Chip Webb, CTO from Anue Systems- a leader in test and measurement solutions, presented new ITU-T recommendations that relate to floor population metrics are emerging, including G.8260, G.8261.1 and G.8263. Network limits as well as slave tolerance limits are presented. At the Workshop on Synchronization in Telecommunications Systems (WSTS in Broomfield, Colorado) was a call for improved testing standards, new models for supporting today’s network timing devices and new methods for reducing network errors, in a series of presentations Network and wireless providers are under intense pressure to meet the demands for reliable information access with increased network bandwidth. This increasing demand requires network providers to ensure the accuracy of packet information shared across the network. Network “noise”, increased traffic and other factors can affect the ability of the network to accurately track data, resulting in a number of issues, such as lost or missing information or dropped calls on wireless networks.

1. A short introduction to the new “Floor Population” Metrics
WSTS 2012
Chip Webb
CTO
© Copyright 2002-2012 Anue Systems, Inc.

2. A short introduction to the new “Floor Population” Metrics
► Introduction
► Objective
► Lucky Packets
► Metric Definitions
► Floor Window
► PDV Performance Limits
► Example Measurement
► Conclusion
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3. Introduction
►What are the new metrics?
• Floor Packet Count (FPC)
• Floor Packet Percentage (FPP)
• Floor Packet Rate (FPR)
►Where are they used? New ITU Recommendations
• Defined in G.8260
• Used in G.8261.1 as a network limit (1%)
• Used in G.8263 as a slave tolerance limit (1% at slave spec’d min rate)
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4. Packet Timing System
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5. Packet Timing System
(a more abstract view)
Packet Network
Master Slave
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6. Packet Timing System
(a more abstract view)
Packet Network
Master Slave
The Floor Population Metrics are a way to measure
Packet Delay Variation (PDV) in this system
(NOTE: Other metrics, such as MAFE are also possible)
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7. A short introduction to the new “Floor Population” Metrics
► Introduction
► Objective
► Lucky Packets
► Metric Definitions
► Floor Window
► PDV Performance Limits
► Example Measurement
► Conclusion
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8. Objective of the new metrics (from G.8260)
►To study the population of timing packets within a
certain fixed cluster range starting at the observed
floor delay
►To compare the population with acceptance or
rejection thresholds
►To ensure that at least a minimum number of
packets, or a minimum percentage of packets
remains within the specified cluster range starting at
the observed floor delay
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9. Objective of the new metrics
To measure so-called “Lucky Packets”
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10. A short introduction to the new “Floor Population” Metrics
► Introduction
► Objective
► Lucky Packets
► Metric Definitions
► Floor Window
► Performance Limits
► Example Measurement
► Conclusion
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11. Quiz: Which of these shows Lucky Packets?
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12. Quiz: Which of these shows Lucky Packets?
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13. Quiz: Which of these shows Lucky Packets?
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14. Lucky Packets
►Lucky packets are the packets that experience near minimum delay
• They spend little or no time waiting in queues
• They are fortunate to avoid congestion in the network
►Therefore lucky packets can be selected using a “cluster range”
• Anchored at the minimum delay (observed or known)
• Size of the cluster range affects the sensitivity of the measurement
►Cluster range is also called “Floor Window”
• More on that in a minute
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15. A short introduction to the new “Floor Population” Metrics
► Introduction
► Objective
► Lucky Packets
► Metric Definitions
► Floor Window
► PDV Performance Limits
► Example Measurement
► Conclusion
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16. Metric Definitions
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17. Metric Definitions
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18. Metric Definitions
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19. Metric Definitions
• Game lasted 1 minute
• Three darts thrown
• Two hit Bull’s Eye
• 1 point for Bull’s Eye
STATS
• Score=2
• Percent=67% (2/3)
• Rate=2/minute
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20. Metric Definitions via Dart Board Analogy
►Floor Packet Count (FPC)
• The number of times a dart landed in the Bull’s Eye
►Floor Packet Percentage (FPP)
• The percentage of times a dart landed in the Bull’s Eye
►Floor Packet Rate (FPR)
• The rate that darts land in the Bull’s Eye (e.g. per minute or hour)
Note: Full
►To apply to packet timing systems:
mathematical
• Replace “dart” with “timing packets”
definitions are
• Replace “land” with “have delay” (or “are delivered”) in backup
• Replace “Bull’s Eye” with “Floor Window” slides
 (size of Bull’s Eye is analogous to the “cluster range”
20 © Copyright 2002-2012 Anue Systems, Inc.

