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					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.
100 000, 1472 byte packets, sent each run with
inter-packet spacings of 12us, 18us & 20us.
                         Attainable bandwidths
                            1472 byte UDP packets, Dual Xeon (Manchester) to
                                             Mark5A (JIVE)
                      950
                      900
Wire rate (Mb/s)




                      850                                       12us
                      800
                                                                18us
                      750
                                                                20us
                      700
                      650
                      600
                      550
                   01/11/2004 12:00                                    09/11/2004 12:00
                                              Time of day


12us ~ 890Mbit/s                          18us ~ 625Mbit/s       20us ~ 570Mbit/s
                             Packet loss
                   1472 byte UDP packets, Dual Xeon (Manchester) to
                                    Mark5A (JIVE)
             1.2

              1

             0.8                                            12us
% Lost




             0.6                                            18us
                                                            20us
             0.4

             0.2

              0
         01/11/2004 12:00                                     09/11/2004 12:00
                                      Time of day

  6 runs out of 747 showed any loss
  1097 packets lost out of 81 million sent – 1.3x10-3%
                      Packet re-ordering
                      1472 byte UDP packets, Dual Xeon
                        (Manchester) to Mark5A (JIVE)
                100
Number out of




                80
                                                12us
   order




                60

                40

                20

                 0

  01/11/2004 12:00                              09/11/2004 12:00
                                Time of day
       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
                       1472 byte UDP packets, Dual Xeon (Jodrell) to
                                      Mark5A (JIVE)
                    1000
 Wire rate (Mb/s)




                     900
                     800                                               12us
                     700                                               18us
                                                                       20us
                     600
    500
 24/01/2005 12:00                                         27/01/2005 00:00
                                        Time of day


12us ~ 900MBit/s                     18us ~ 635MBit/s     20us ~ 575MBit/s
                       Packet loss
               1472 byte UDP packets, Dual Xeon (Jodrell) to
                              Mark5A (JIVE)
           2
         1.8
         1.6                                                   12us
         1.4
% Lost




         1.2                                                   18us
           1                                                   20us
         0.8
         0.6
         0.4
         0.2
           0
24/01/2005 12:00                                    27/01/2005 00:00
                                 Time of day

     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

				
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