High bit rate tests between High bit rate tests between Manchester and JIVEManchester and JIVE

Looking at data rates attainable with Looking at data rates attainable with UDP along with packet loss and UDP along with packet loss and

reordering statisticsreordering statistics

Simon Casey, Ralph Spencer, Richard Hughes-JonesSimon Casey, Ralph Spencer, Richard Hughes-JonesThe University of ManchesterThe University of Manchester

Details of testingDetails of testing

Tests conducted from 1 Nov 2004 – 9 Nov 2004Tests conducted from 1 Nov 2004 – 9 Nov 2004

Manchester - Dual Xeon 2.0GHz, Intel Gigabit Manchester - Dual Xeon 2.0GHz, Intel Gigabit NICNIC

JIVE – Mark5AJIVE – Mark5A

UDPmon scheduled to run 3 times every 30 UDPmon scheduled to run 3 times every 30 minutes, sending packets to JIVE.minutes, sending packets to JIVE.

100 000, 1472 byte packets, sent each run with 100 000, 1472 byte packets, sent each run with inter-packet spacings of 12us, 18us & 20us.inter-packet spacings of 12us, 18us & 20us.

Attainable bandwidthsAttainable bandwidths1472 byte UDP packets, Dual Xeon (Manchester) to

Mark5A (JIVE)

550

600

650

700

750

800

850

900

950

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

Wir

e r

ate

(M

b/s

)

12us

18us

20us

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

Packet lossPacket loss

6 runs out of 747 showed any loss6 runs out of 747 showed any loss

1097 packets lost out of 81 million sent – 1.3x101097 packets lost out of 81 million sent – 1.3x10 -3-3%%

1472 byte UDP packets, Dual Xeon (Manchester) to Mark5A (JIVE)

0

0.2

0.4

0.6

0.8

1

1.2

01/11/2004 12:00 09/11/2004 12:00

Time of day

% L

os

t 12us18us20us

Packet re-orderingPacket re-ordering1472 byte UDP packets, Dual Xeon

(Manchester) to Mark5A (JIVE)

0

20

40

60

80

100

01/11/2004 12:00 09/11/2004 12:00

Time of day

Nu

mb

er

ou

t o

f o

rde

r 12us

Packet re-orderingPacket 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 connectionNew Jodrell Fibre connection

2x1Gbit/s fibres to Manchester became 2x1Gbit/s fibres to Manchester became live December 2004live December 2004

Previous tests repeated with similar Previous tests repeated with similar machine in Jodrell as was used in machine in Jodrell as was used in Manchester (Dual Xeon 2.0GHz, Intel Manchester (Dual Xeon 2.0GHz, Intel Gigabit NIC)Gigabit NIC)

Tests conducted lunchtime 24 Jan 2005 to Tests conducted lunchtime 24 Jan 2005 to midnight 26 Jan 2005midnight 26 Jan 2005

Attainable bandwidthsAttainable bandwidths1472 byte UDP packets, Dual Xeon (Jodrell) to

Mark5A (JIVE)

500

600

700

800

900

1000

24/01/2005 12:00 27/01/2005 00:00Time of day

Wir

e r

ate

(M

b/s

)

12us

18us

20us

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

Packet lossPacket loss1472 byte UDP packets, Dual Xeon (Jodrell) to

Mark5A (JIVE)

00.20.40.60.8

11.21.41.61.8

2

24/01/2005 12:00 27/01/2005 00:00

Time of day

% L

os

t

12us

18us

20us

10 runs showed losses – 9 at 12us spacing, around 0.01% each10 runs showed losses – 9 at 12us spacing, around 0.01% each

Strange loss of almost 2% at 18usStrange loss of almost 2% at 18us

Total 2066 packets lost from 34.8 million – 5.9*10-3%

ConclusionsConclusions

Overall link quality Manchester/Jodrell to JIVE Overall link quality Manchester/Jodrell to JIVE very good – near line rate possiblevery good – near line rate possibleOccasional negligible losses, very infrequent Occasional negligible losses, very infrequent noticeable lossesnoticeable lossesNeed monitoring equipment in place to discover Need monitoring equipment in place to discover point in the link where losses occurpoint in the link where losses occurThese tests had no ‘exclusive’ access to These tests had no ‘exclusive’ access to machines – possible for other users to have an machines – possible for other users to have an effecteffectReal eVLBI sessions should be able to control Real eVLBI sessions should be able to control access of machinesaccess of machines