The document discusses challenges related to phase delivery in existing brownfield network deployments, highlighting issues such as asymmetry and packet delay variation (PDV). It presents solutions for improving phase delivery, specifically proposing to position the grand master closer to slave devices and utilizing various standards such as G.8275.1 and G.8275.2 for effective last-mile delivery. Additionally, the document emphasizes the importance of conducting sync surveys and utilizing quality of service (QoS) measures to mitigate PDV and asymmetry in network elements unaware of Precision Time Protocol (PTP).

1. Nir Laufer , Director Product Line Management
ITSF 2015
Phase Delivery over PTP Unaware Networks

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Phase Delivery Challenges in Brownfield Deployments
• Existing network introduce high level of asymmetry and PDV
• The asymmetry and PDV varies over time
• Existing networks include different transport technologies
• Upgrading/forklifting the existing NE to Sync-E/BC is very costly
Do we really need frequency and phase in the core network?

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Bypass the problem:
Get the Grand Master closer to the Slave
Core/Mobile
Backhaul
Provider
Mobile
Network
Operator
High PDV/
Asymmetry
PTP
Slave Clock
Slave
4G Base Station /
Small Cell
Grand
Master
GNSS
The Solution

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Grand
Master
GNSS
Core/Mobile
Backhaul
Provider
Mobile
Network
Operator
High PDV/
Asymmetry
PTP
Slave Clock
Slave
4G Base Station /
Small Cell
Packet-Based
Backhaul Network
Grand
Master
GNSS
Bypass the problem:
Get the Grand Master closer to the Slave
The Solution

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Phase Delivery:
Small Scale GM & G.8275.1 – Last Mile
• G.8275.1 – Uses hop by hop , Ethernet multicast
mini-GM
Local
Macro Base Station
GNSS
T-SC
Core/Mobile
Backhaul
Provider
Mobile
Network
Operator
High PDV/
Asymmetry
Packet-Based Backhaul Network
PTP
Slave Clock
Slave
Each network element needs to be
PTP-aware (T-BC) with Sync-E
BC
& Sync-E
BC
& Sync-E
BC
& Sync-E 4G Base Station /
Small Cell
16ppb & +/-1.1us
Ethernet Multicast
G.8275.1
Last mile full on path support
Small Scale GM as a head of G.8275.1 chain

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Phase Delivery:
Small Scale GM & G.8275.2 – Last Mile
• G.8275.2 – Uses IP unicast for phase delivery over last mile
mini-GM
Local
Macro Base Station
GNSS
T-SC
Core/Mobile
Backhaul
Provider
Mobile
Network
Operator
High PDV/
Asymmetry
Packet-Based Backhaul Network
PTP
Slave Clock
Slave
4G Base Station /
Small Cell
16ppb & +/-1.1us
G.8275.2
Small Scale GM as a head of G.8275.2 chain
? Slave
Slave

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PDV of a single NE
• Single congestion point
Two types of traffic loads have been considered:
• Case A: The size of the data traffic packets was variable,
from 64 bytes to 1518 bytes
• Case B: All the data traffic packets have a 1518 bytes fixed
size
Source - France Télécom Orange

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PDV of a single NE – Case A
1Gbps, variable size data traffic:
Source - France Télécom Orange

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PDV of a single NE – Case B
1Gbps, 1518 bytes data traffic:
:
Source - France Télécom Orange

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Setup #1
Tester
Traffic Analyzer
DUT #1 DUT #2
PTP flow
Disturbance traffic
PTP GM
PTP TS &
Probe
Clk+1pps
pps
Reference PRTC
GPS splitter
pps
Traffic Generator
Congestion point

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Test 1: G.8261 Traffic model #1
• Single Congestion , VLAN Priority
• PTP - 64 packets per second (on both directions)
• Single congestion point (on forward)
• Forward load traffic (no load on reverse direction)
• 80% -minimum size packets (64 octets)
• 15% - maximum size packets (1518 octets)
• 5% - medium size packets (576 octets)

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Test #1 - Forward & Reverse Filtered Packet TIE (Tester)
• Window size – 200 sec , 0.3%
100%
90%
80%70%60%50%40%30%20%10%
800400TIE(nsec)

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Test #1 – Probe Measured Forward Delay
• Window size – 5sec , Lucky packet
10%-100% 100%-10%
25265
TE(nsec)
26505

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Test #1 – Probe Measured Reverse Delay
• Window size – 5sec , Lucky packet
10%-100% (Fr) 100%-10% (Fr)
25308TE(nsec)25612

