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High bit rate tests between Manchester and JIVE

High bit rate tests between Manchester and JIVE. Looking at data rates attainable with UDP along with packet loss and reordering statistics. Simon Casey, Ralph Spencer, Richard Hughes-Jones The University of Manchester. Details of testing. Tests conducted from 1 Nov 2004 – 9 Nov 2004

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High bit rate tests between Manchester and JIVE

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  1. High bit rate tests between Manchester and JIVE Looking at data rates attainable with UDP along with packet loss and reordering statistics Simon Casey, Ralph Spencer, Richard Hughes-Jones The University of Manchester

  2. Details of testing • Tests conducted from 1 Nov 2004 – 9 Nov 2004 • Manchester - Dual Xeon 2.0GHz, Intel Gigabit NIC • JIVE – Mark5A • UDPmon scheduled to run 3 times every 30 minutes, sending packets to JIVE. • 100 000, 1472 byte packets, sent each run with inter-packet spacings of 12us, 18us & 20us.

  3. Attainable bandwidths 12us ~ 890Mbit/s 18us ~ 625Mbit/s 20us ~ 570Mbit/s

  4. Packet loss • 6 runs out of 747 showed any loss • 1097 packets lost out of 81 million sent – 1.3x10-3%

  5. Packet re-ordering

  6. Packet re-ordering • 18us & 20us similar picture – counts ~ 5x fewer • All bar 2 re-ordered packets 1 packet late • Remaining 2 packets late by 2

  7. New Jodrell Fibre connection • 2x1Gbit/s fibres to Manchester became live December 2004 • Previous tests repeated with similar machine in Jodrell as was used in Manchester (Dual Xeon 2.0GHz, Intel Gigabit NIC) • Tests conducted lunchtime 24 Jan 2005 to midnight 26 Jan 2005

  8. Attainable bandwidths 12us ~ 900MBit/s 18us ~ 635MBit/s 20us ~ 575MBit/s

  9. Packet loss • 10 runs showed losses – 9 at 12us spacing, around 0.01% each • Strange loss of almost 2% at 18us • Total 2066 packets lost from 34.8 million – 5.9*10-3%

  10. Conclusions • Overall link quality Manchester/Jodrell to JIVE very good – near line rate possible • Occasional negligible losses, very infrequent noticeable losses • Need monitoring equipment in place to discover point in the link where losses occur • These tests had no ‘exclusive’ access to machines – possible for other users to have an effect • Real eVLBI sessions should be able to control access of machines

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