PTP-NTP Clock Synchronization for Cross-Network Shared Experiences

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Solution Overview

Problem

Existing synchronization techniques fail to achieve consistent synchronization accuracy across computing devices operating within local and wide area networks, leading to potential disruptions in shared experiences due to discontinuities and user discomfort.

Innovation Solution

A multi-protocol synchronization system utilizing both precise time protocol (PTP) and imprecise time protocol (NTP) to synchronize local devices and a global reference clock, with smearing techniques to smooth time adjustments, ensuring synchronized shared experiences across different networks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If PTP is used to synchronize local devices, then local synchronization accuracy is improved, but global synchronization consistency deteriorates

Engineering Contradiction:
Improvelocal synchronization accuracyVSAvoidglobal synchronization consistency
Core Design Contradiction:
Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent segments the synchronization system into two distinct protocols: PTP for local high-precision synchronization and NTP for global consistency. This segmentation allows each protocol to optimize for its specific function without interfering with the other, resolving the contradiction between local precision and global consistency.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces NTP as an intermediary protocol that bridges the gap between PTP-based local clocks and global timekeeping. NTP acts as a mediator that receives time information from multiple PTP-synced devices and distributes it globally, ensuring consistency across the entire network while preserving local precision.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Measurement precision

If frequent time adjustments are made to maintain synchronization, then synchronization accuracy is improved, but user experience deteriorates due to perceptible distortions

Engineering Contradiction:
Improvesynchronization accuracyVSAvoidperceptible distortions
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent implements periodic time adjustments rather than continuous corrections. By synchronizing at discrete intervals using NTP, the system maintains accuracy without creating continuous perceptible distortions. The periodic nature of the adjustments allows the system to correct drift while keeping changes imperceptible to users.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent changes the parameter of adjustment frequency and magnitude to balance accuracy with user experience. By using NTP for global synchronization, the system makes smaller, less frequent adjustments compared to pure PTP, reducing the likelihood of perceptible distortions while maintaining sufficient accuracy for most applications.

Inventive Principle:
Principle #35Parameter changes

3Device complexity

If a single synchronization protocol is used for all devices, then system complexity is reduced, but synchronization accuracy across diverse networks deteriorates

Engineering Contradiction:
Improvesystem complexityVSAvoidsynchronization accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent creates a universal synchronization architecture where both PTP and NTP protocols coexist and serve different functions. PTP handles local high-precision needs while NTP provides global coordination, making the system universally applicable across diverse network configurations without requiring a single complex protocol for all scenarios.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent applies local quality by allowing different synchronization behaviors at different levels of the network hierarchy. Local devices use PTP for high-precision synchronization, while global devices use NTP for consistency. This differentiated approach optimizes accuracy for each local network while maintaining overall system simplicity.

Inventive Principle:
Principle #3Local quality

Data Source

PatentEP4217826B1Multi-protocol synchronization
Publication Date: 2025.09.17 APPLE INC
  • EP4217826B1 patent drawingFigure 1
  • EP4217826B1 patent drawingFigure 2
  • EP4217826B1 patent drawingFigure 3A~3C

AI summary

Techniques are disclosed relating to maintaining a first reference clock for a first local area network (LAN). The first reference clock is usable by a first set of computing devices coupled to the first LAN to participate in a shared experience with a second set of computing devices coupled to a second LAN. A computing system synchronizes, via a first time synchronization protocol, the first reference clock with a global reference clock accessible to the computing system over a wide area network (WAN). The computing system provides, via a second time synchronization protocol, a time value of the first reference clock to one of the first set of computing devices to coordinate an event in the shared experience with one of the second set of computing devices, where the second time synchronization protocol has a precision that is greater than a precision of the first time synchronization protocol.