© 2016 ADVA Optical Networking. All rights reserved. Confidential.1

In-Service Monitoring of PTP Performance

Dominik Schneuwly, 24th October 2016

© 2016 ADVA Optical Networking. All rights reserved. Confidential.2

Outline

• Introduction

• Sampling the Network Sites

• Probing Techniques

• Reduction of Data Quantity

• Easy-to-Use Representation of Results

• Conclusion and Outlook

© 2016 ADVA Optical Networking. All rights reserved. Confidential.3

What Are We Talking About?

• Purpose: Monitor the performance of network in real time, raise an alarm when an action for preserving the performance is required

• Means:

• Permanent installation of sync probes in selected sites

• Continous collection of measurement results

• Anaysis and consolidation of the results into a form which is useful to the network operator (operations and maintenance or network planning)

• Subsequent actions:

• Short term actions: traffic engineering in a broader sense; examples: QoS, etc.

• Long term actions: additional investment in synchronization; examples: functional upgrades of equipment, etc.

© 2016 ADVA Optical Networking. All rights reserved. Confidential.4

Sync Probing Infrastructure

NENENENENENE GM

GNSS

NE

Probe

GNSS

Probe

GNSS

Probe

GNSS

eNode B

Probe

GNSS

Data Base

Analysis

Presentation

Data collection channel

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Sync Probing Infrastructure

• Probe: Tool located in the network for the acquisition of measured data

• Challenge: Density of probes vs cost

• Data collection channel:

• Challenge: Limitation of used traffic data rate (bandwidth)

• Data base: Storage of measured data

• Challenge: Limitation of stored data quantity

• Analysis: Processing of the measured data and automatic interpretation

• Challenge: Amount of data processing

• Presentation: Visual presentation of processed results in an easy-to-use format

• Challenge: Understandable and usable presentation

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Sampling the Network Sites

• Sampling: Choosing a reasonable number of probe installation sites

• Two questions:

• How many? Depends on gain/cost ratio - see upcoming slides

• Where? Adopt a sampling strategy!

• Sampling strategies:

• Random

• Worst case sites, i.e. cell sites

• Impact-based: privilege sites where bad performance has strong impact

• Witness path: take a representative path and probe on all sites along the path

• On sites with BC or APTSC: re-use existing hardware by adding probing function

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Sampling Strategy: Cell Sites

S

S S

S

S

SS

SS

S

S

S

S

S S

S

S SS

S

S

S

SS

S

SS

S

S

S

S

S

S

S

S

S

SS

S

S

S

S

GM

GNSS

Probe

GNSS

Probe

GNSS

Pro be

GNSS

Probe

GNSS

Probe

GNSS

Probe

GNSS

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Sampling Strategy: BC / APTSC Sites

S

S S

S

S

SS

SS

S

S

S

S

S S

S

S SS

S

S

S

SS

S

SS

S

S

S

S

S

S

S

S

S

SS

S

S

S

S

GM

GNSS

Probe

GNSS

Pro be

GNSS

Pro be

GNSS

Probe

GNSS

Probe

GNSS

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Sampling Strategy: Along a Path

N

max│TE│

eNode BNENENENENENENE

Probe

GNSS

Probe

GNSS

Probe

GNSS

Probe

GNSS

1.1 μs

At different times of the day, i.e. with different traffic loads

GM

GNSS

NE

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Probing a Slave Clock – Physical Output

4 Slave’s physical output signal can be monitored vs. GNSS

GNSS

Slave Clock(DUT)

T1T4 T3

10 MHz/BITS/SyncE

T1T4 T3

1PPS

T-GM

Network

CLK TIE and 1PPS Time Error

CLK and 1PPS MTIE

Sync Probe

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T1T4

Probing a Slave Clock – Passive Probing

GNSS

Slave Clock(DUT)

T3

T1T4

T3

T3

Packet MTIE

Packet Time ErrorT-GM

Network

Sync Probe

• The sync probe is placed at a calibrated distance from the slave clock• The sync probe functions as a passive PTP probe (fiber tapping or mirroring switch)• Probing is based on T3 embedded in the PTP delay request messages

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Probing a Boundary Clock – Active Probing

• The sync probe is placed at a calibrated distance from the master port of the boundary clock

• The sync probe functions as slave clock and performs measurements at the same time (active PTP probe)

• Probing is based on T1 & T4 embedded in the PTP sync messages

Boundary Clock(DUT)

Slave Clock

T1T4 T3

T1 T4

T3

T1T4

Packet MTIE

Time Error

T3

T-GM

GNSS

Sync Probe

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T1T4

Probing a Boundary Clock – Passive Probing

Boundary Clock(DUT)

Slave Clock

T3

T1T4

T3

T1

Packet MTIE

Packet Time ErrorT-GM

GNSS

Sync Probe

• The sync probe is placed at a calibrated distance from the master port of the boundary clock

• The sync probe functions as passive PTP probe (fiber tapping or mirroring switch)• Probing is based on T1 & T4 embedded in the PTP sync messages

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Distribution of Data Processing

• How much data processing in the probe?

• How much data processing in the analyzer?

• Has an impact on:

• Total cost of N probes

• Cost of analyzer

• Quantity of data to be transfered (from probes to data base) and stored (in data base)

Metric calculation InterpretationPre-processing

2wayTE

calculation

TEFWD

TEREV e.g.:peak-to-peakMTIEetc.

e.g.:comparing with mask

e.g.:packet selection

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Distribution of Data Processing

• System cost (CAPEX) vs cost of traffic bandwith (OPEX)

• Typical optimization problem seen in network function virtualization (NFV)

• General tendency in NFV: centralizing processing functions

• Sync probing is getting more accessible

All inProbe

All inAnalyzer

Traffic bandwidth

EquipmentCost

Cost of n Probes

Cost of Analyzer

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Presentation of the Results

• An easy-to-use presentation is key!

• Must help in deciding corrective actions

• Examples:

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What to Do With the Results

Presentation of the results is action-oriented; two action fields:

• Operations and maintenance:

• Act upon configurable parameters, software, etc.

• E.g., traffic engineering, QoS, load balancing, adapting packet rates, adapting flow networking, etc.

• Repairs

• Short term (minutes, hours)

• OPEX related

• Network expansion:

• Act upon network infrastructure (equipment, systems)

• Upgrading, expansion, replacement

• Network planning

• Mid to long term (months)

• CAPEX related

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Conclusion and Outlook

• In-service monitoring of sync complements the supply of sync

• In-service monitoring of sync is as necessary as ever

• Miniaturization and advanced data processing make sync probing more accessible

• Network function virtualization (NFV) will play an increasingly important role

© 2016 ADVA Optical Networking. All rights reserved. Confidential.19

Thank You

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