At ITSF 2020, Ken Hann explained the need to interconnect and share time between PTP equipment using different profiles. He outlined the cross-profile challenges and showed that a combination of multi-profile grandmaster technology and pluggable boundary clocks offers an ideal solution.

1. PTP across borders – Babel retold
Kenneth Hann, senior director, R&D, Oscilloquartz, ADVA
ITSF, Nov 2020

2. © 2020 ADVA. All rights reserved. Confidential.22
In the begining...
Clocks attempted time distribution to the heavens …
Each clock considered his protocol better than his fellows …
Then John said “since the industries cannot agree, we will grant them PTP profiles” …
(of PTP V2) ...

3. © 2020 ADVA. All rights reserved. Confidential.33
Motivation and background
• PTP profiles are many (even within the same industry)
• Profiles (by definition) cannot directly interoperate
At the same time ...
• Equipment requires concurrent support for multiple profiles
• Customer cases require conversion between profiles

4. © 2020 ADVA. All rights reserved. Confidential.44
Conversion between clocks and protocols
PTP – one protocol ”language” to represent time
Alternatives
Physical
clock
PPS SyncE 10MHz 2048kHz
Time
protocol
PTP NTP TOD (NMEA) IRIG-B
GNSS

5. Objective:
• Leverage PTP accuracy
• Protect investment with
existing NTP clients
Way forward:
• NTP/PTP gateway
• Enhancing NTP with
precise sync signal
(1PPS)
• Upgrading legacy
appliances with SFP GM
NTP migration – plug in accuracy
PTP to NTP conversion
Trade execution
NTP serverNTP client
NTP over
packet network
NTP
PTP
Migration
PTP slave
clock
NTP client
PTP grandmaster
synchronized from UTC
PTP over
packet network

6. © 2020 ADVA. All rights reserved. Confidential.66
Slaves must adhere to a profile
PTP – clocks divided by a common protocol
Alternatives
Transport L2 L3 L2 VLAN0 Other
Packet
forwarding
Multicast Unicast Mixed
multicast/unicast
Time
processing
BC E2E TC P2P TC None
Clock
hierarcy
BMCA
(dynamic)
BMCA’ (dynamic) BMCA’ (static)
Profile
”details”
Message rates Domain numbers Clock class values Etc.

7. © 2020 ADVA. All rights reserved. Confidential.77
How many PTP profiles?
https://sagroups.ieee.org/1588/ptp-profiles/
Profile Profile ID Main features
”Telecoms 2008” 00-1B-19-00-01-00 L3; based on default L3 profile
Telecoms G.8265.1 00-19-A7-00-01-00 L3; frequency only; high packet rates
Telecoms G.8275.1 00-19-A7-01-01-00 L2; full timing support from the network
Telecoms G.8275.2 00-19-A7-02-01-00 L3; partial timing support from the network
Enterprise 00-00-5E-00-01-00 L3; mixed multicast / unicast
IEEE Std 802.1AS 00-80-C2-00-01-00 L2; multicast; peer-peer
SMPTE Profile (2059-2) 68-97-E8-00-01-00 L3; multicast
AES67 00-0B-5E-00-01-00 L3; multicast
Power 1 (C37.238-2011) 1C-12-9D-00-00-00 L2; VLAN 0; multicast; peer-peer
Power 2 (C37.238.2017) 1C-12-9D-00-00-00 L2; VLAN 0; multicast; peer-peer
Power 3 (61850-9-3) 00-0C-CD-00-01-x0 L2; multicast; peer-peer

8. © 2020 ADVA. All rights reserved. Confidential.88
Identifying profiles – on the wire
A bit more challenging
Bits Octets
7 6 5 4 3 2 1 0
clockType 2
physicalLayerProtocol L
physicalAddressLength 2
physicalAddress S
protocolAddress N
manufacturerIdentity 3
Reserved 1
productDescription P
revisionData Q
userDescription R
profileIdentity 6
Pad M
CLOCK DESCRIPTION TLV
• Uniquely identifies profile using profileID
But …
• PTP management TLV
• Not supported by most profiles
Profiles are usually configured per (virtual) port

9. © 2020 ADVA. All rights reserved. Confidential.99
Supporting multiple applications/profiles
PTP
G.8265.1
PTP/NTP
enterprise
PTP
G.8275.2
PTP
G.8275.1
2G/3G/4G/
5G FDD BS
DOCSIS 3.1
and small cells
and APTS
MIFID ii
5G/LTE
TDD/LTE-A BS
and small cells
PTP Power
61850-9-3/
C37.238
Power utilities
PTP
broadcast
Studio

10. © 2020 ADVA. All rights reserved. Confidential.1010
Master may support multiple PTP profiles
But ...
M A M B
S BS A
S A S B
M A; B
1) Slaves can’t request a
specific profile
2) Networks may limit
profile connectivity

11. © 2020 ADVA. All rights reserved. Confidential.1111
Boundary clock function is needed for profile conversion
PHY
MAC
IP
PTP
G.8275.2
PHY
MAC
Physical clock
PTP
G.8275.1
BC as PTP profile convertor
Slave
Master
Master Slave

12. ITU telecom to power profile conversion
PTP
Telecom Profile
G.8265.1
G.8275.1
Event
recorder
IRIG B
Protection schemes
Remote
terminal
unit (RTU)
IRIG-B bus
1PPS
ADM
DS1/E1
G.703
9/13
GNSS
primary
Protection
relay
PMU
Alarm
annunciator
Substation
gateway
QOS
meter
Substation
switch
61850 LAN
 PTP
IEEE C37.118
 NTP
RELAY ROOM Core PTP GM
PTP
secondary
Cesium clock
Telecom core

13. M A
S A S B
Supporting multiple profiles (even on same physical port)
Add BC (or GM + APTS)
With no loss in accuracy
M A
S A S B
BC A->B
BC A->B
TC A; B

14. © 2020 ADVA. All rights reserved. Confidential.1414
Real world application - broadcast studio
GM SMPTE S G.8275.1
TC G.8275.1; SMPTE
TC SMPTE
S SMPTE
1. GNSS as a primary reference
2. PTP as a backup (G.8275.1) – no VLAN
3. GM – SMPTE, with one VLAN
GM G.8275.1
Adding multiple profile support with a plug

15. © 2020 ADVA. All rights reserved. Confidential.1515
Conclusions
1) The PTP Babel problem:
• So many profiles ...
• Increasingly interconnected
2) Practical solutions:
• Multi-profile capable GMs
• TC is enabler for multi-profile networks
• Pluggable devices can retrofit profile translation

16. Thank you
Questions?