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IGRID2002 Radio Astronomy VLBI Demo. uWeb based demonstration sending VLBI data A controlled stream of UDP packets 256-500 Mbit/s on the production network.

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Presentation on theme: "IGRID2002 Radio Astronomy VLBI Demo. uWeb based demonstration sending VLBI data A controlled stream of UDP packets 256-500 Mbit/s on the production network."— Presentation transcript:

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

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

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

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

5 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 uBoston Ltd supply of the SuperMicro servers & donation of SCSI disks and backplane Dev, Alex Tyagi, Gili-Ross uBrunell University Peter van Santen uJIVE Steve Parsley, Sergei Pogrebenko uMetsähovi Radio Observatory Ari Mujunen uSURFnet & Universiteit van Amsterdam Pieter de Boer, Erik.Radius, Cees de Laat, Mieke van de Berg uUKERNA Robin Arrack, Bob Day, Jeremy Sharp uUniversity 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 LinkRound trip time ms TCP Window for BW 1 Gbit/s TCP Window for UDP BW 750 Mbit/s TCP Window for UDP BW 460 Mbit/s Man – Ams Man - CERN

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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