21. A short introduction to the new “Floor Population” Metrics
► Introduction
► Objective
► Lucky Packets
► Metric Definitions
► Floor Window
► PDV Performance Limits
► Example Measurement
► Conclusion
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22. The floor window
(a.k.a. the Bull’s Eye)
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23. The Floor Window
(a.k.a. the Bull’s Eye)
►Window has width, height and vertical position
• Width is defined as 200 seconds 200 seconds
Window
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24. The Floor Window
(a.k.a. the Bull’s Eye)
►Window has width, height and vertical position
• Width is defined as 200 seconds 200 seconds
• Height is defined as 150 microseconds
Window
(NOTE: Not drawn to scale)
Floor
150 s
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25. The Floor Window
(a.k.a. the Bull’s Eye)
►Window has width, height and vertical position
• Width is defined as 200 seconds 200 seconds
• Height is defined as 150 microseconds
• Position of window is based
on minimum observed delay
Window
(NOTE: Not drawn to scale)
Floor
150 s
Minimum
delay
(NOTE: Anue does not take a position on the suitability of specific window parameter values)
25 © Copyright 2002-2012 Anue Systems, Inc.

26. A short introduction to the new “Floor Population” Metrics
► Introduction
► Objective
► Lucky Packets
► Metric Definitions
► Floor Window
► PDV Performance Limits
► Example Measurement
► Conclusion
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27. Network PDV Limit (G.8261.1)
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28. Network PDV Limit
Packet Network
Master Slave
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29. Network PDV Limit
FPP ≥ 1%
Packet Network
Master Slave
NOTE: This is a relative measurement
and doesn’t depend on timing packet rate
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30. Network PDV Limit
FPP ≥ 1%
Packet Network
Master Slave
NOTE: This is a relative measurement
and doesn’t depend on timing packet rate
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31. Slave PDV Tolerance (from G.8263)
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32. Slave PDV Tolerance
Packet
Rate
Master Packet Network Slave
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33. Slave PDV Tolerance
FPP ≥ 1%
Packet
Rate
Master Packet Network Slave
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34. Slave PDV Tolerance
FPP ≥ 1%
Packet
Rate
Master Packet Network Slave
FPC
FPR
NOTE: This is an absolute measurement
that depends on timing packet rate
34 © Copyright 2002-2012 Anue Systems, Inc.

35. A short introduction to the new “Floor Population” Metrics
► Introduction
► Objective
► Lucky Packets
► Metric Definitions
► Floor Window
► PDV Performance Limits
► Example Measurement
► Conclusion
35 © Copyright 2002-2012 Anue Systems, Inc.

36. Example Measurement
►Packet timing system operating at 32 packets per second
►Packet Delay Variation (PDV) based on flicker noise
►Low level of random packet loss (0.01%)
►Brief network outage (80 seconds)
►Steps for calculating FPC, FPP & FPR
• Find minimum delay
• Draw FPC graph, explain axes
• Calculate with jumping window
• Calculate with sliding window
• Compare jumping and sliding
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37. Example: Flicker PDV and 0.01% Loss (@32 pkt/sec)
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38. Search for minimum delay value
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39. Draw horizontal line for minimum delay
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40. Draw the Floor Window
200 Seconds
150 seconds
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41. Add the FPC graph
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42. Add the FPC graph
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43. Look at just the FPC Axis
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44. Look at just the FPC Axis
Smallest countable
value is one packet
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45. Look at just the FPC Axis
Largest possible
value is 6400 pkt.
(32pkt/sec * 200 sec)
Smallest countable
value is one packet
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46. Look at just the FPC Axis
Largest possible
value is 6400 pkt.
(32pkt/sec * 200 sec)
Axis has
logarithmic
scale
Smallest countable
value is one packet
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47. Compare FPC to FPP
Largest possible
value is 6400 pkt.
(32pkt/sec * 200 sec)
Smallest countable
value is one packet
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48. Compare FPC to FPP
Largest possible 6400 pkt
value is 6400 pkt. is 100%
(32pkt/sec * 200 sec)
Smallest countable
value is one packet
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49. Compare FPC to FPP
Largest possible 6400 pkt
value is 6400 pkt. is 100%
(32pkt/sec * 200 sec)
64 pkt
is 1%
Smallest countable
value is one packet
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50. Compare FPC and FPP to FPR
Largest possible
value is 6400 pkt.
(32pkt/sec * 200 sec)
Smallest countable
value is one packet
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51. Compare FPC and FPP to FPR
Largest possible 32 pkt/sec is max
value is 6400 pkt. (same as 100% FPP)
(32pkt/sec * 200 sec)
Smallest countable
value is one packet
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52. Compare FPC and FPP to FPR
Largest possible 32 pkt/sec is max
value is 6400 pkt. (same as 100% FPP)
(32pkt/sec * 200 sec)
1% is 0.32pkt/sec
and is 64 pkt
Smallest countable
value is one packet
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53. Draw the 1% FPP Limit Line
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54. Draw the 1% FPP Limit Line
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55. Calculate Floor Population with Jumping Window
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56. Calculate Floor Population with Jumping Window
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57. Calculate Floor Population with Sliding Window
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58. Calculate Floor Population with Sliding Window
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59. Compare: Jumping/Sliding
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60. 60 © Copyright 2002-2012 Anue Systems, Inc.

