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 Manchester - Dual Xeon 2.0GHz, Intel Gigabit NIC JIVE – Mark5A UDPmon scheduled to run 3 times every 30 minutes, sending packets to JIVE , 1472 byte packets, sent each run with inter-packet spacings of 12us, 18us & 20us.

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

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

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

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

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

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 %

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