Post on 12-Apr-2017
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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
PTPSlave 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
PTPSlave 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
LocalMacro Base Station
GNSS
T-SC
Core/Mobile Backhaul Provider
Mobile Network Operator
High PDV/ Asymmetry
Packet-Based Backhaul Network
PTPSlave Clock
Slave
Each network element needs to bePTP-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 supportSmall 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
LocalMacro Base Station
GNSS
T-SC
Core/Mobile Backhaul Provider
Mobile Network Operator
High PDV/ Asymmetry
Packet-Based Backhaul Network
PTPSlave 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 GMPTP TS &Probe
Clk+1pps
pps
Reference PRTC
GPS splitter
ppsTraffic 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%
800
400
TIE
(nsec)
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Test #1 – Probe Measured Forward Delay
• Window size – 5sec , Lucky packet
10%-100% 100%-10%
25265
TE(n
sec)
26505
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Test #1 – Probe Measured Reverse Delay
• Window size – 5sec , Lucky packet
10%-100% (Fr) 100%-10% (Fr)
25308
TE(n
sec)
25612
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Test #1 – Probe Measured Asymmetry
• Window size – 5sec , Lucky packet
10%-100% 100%-10%
-370
TE(n
sec)
296
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Test #1 – 1PPS TE (Tester)
• Time Error within +/- 150nsec – well within +/- 1100nsec
-15
01
00
TE (
nsec)
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Test #1 – 1PPS TE Probe Vs ref PRTC• Time Error within +/- 150nsec – well within +/- 1100nsec
-196
TE(n
sec)
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%
630
720
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 GMPTP TS &Probe
Clk+1pps
pps
Reference PRTC
GPS splitter
ppsTraffic 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%
2000
12000
TIE
(nsec)8000
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Test #3 – 1PPS TE (Tester)
• Time Error within +/- 250nsec – well within +/- 1100nsec
-60
240
TE(n
sec)
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 availableGPS
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)
Nlaufer@advaoptical.com
Questions? Thank you!
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