This document discusses software synchronization techniques for cloud and telecom applications. It outlines trends driving more software-based synchronization, including miniaturization, consolidation, and scalability. It then examines the Time Appliance Project (TAP) and Open RAN architectures as examples where software synchronization could provide accurate timing to virtualized applications over standard server hardware. Specific techniques presented include using a software PTP client called SoftSync, hardware timestamping NICs, and precision time measurement over PCIe to synchronize virtualized applications with sub-microsecond accuracy. The document concludes that while dedicated hardware provides the highest accuracy for critical applications, software synchronization is suitable today for applications like TAP and O-RAN using standard servers, and precision time measurement over

1. Building on TAP
Ken Hann; WSTS 2023; Vancouver
Sync resiliency for the cloud

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• Data centre / general trends
• Motivation for synchronization with software
• Time Appliance Project
• O-RAN architecture
• Software synchronization and the virtual measurement
• Options; results; interfaces;
Agenda

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New role of software in synchronization
Miniaturization
Consolidation
General trends Cloud trends
Scalability Explosive growth
(Synchronization management)
Sustainability Open source (white box)
(Efficiencies of scale)
Accuracy;
resiliency;
security

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Clocks - hardware with “soul”
PPS or PTP
• HW timestamping of events
• Accuracy HW (~1ns)
• Accuracy SW (~1us)
• Huge vendor investment
• (ORAN; TAP;
Interface(s)
CPU
Application
(SW)
HW
Clock
(PHC)
(RTC/PLL)
OS
Application
(SW)
`
...
...

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Existing clocks/applications use dedicated HW
Synchronization network management
Optical Cs ePRC+
NG GM/SSU
Magnetic PRC/ePRC
Access Edge Core
NG GM/SSU
Device/network
monitor
Front/backhaul
Core network
O-RAN/edge DC
TV
studio
Defense
comm
Aviation
radars
Data
center
Financial
trading
911 center
Smart power
grids
HP Optical Cs
Cesium

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For distribution
or
local application?
Software synchronization

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Data centers - open time server
= TimeCard + standard server + standard NIC
• Interconnect via PCIe (using PTM)
• Optional PPS connections (pre-PTM)
TAP use case:

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M.2 slot is commonly available and allows smooth sync add on
OSA PCIe TimeCard with M.2 module as core
Core built as M.2
Sync Module
Concept Implementation
PCIe x
1
PCIe x1 (x2; x4)
SGMII x2

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O-RU BASED ON WHITEBOX SERVER + NIC + ACCELERATOR
High-accuracy sync over PCIe
Telecoms - Open-RAN architecture

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HOW?
Software synchronization

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Whitebox server with SoftSync
OSCILLOQUARTZ SOLUTION
• HW timestamping NIC (Intel)
• SoftSync PTP client on host machine
• Synchronizes OS with system APIs
• Performance ~ 100ns (timestamping NIC)
Interface(s) NIC
CPU
Software
app
1
SoftSync
OS
Software
app
2
PPS or PTP
`

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SoftSync measurement using G.8265.1 master
Back to back

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White box server with PCIe / M.2 interface
• GNSS input
• Local Ethernet port (PTP)
• No offset between GNSS and Ethernet
• PCIe port
Interface PCIe
CPU
Software
app
1
OS
Software
app
2
GNSS
Local
Ethernet

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PRECISION TIME MEASUREMENT
Synchronization over PCI-e (PTM)

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Whitebox server with PCIe / M.2 interface
PTM ON PCIE TO IMPROVE PERFORMANCE
• PTM support on PCIe
• PCIe <-> CPU ~10ns
• CPU <-> OS ~ 1ns
• No offset between GNSS and Ethernet (PTP)
• Class C BC possible
• PTM becoming available
PCIe
CPU
Software
app
1
OS
Software
app
2
GNSS
Local
Ethernet
PTM

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SYNCHRONIZATION OF VIRTUALIZED APPLICATIONS E.G. O-RAN
What other applications?
Infrastructure synchronized by SW
PCIe
CPU
Application
2
O-RU
PCIe
CPU
Application
1
O-DU
Ethernet Ethernet
PTM
PTM
PTP
TGPI
O
TGPI
O

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Conclusions
1) Highest accuracy applications requires dedicated HW
2) Sync on COTs server (TAP; O-RAN)
• Available today ~100ns (e.g SoftSync)
• PTM enables ~10ns accuracy (also for virtualized sw)
• PCIe = Timing interface
3) M.2 Sync Module = small footprint PCI-e

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