61. Conclusion
►Three new related metrics for “Lucky Packets”
• FPC (Floor Packet Count) [How many darts hit the Bull’s Eye?]
• FPP (Floor Packet Percent) [What percent of darts hit the Bull’s Eye?]
• FPR (Floor Packet Rate) [How often do the darts hit the Bull’s Eye?]
►PDV Limit is FPP ≥ 1%
• Window width is 200 sec.
• Window height is 150us
►Two ways to calculate (depending on amount of window overlap)
• Jumping windows
• Sliding windows
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62. Thank You! Questions?
cwebb@anuesystems.com
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63. Backup Slides
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64. Formal Mathematical Definition of the new Metrics
►x[i] is the measured latency of timing packet i,
• 0 ≤ i < N. (i.e. there are N packets in the data set
► Pis the nominal time between timing packets
► is the cluster range (vertical window height)
►W represent the window interval (horizontal window width)
• It can also be expressed as K samples, K = W/ P.
Note: It is assumed that the packet rate of the timing flow is nominally
constant. The case for a variable rate of packet transmission is for
further study.
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65. Mathematical Definition of the Metrics
►Step 1: Find the minimum delay packet
►Step 2: Calculate the indicator function
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66. Mathematical Definition of the Metrics (cont.)
►Step 3: Count the packets in the window (FPC)
►Step 4: Express this result as a packet rate (FPR)
►Step 5: Also express as a percentage (FPP):
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67. Absolute and Relative Metrics
►FPP is a relative metric
• Calculation does not depend on the timing packets rate
• Relative means that the metric tells us what has changed between
reference planes.
►FPC and FPR are absolute metrics
• Calculation depends on the rate at which timing packets are sent
►Network performance is best measured as a relative limit
• FPP compares the network output relative to its input
• Since the network doesn’t create the packets, can’t be absolute
►Slave performance is best measured with an absolute limit
• FPC or FPR
• But G.8263 refers to G.8261.1 limit at a given packet rate (still absolute)
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68. Slave PDV Tolerance Limit is actually an absolute level
Pkt Rate
PEC-S-F
Packet Rate
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69. Slave PDV Tolerance Limit is actually an absolute level
Pkt Rate
PEC-S-F
Packet Rate
99%
Actual
PEC-S-F
1% FPR Limit
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70. Slave PDV Tolerance Limit is actually an absolute level
Pkt Rate
e.g. 32 pkt/sec.
PEC-S-F The range of
Packet Rate acceptable packet
rates is implementa-
tion dependent.
99%
Actual
PEC-S-F
1% FPR Limit
e.g. 0.32 pkt/sec.
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71. Slave PDV Tolerance Limit is actually an absolute level
Pkt Rate
e.g. 32 pkt/sec.
PEC-S-F The range of
Packet Rate acceptable packet
rates is implementa-
tion dependent.
99%
Actual
PEC-S-F
1% FPR Limit
NOTE: This is an e.g. 0.32 pkt/sec.
absolute measurement NOTE: But it allows different
because it depends on PEC-S-F implementations to
timing packet rate. have different limits.
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