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Continuing to perfect the SLA measurements at AMS-IX, I looked into syncing the clocks of the measurements probes using PTP. This presentation details the findings.
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Michiel AppelmanNetwork Engineer
MORE-IP Tech Meeting - May 2012
Precision Timing
1
MORE-IP Tech Meeting - May 2012
Previously..
• SLA and KPI’s• Performance Measurements
–ITU-T Y.1731 • Challenges:
–Time Synchronization
2
MORE-IP Tech Meeting - May 2012
Frequency Drift
• Resync of NTP Daemon– Frequency offset maxed out
3
-50.000,00
0
50.000,00
100.000,00
150.000,00
May 5 May 6 May 7 May 8 May 9 May 10 May 11 May 12 May 13 May 14 May 15
ppb
(par
ts p
er b
illion
)
MORE-IP Tech Meeting - May 2012
Frequency Drift
4
-50.000,00
0
50.000,00
100.000,00
150.000,00
May 5 May 6 May 7 May 8 May 9 May 10 May 11 May 12 May 13 May 14 May 15
ppb
(par
ts p
er b
illion
)
• Fixed using firmware upgrade
MORE-IP Tech Meeting - May 2012
Unnatural Phenomenon
• One way delay < 0 µs
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MORE-IP Tech Meeting - May 2012
The flip-side
• One way delay > Two way delay
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MORE-IP Tech Meeting - May 2012
GPS Synchronization
✓Well known✗Not cheap
– Roof access– GPS antennas– Specialized devices
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MORE-IP Tech Meeting - May 2012
SyncE
• Synchronous Ethernet• Layer 1 Technology✗Would require new hardware
– and infrastructure✗Focused on Frequency
– missing phase/time-of-day
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MORE-IP Tech Meeting - May 2012
IEEE1588v2
• Precision Time Protocol✓Requires a clean network✗ or specialized hardware
✓Supported by Accedian• Master/slave protocol
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MORE-IP Tech Meeting - May 2012
PTP Devices
• Two Grandmaster Clocks• Boundary Clocks?
– new switches• Multiple Vendors
– Meinberg• affordable• helpful• 2 test devices
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MORE-IP Tech Meeting - May 2012
Tests
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msw-wes-01 msw-glo-01 msw-glo-02 msw-glo-03 msw-nik-02
msw-sar-02msw-tel-02 msw-eun-02 msw-eqx-01
msw-sar-01
msw-eun-01
msw-ixn-01
msw-tc4-01
msw-tel-01
Platform
MORE-IP Tech Meeting - May 2012
Management Network
12
354,1
354,2
354,3
354,4
354,5
mic
rose
cond
s
• Delay between PTP Master & Slave
MORE-IP Tech Meeting - May 2012
Management Network
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• Phase Offset
-500
0
500
1000
1500
2000
nano
seco
nds
MORE-IP Tech Meeting - May 2012
Phase Offset
• Compared to Best NTP Peer
14
-1.125,00
-750,00
-375,00
0
375,00
750,00
1.125,00
1.500,00
nano
seco
nds
Best NTP PTP
MORE-IP Tech Meeting - May 2012
Phase Offset
• Compared to Worst NTP Peer
15
-20.000,00
-15.000,00
-10.000,00
-5.000,00
0
5.000,00
10.000,00
15.000,00
nano
seco
nds
Worst NTP PTP
MORE-IP Tech Meeting - May 2012
NTP Measurements
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MORE-IP Tech Meeting - May 2012
PTP Measurements
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MORE-IP Tech Meeting - May 2012
Procedure
• Further Testing• Upgrade Accedians
– to support PTP• Move towards PTP
– all at (about) the same time
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MORE-IP Tech Meeting - May 2012
Questions?
19
