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iGRID2002 Radio Astronomy VLBI Demo.

32 bit words bits vertical. Timestamp. Data. Bit Stream. ~ 7.1 UDP Packets / Data Track Frame. Data Track Frame. iGRID2002 Radio Astronomy VLBI Demo. Web based demonstration sending VLBI data A controlled stream of UDP packets 256-500 Mbit/s on the production network Man  Amsterdam.

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iGRID2002 Radio Astronomy VLBI Demo.

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  1. 32 bit words bits vertical Timestamp Data Bit Stream ~ 7.1 UDP Packets / Data Track Frame Data Track Frame iGRID2002 Radio Astronomy VLBI Demo. • Web based demonstration sending VLBI data • A controlled stream of UDP packets • 256-500 Mbit/s on the production network Man  Amsterdam

  2. European Topology: NRNs, Geant, Sites SURFnet Manchester Jodrell iGrid 2002 JIVE SuperJANET4 CERN

  3. TCP Control Raid0 Disc Raid0 Disc RingBuffer RingBuffer UDP Data Web Interface n bytes  time Wait time The Works:

  4. Incoming packet ids 1 2 3 4 6 1 2 3 4 Move 6 Continue with 7 Receiving Packets • Packets have Header with packet id + Data • Put header directly into control area • Put data directly into ring buffer • No extra copy • Assume UDP packet arrive in order none lost • Deposit data into next consecutive slot • Inspect Header • Move data onward to correct location • Record: • The received inter-packet spacing • 1-way delay Time

  5. 50 bytes UDP Man-UvA Gig 19 May 02 100 bytes 1000 200 bytes 400 bytes 900 600 bytes 800 bytes 800 1000 bytes Recv Wire rate Mbits/s 700 1200 bytes 1472 bytes 600 500 400 300 200 100 0 0 5 10 15 20 25 30 35 40 Transmit Time per frame us UDP Throughput on the Production WAN • Manc-UvA SARA 750 Mbit/s • SJANET4 + Geant + SURFnet • 75% Manchester Access link • Manc-UvA SARA 825 Mbit/s

  6. Acknowledgements • Boston Ltd supply of the SuperMicro servers & donation of SCSI disks and backplane • Dev , Alex Tyagi , Gili-Ross • Brunell University • Peter van Santen • JIVE • Steve Parsley, Sergei Pogrebenko • Metsähovi Radio Observatory • Ari Mujunen • SURFnet & Universiteit van Amsterdam • Pieter de Boer, Erik.Radius, Cees de Laat, Mieke van de Berg • UKERNA • Robin Arrack, Bob Day, Jeremy Sharp • University of Manchester • Richard Hughes-Jones, Ralph Spencer, Paul Burgess • Robin Hughes-Jones Design of web interface (Undergraduate, Oxford University)

  7. Gigabit TCP Throughput on the Production WAN • Throughput vs TCP buffer size • TCP window sizes in Mbytes calculated from RTT*bandwidth

  8. UDP Throughput: SLAC - Man • SLAC – Manc 470 Mbit/s • 75% of the 622 Mbit access link • SuperJANET4 peers with ESnet at 622Mbit in NY

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