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High Data Rate Transfer for HEP and VLBI
Ralph Spencer, Richard Hughes-Jones and Simon Casey
The University of ManchesterNetwrokshop33 March 2005
Radio Astronomy• The study of celestial objects at <1 mm to >1m
wavelength.• Sensitivity for continuum sources• B=bandwidth, integration time.• High resolution achieved by interferometers.
Some radio emitting X-ray binary stars in our own galaxy:
B/1
GRS 1915+105 MERLIN
SS433MERLIN and European VLBI
Cygnus X-1VLBA
Earth-Rotation Synthesis
Need ~ 12 hours for full synthesis, not necessarily collecting data for all that time.NB Trade-off between B and for sensitivity.
Telescope data correlated in pairs:N(N-1)/2 baselines Merlin u-v coverage
The European VLBI NetworkEVN
• Detailed radio imaging uses antenna networks over 100s-1000s km
• At faintest levels, sky teems with galaxies being formed
• Radio penetrates cosmic dust - see process clearly
• Telescopes in place …• Disk recording at
512Mb/s• real-time connection
allows greater – response– reliability– sensitivity
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
eVLBI Milestones • January 2004: Disk buffered eVLBI session:
• Three telescopes at 128Mb/s for first eVLBI image
• On – Wb fringes at 256Mb/s
• April 2004: Three-telescope, real-time eVLBI session.
• Fringes at 64Mb/s• First real-time EVN image - 32Mb/s.
• September 2004: Four telescope real-time eVLBI• Fringes to Torun and Arecibo• First EVN, eVLBI Science session
• January 2005: First “dedicated light-path” eVLBI• ??Gbyte of data from Huygens descent
transferred from Australia to JIVE• Data rate ~450Mb/s
• 20 December 20 2004• connection of JBO to Manchester by 2 x 1 GE• eVLBI tests between Poland Sweden UK and Netherlands at 256 Mb/s
• February 2005• TCP and UDP memory – memory tests at rates up to 450 Mb/s(TCP) and 650 Mb/s (UDP)• Tests showed inconsistencies betweeb Red Hat kernals, rates of 128 Mb/s only obtained on 10 Feb• Haystack (US) – Onsala (Sweden) runs at 256 Mb/s
• 11 March Science demo• JBO telescope winded off, short run on calibrator source done• Test needs to be repeated!
Jodrell BankUK
OnsalaSweden
MedicinaItaly
TorunPoland
EffelsbergGermany
WesterborkNetherlands
Telescope connections
JIVE
1Gb/s
1Gb/s
1Gb/s
155Mb/s
MERLIN
CambridgeUK
2.5Gb/s
1Gb/s
MERLINe
?????
Tests on the Network, Manchester-Dwingeloo: investigation of packet loss
• 4th year MPhys Project at The Univertsity of Manchester Oct-Dec 2003, using campus network and SuperJANET 4 academic network in the UK.• UDPmon used to test throughput and packet loss• NB tune up the end machines – see http://grid.ucl.ac.uk/NFNN.html
Effect on the local traffic:
Gnt5-DwMk5 11Nov03-1472 bytes
0
2
4
6
8
10
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 NB record stands at 6.6 Gbps
SLAC-CERN
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
1000
1200
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
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
26th January 2005 UDP Tests
Simon Casey (PhD project) Between JBO and JIVE in Dwingeloo, using production networkPeriod of high packet loss (3%):
The Future:
• eVLBI tests in EVN at ~ 1 per month• Network tests at up to 950 Mb/s – statistics of
packet loss• Investigate alternatives to TCP/UDP – tsunami,
VSI-E etc.• ESLEA tests on MB-NG and UKLight• EXPRes EU eVLBI proposal including
distributed processing, JBO-Onsala test link at 4 Gbps, submitted March 19th 2005
• eVLBI will be routine in 2006!!
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