Timing signal Significant instants Timing jitter and time · Doc. CX5012 v2.1 Page 3 of 15 © Calnex Solutions Timing jitter and wander time Timing signal Significant instants

Doc. CX5012 v2.1 Page 2 of 15 © Calnex Solutions

1 Introduction to Clocks ............................................................................................................................... 3

1.1 What is a clock? ................................................................................................................................. 3

1.2 Timing Signals .................................................................................................................................... 3

1.3 Synchronisation Systems ................................................................................................................... 4

1.4 Clock Specifications ........................................................................................................................... 4

2 Packet-based Clocks .................................................................................................................................. 5

2.1 Packet Timing Signals ........................................................................................................................ 5

2.2 Two-way Timing Protocols ................................................................................................................ 6

2.3 Packet Timing Clocks ......................................................................................................................... 7

2.4 Packet Timing Systems ...................................................................................................................... 7

3 Boundary Clocks for Full Timing Support .................................................................................................. 8

3.1 Functional Model ............................................................................................................................... 8

3.2 Time Error Generation ....................................................................................................................... 9

3.3 Time Error Tolerance ....................................................................................................................... 10

3.4 Time Error Transfer.......................................................................................................................... 11

3.5 Short-term Transient Response ....................................................................................................... 12

3.6 Long-term Transient Response (Holdover) ..................................................................................... 13

4 Further Reading ....................................................................................................................................... 14

Doc. CX5012 v2.1 Page 3 of 15 © Calnex Solutions

Timing jitter and wander

time

Timing signal Significant instants

Doc. CX5012 v2.1 Page 4 of 15 © Calnex Solutions

PRC Up to 20 SECs* Up to 20 SECs* SSU SSU Up to 20 SECs* SSU

Up to 10 SSUs

End Equipment

* No more than 60 SECs allowed in any one chain

Doc. CX5012 v2.1 Page 5 of 15 © Calnex Solutions

F H H \ F Payload H F

Packet Delay Variation Event Packets (header, payload and footer)

Significant instants

time

F H H \ F Payload H F F H H \ F Payload H F F H H \ F Payload H F

Doc. CX5012 v2.1 Page 6 of 15 © Calnex Solutions

Slave Clock Time

Data at Slave Clock

DELAY_RESP message containing value of t4

SYNC message

DELAY_REQ message

time t1, t2, t3, t4

t1, t2

t1, t2, t3

t2

t3

t1

t4

Master Clock Time

Doc. CX5012 v2.1 Page 7 of 15 © Calnex Solutions

PTP GM PTP Slave

PTP GM PTP Slave

Full Timing Support (G.8275.1): every switch/router on the path between GM and slave contains a PTP Boundary Clock

Partial Timing Support (G.8275.2): not all switch/routers on the path between GM and slave contain a PTP Boundary Clock

switch/routers containing a PTP BC

ordinary switch/routers

Doc. CX5012 v2.1 Page 8 of 15 © Calnex Solutions

EEC

SyncE SyncE

1pps

PTP PTP

Slav

e

Mas

ter

Doc. CX5012 v2.1 Page 9 of 15 © Calnex Solutions

EEC

SyncE SyncE

1pps

PTP PTP

Slav

e

Mas

ter

Interval

Tim

e In

terv

al E

rro

r

“Ideal” Freq. Ref

Time

Tim

e Er

ror “Ideal” Time Ref

Time

Tim

e Er

ror “Noisy” output

Doc. CX5012 v2.1 Page 10 of 15 © Calnex Solutions

Figure 8: T-BC Time Error Tolerance

EEC

SyncE SyncE

1pps

PTP PTP

Slav

e

Mas

ter

Interval

Tim

e In

terv

al E

rro

r

“Noisy” Freq. Ref

Time

Tim

e Er

ror “Noisy” Time Ref

Time

Tim

e Er

ror “Noisy” output

MTIE

τ (s)

660ns

360ns

250ns

1µs

100ns0.01 0.0625 1 2.2 10 100 275 1000 100000.1

Doc. CX5012 v2.1 Page 11 of 15 © Calnex Solutions

0.05 0.1 Frequency, Hz

Amplitude, dB

Slope of 20dB/decade

Amplitude, dB

0.05 0.1 Frequency, Hz

Slopes of 20dB/decade

1 10

Doc. CX5012 v2.1 Page 12 of 15 © Calnex Solutions

EEC

SyncE SyncE

1pps

PTP PTP

Slav

e

Mas

ter

Interval

Tim

e In

terv

al E

rro

r

Sinusoidal Wander

Time

Tim

e Er

ror Sinusoidal Time Error

Time

Tim

e Er

ror Attenuated output

Doc. CX5012 v2.1 Page 13 of 15 © Calnex Solutions

T-BC output phase mask for first output phase error transient after start of SyncE rearrangement

Time after start of first output phase error transient (s)

0 5 10 15 20 25 30

Maxim

um

phase e

rror

(ns)

0

50

100

150

200

250

300

350

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