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Test #1 – Probe Measured Asymmetry
• Window size – 5sec , Lucky packet
10%-100% 100%-10%
-370
TE(nsec)
296

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Test #1 – 1PPS TE (Tester)
• Time Error within +/- 150nsec – well within +/- 1100nsec
-150
100
TE(nsec)

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Test #1 – 1PPS TE Probe Vs ref PRTC
• Time Error within +/- 150nsec – well within +/- 1100nsec
-196
TE(nsec)
56

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Test #1 – 1PPS MTIE (Tester)
• MTIE well under G.8271.1 network limits mask

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Test #1 – 1PPS MTIE Probe Vs Ref PRTC
• MTIE well under G.823 pdh mask

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• Single Congestion , VLAN Priority
• PTP - 64 packets per second (on both directions)
• Single congestion point (on forward)
• Forward load traffic (no load on reverse direction)
• 30% -minimum size packets (64 octets)
• 60% - maximum size packets (1518 octets)
• 10% - medium size packets (576 octets)
Test 2: G.8261 Traffic model #2

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Test #2 - Forward & Reverse Filtered Packet TIE (Tester)
• Window size – 200 sec , 0.3%
100%
90%
80%70%60%50%40%30%20%10%
630720
TIE(nsec)
360

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Test #2 – 1PPS TE (Tester)
• Time Error within +/- 200nsec – well within +/- 1100nsec
60
TE(nsec)-180

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Test #2 – 1PPS MTIE (Tester)
• MTIE well under G.8271.1 network limits mask

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Setup #2
Tester
Traffic Analyzer
DUT #1 DUT #2
PTP flow
Disturbance traffic
PTP GM
PTP TS &
Probe
Clk+1pps
pps
Reference PRTC
GPS splitter
pps
Traffic Generator
Congestion point
DUT #3

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Test 3: G.8261 Traffic model #1
• Two Congestion points , VLAN Priority
• PTP - 64 packets per second (on both directions)
• Single congestion point (on forward)
• Forward load traffic (no load on reverse direction)
• 60% -minimum size packets (64 octets)
• 15% - maximum size packets (1518 octets)
• 5% - medium size packets (576 octets)

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Test #3 - Forward & Reverse Filtered Packet TIE (Tester)
• Window size – 200 sec , 0.3%
100%
90%
80%70%60%50%40%30%20%10%
200012000
TIE(nsec)
8000

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Test #3 – 1PPS TE (Tester)
• Time Error within +/- 250nsec – well within +/- 1100nsec
-60
240
TE(nsec)
6000

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Test #3 – 1PPS MTIE (Tester)
• MTIE well under G.8271.1 network limits mask

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Other Access Technologies
• WDM/GPON/DSLAM/MW tend to include high level of PDV & Asymmetry
• In most cases would require on path support (BC/TC) in order to deliver accurate
phase
• Highly dependent on the vendor implementation – Sync Survey is recommended
mini-GM
GNSS
Core/Mobile
Backhaul
Provider
Mobile
Network
Operator
High PDV/
Asymmetry
Slave
MW+TC
Slave
Slave
BC/TC

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GPON
• GPON G.984.3 include mechanism for Time of Day distribution over G-PON –
interworking with PTP is still being developed but some proprietary solutions are
already proposed
• Very accurate phase delivery can be achieved
mini-GM
GNSS
Slave
Probe
Time Error
below 500 nsec
GNSS

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Microwave
• Highly dependent on the MW implementation
• PTP should be assigned to the highest QoS flow – can help reduce asymmetry and
PDV caused by adaptive modulation
• Proprietary BC/TC implementations are available
GPS
Transport unit Transport unit
PTP Slave &
Probe
Grand Master
GPS
Network asymmetry of 14usec over single MW hop
Vendor A

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Microwave –Cont
GPS
Transport unit Transport unit
PTP Slave &
Probe
Grand Master
GPS
Vendor B
Slave recovered clock within +/-250nsec

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Phase Delivery over PTP unaware networks
• Phase delivery over PTP unaware network elements is possible with the
following network engineering guidelines:
• Conduct Sync Survey - Test your access network elements PDV and
asymmetry under realistic load scenario
• Use QoS to prioritize PTP packets
• Avoid speed mismatch (or compensate for known asymmetry
generated by the mismatch)
• Avoid network traffic utilization above 90%
• If needed , use PTP aware network element for access technologies
(MW/WDM/DSLAM/GPON)

34. Nlaufer@advaoptical.com
Questions? Thank you!
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