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NTP, TIME -- HOW AND WHY?
Patrik Fältström
Head of Research and Development
Netnod
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Why is time important?
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Accuracy
High
Low
Low
High
Precision
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Accuracy
High
Low
Low
High
Precision
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TAI
GPS
time values
UTC
UT1
leap sec intervals
1st Jan 1958
UTn
UT1
UTC
6th Jan 1980
elapsed time
GPS
<0.3s <0.9s
TAI
19 s
36 s
From July 1, 2015
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Why is it important to know what time it is?
You and I agree on having dinner together at Brasserie Godot
We need to coordinate location in four dimensions
Same coordinates, including the same time scale
Photo by Ryan Pikkel (CC)
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Multiple non-synchronized events
Event
Event
00:00:03
00:00:01
Storage
Event
00:00:05
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Multiple non-synchronized events
Event
Event
00:00:03
00:00:01
Storage
Event
00:00:05
In what order did the events take place?
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More seriously...
If one have any kind of transaction system, the time stamps must be
precise enough that the order of the transactions is non-disputable.
1 kap. 5 § Handelsbalken (1736:0123 2):
• 5 § Säljer man tvem ett; gälde skadan åter, (och böte tio daler,) och den
behålle godset, som först köpte.
EuroSOX - Information Lifecycle Management:
• Operational aspects of ILM include backup and data
protection; disaster recovery, restore, and restart; archiving
and long-term retention; data replication; and day-to-day
processes and procedures necessary to manage a storage
architecture.
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Nuvarande klocksystem
What do Netnod do use today?
RB1 E1
RB2 E1
1-pps
10 MHz
GPS
E1 Distr.
multi-mode fiber
1-pps
RS232
RB1 RB2 RB3 RB4
Switch
1-pps
10 MHz
1-pps
Switch
TIC
RS232
1-pps
10 MHz
CTRL1 E1
CTRL2 E1
1-pps
NTP1
NTP2
Data hämtas till SP för spårbarhetsberäkning och presentation.
System klarar sig utan GPS under ca 1 månad.
CTRL
SP
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What precision do we reach?
As you can see, we today stay within 10-6 seconds
New design is targeted at much better quality
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Last 10 years in Sweden
Government launched an investigation:
• Investigation about legal metrology, time and frequency and provisioning of
a National Meteorology Center (N 2006:14) This investigation requested a special report on time:
• Traceable time and frequency - perfekt tajmat
• http://www.regeringen.se/sb/d/8896/a/90126 Samverkansgruppen för informationssäkerhet (SAMFI) created:
• Samhällets informationssäkerhet, Nationell handlingsplan 2012
• https://www.msb.se/RibData/Filer/pdf/26290.pdf
• Det nationella systemet för robust och spårbar tid vidareutvecklas.
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In practice
SP Technical Research Institute of Sweden
• http://www.sp.se/en/units/measurement/time_frequency/Sidor/default.aspx
• Works with next generation NTP-service
• Including time transfer without dependency of GNSS Netnod
• http://www.netnod.se/other/valueadd/ntp
• Together with SP, financed by PTS, is building a new system
• NTP
• IEEE1588v2
• Both time and frequency
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Timeline
The project will build distribution ondes in Stockholm, Gothenburg,
Malmö and Sundsvall during 2015 and in Luleå 2016
Stockholm, Malmö, Sundsvall is installed
Gothenburg installed October 2015
Goal is to start delivery of services end of 2015
End of project is December 15, 2015
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What is a node delivering
NTP
Developed NTP in FPGA
IPv4 and IPv6
At least 10Gbps
Signed NTP using symmetric keys
PTP (1588v2)
One profile
Frequency
1PPS, 5MHz and 10MHz
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Comparison of time
How do we know we have the right time in a node?
Transfer and compare time via satellite
Transfer and compare time via PTP (over SUNET)
Have traceability against UTC(SP)
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Redundancy
Each node have an A and B side
Ability to run without power?
Each node have UPS and battery, plus extra batteries for Cesium
Precision over time?
Each node should stay within 250ns even if it is isolated for 6 months
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References:
From Sundials to Atomic Clocks: Understanding Time and Frequency,
Jespersen, James and Jane Fitz-Randolph, (http://tf.nist.gov/general/
pdf/1796.pdf – 26 MB, 306 pages) 2nd (revised) edition, Mineola, New
York: Dover Publications, 1999 ISBN 0-16-050010-9
Longitude: The True Story of a Lone Genius Who Solved the Greatest
Scientific Problem of His Time, Dava Sobel 1995, Walker Publishing
Company, Inc., New York, ISBN 0-8027-1312-2
Elektronisk signering, En antologi, Redaktör: Jon Kihlman. Stockholm,
Sweden: Nordstedts Juridik, 2013. ISBN: 978-913901731-8
Patrik Fältström - [email protected]
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