, 2006 Masaki Hirabaru and Yasuhiro Koyama{masaki,koyama}@nict.go.jp

  2. radio signal from a star delay A B Large Bandwidth-Delay Product Network issue A/D clock A/D clock ~Gbps ~Gbps Internet d A correlator B e-VLBI (Very Long Baseline Interferometry) • e-VLBI geographically distributed observation, interconnecting radio antennas over the world ASTRONOMY GEODESY

  3. VLBI - Characteristics • Observing Bandwidth  (Precision of Time Delay)-1  (SNR)1/2  Data rate • Wave Length / Baseline Length  Angular Resolution • Baseline Length  (EOP Precision)-1 Faster Data Rate = Higher Sensitivity Longer Distance = Better Resolution

  4. Recent e-VLBI System Developments K5 by NICT ADS1000 (1024Msample/sec 1ch 1bit or 2bits) Correlator other DAS PC-VSI Board (Supports VSI-H specifications) Internet VSI-H VSI-E VTP(RTP/RTCP) IP-VLBI Board (~16Msample/ch·sec, ~4ch, ~8bits) ADS2000 (64Msample/ch·sec, 16ch, 1bit or 2bits) PC

  5. Real-time e-VLBI – flat-rate live data streaming Internet Correlation Synchronize e-VLBI Data Transfer Traditional e-VLBI – file transfer Carry a disk to the nearest stationto put on-line

  6. Typical Network Usage • Traditional e-VLBI (off-line)- File transfer e.g. 64 Mbps x 24 hours = 691 GB e.g. 512 Mbps x 2 hours = 460 GB • Quasi-Real-time- Turnaround time (observation + transfer + correlation) e.g. 4.5 hours for UT1-UT • Periodical (e.g. once a week) - Utilize available b/w • Real-time - two one-way streaming- loss allowance depending on S/N (~0.1% OK)- time allowance to retransmit (~ sec?)- e.g. Huygens tracking

  7. Transfer Examples • NICT, JP - Haystack, US (Aug. 2003) ~100 Mbps by TCP [parallel] • [test] JIVE, NL – NICT, Japan (Dec. 2004) by HUT ~400Mbps by tsunami • CISRO, AU – JIVE, NL (Jan. 2005) by AARNET ~450 Mbps by TCP over UCLP • [test] Haystack,US - NICT, JP (Jan. 2005) ~700 Mbps by TCP • [no fringe] NICT, JP - Haystack, US (SC2005) ~512Mbps by VTP (RTP) via GMPLS

  8. TCP Experience • A single flow TCP did not get the performance as expected because the network is designed with a short queue (cheap?) L2/L3 switch.The queue holds for ~1ms (Routers ~100 ms or more) a) Bottleneck b) Bottleneck VLANs Switch Router Switch Router 1Gbps (10G) 100Mbps(1G) Queue~100p Queue~10000p

  9. UDP Experience • Difficulty in rate-control: Bursts from data source one sec. interval shaped? PCIBoard CPU/MEM Network • Difficulty in identifying a location of lost packets along a path

  10. Future e-VLBI Data Transfer multicast and automated Correlate among many combinations concurrently to get more precise data (like a virtual huge antenna)

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