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eVLBI Developments at Jodrell Bank Observatory. Ralph Spencer, Richard Hughes-Jones, Simon Casey, Paul Burgess, The University of Manchester. eVLBI Development at JBO and Manchester:. eVLBI correlation tests using actual astronomy data; both pre-recorded and real time data (see talk by Arpad) - PowerPoint PPT Presentation
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eVLBI Developments at Jodrell Bank Observatory
Ralph Spencer, Richard Hughes-Jones, Simon Casey, Paul Burgess,
The University of Manchester
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eVLBI Development at JBO and Manchester:
• eVLBI correlation tests using actual astronomy data; both pre-recorded and real time data (see talk by Arpad)
• Network research:– Why?– How?– Results?
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Why should a radio astronomer be interested in network research?
• Optical fibres have huge bandwidth capability: eMERLIN, eVLA, ALMA, SKA will use >>GHz bandwidths: we need increased bandwidth for VLBI
• Fibre networks are (were) under utilized – can VLBI use spare capacity?
So why study networks?
• What are the bandwidth limits?• How reliable are the links?• What’s the best protocol?• Interaction with end hosts?• What’s happening as technology changes?
Can we get more throughput using switched light paths?
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How? Network Tests: Manchester/JBO to Elsewhere
• High Energy physics (LHC data) and VLBI have the same aims for internet data usage – collaboration!
• iGRID 2002 Manchester-Amsterdam-JIVE, showed that >500 Mpbs flows are possible
• UDP tests on production network in 2003/4• ESLEA Project 2005- use of UKLight• GEANT2 Launch 2005 RESULTS ------------------
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WesterborkNetherlands
Dedicated
Gbit link
EVN-NREN
OnsalaSweden
Gbit link
Jodrell BankUK
DwingelooDWDM link
CambridgeUK
MERLIN
MedicinaItaly
Chalmers University
of Technolo
gy, Gothenbu
rg
TorunPoland
Gbit link
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Gnt5-DwMk5 11Nov03-1472 bytes
0
2
4
6
8
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12
0 5 10 15 20 25 30 35 40Spacing between frames us
% P
acket
loss
Gnt5-DwMk5
DwMk5-Gnt5
Throughput vs packet spacing Manchester: 2.0G Hz Xeon Dwingeloo: 1.2 GHz PIII Near wire rate, 950 Mbps Tests done at different times
Packet loss
CPU Kernel Load sender
CPU Kernel Load receiver
4th Year project Adam Mathews Steve O’Toole
UDP Throughput Manchester-Dwingeloo (Nov 2003)
Gnt5-DwMk5 11Nov03/DwMk5-Gnt5 13Nov03-1472bytes
0
200
400
600
800
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0 5 10 15 20 25 30 35 40Spacing between frames us
Recv W
ire r
ate
Mbits/s
Gnt5-DwMk5
DwMk5-Gnt5
Gnt5-DwMk5 11Nov03 1472 bytes
020406080
100
0 5 10 15 20 25 30 35 40Spacing between frames us
% K
erne
l S
ende
r
Gnt5-DwMk5 11Nov03 1472 bytes
020406080
100
0 5 10 15 20 25 30 35 40Spacing between frames us
% K
erne
l R
ecei
ver
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Packet loss distribution:
( )t
p d
Cumulative distribution
Cumulative distribution of packet loss, each bin is 12 sec wide
Long range effects inthe data?
Poisson
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Exploitation of Switched Lightpaths for E Science
Applications:
• Multi disciplinary project involve collaboration between many research groups: network scientists, computer science, medical science, high energy physicists and radio astronomers: using UKLight network
• Protocol and control plane development• High performance computing• eHealth (e.g. radiology)• High Energy Physics data transfer (LHC)• eVLBI: funds a post-doc (ad out – apply now!)
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26th January 2005 UDP Tests
Simon Casey (PhD project) Between JBO and JIVE in Dwingeloo, using production networkPeriod of high packet loss (3%):
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The GÉANT2 Launch June 2005
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Jodrell BankUK
DwingelooDWDM link
MedicinaItaly Torun
Poland
e-VLBI at the GÉANT2 Launch Jun 2005
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e-VLBI UDP Data Streams
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UDP Performance: 3 Flows on GÉANT• Throughput: 5 Hour run 1500 byte MTU
• Jodrell: JIVE2.0 GHz dual Xeon – 2.4 GHz dual Xeon670-840 Mbit/s
• Medicina (Bologna): JIVE 800 MHz PIII – Mk5 (623) 1.2 GHz PIII 330 Mbit/s limited by sending PC
• Torun: JIVE 2.4 GHz dual Xeon – Mk5 (575) 1.2 GHz PIII
245-325 Mbit/s limited by security policing
(>400Mbit/s 20 Mbit/s) ?
• Throughput: 50 min period• Period is ~17 min
BW 14Jun05
0
200
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800
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0 500 1000 1500 2000Time 10s steps
Rec
v w
ire ra
te M
bit/s
JodrellMedicinaTorun
BW 14Jun05
0
200
400
600
800
1000
200 250 300 350 400 450 500Time 10s steps
Rec
v w
ire ra
te M
bit/s
JodrellMedicinaTorun
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UDP Performance: 3 Flows on GÉANT
• Packet Loss & Re-ordering• Each point 10 secs, 660k packets• Jodrell: 2.0 GHz Xeon
– Loss 0 – 12%– Reordering significant
• Medicina: 800 MHz PIII– Loss ~6%– Reordering in-significant
• Torun: 2.4 GHz Xeon– Loss 6 - 12%– Reordering in-significant
Torun 14Jun04
0
1
2
3
4
5
0 500 1000 1500 2000Time 10s
num
re-o
rder
ed
020000
400006000080000100000
120000140000
num
lost
re-ordered
num_lost
jbgig1-jivegig1_14Jun05
0
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0 500 1000 1500 2000Time 10s
num
re-o
rder
ed
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100000
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num
lost
re-ordered
num_lost
Medicina 14Jun05
0
1
2
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0 500 1000 1500 2000Time 10s
num
re-o
rder
ed0
10000
20000
30000
40000
50000
60000
70000
num
lost
re-ordered
num_lost
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18 Hour Flows on UKLightJodrell – JIVE, 26 June 2005
• Throughput:• Jodrell: JIVE
2.4 GHz dual Xeon – 2.4 GHz dual Xeon
960-980 Mbit/s
• Traffic through SURFnet
• Packet Loss– Only 3 groups with 10-150 lost
packets each– No packets lost the rest of the
time
• Packet re-ordering– None
man03-jivegig1_26Jun05
0
200
400
600
800
1000
0 1000 2000 3000 4000 5000 6000 7000
Time 10s steps
Rec
v w
ire r
ate
Mbi
t/s
w10
man03-jivegig1_26Jun05
900910920930940950
960970980990
1000
5000 5050 5100 5150 5200
Time 10s
Recv w
ire r
ate
Mbit/s w10
man03-jivegig1_26Jun05
1
10
100
1000
0 1000 2000 3000 4000 5000 6000 7000
Time 10s steps
Packet
Loss
w10
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Conclusion
• Max data rates depends on the path:– Limited by end hosts? : lack of cpu power in end host jumbo
packets will help here– Local limits e.g. security : work with the network providers to
achieve the bandwidth we need– Networks have the capacity for >500 Mbps flows– Evidence for network bottlenecks somewhere : more evidence
being collected
• Packet loss will limit TCP flows – explains limits to data rates in EVN eVLBI tests: new protocols will help here
• More needs to be done before we can reliably get 512 Mbps eVLBI in EVN – especially study of end hosts.
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Any Questions?
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