Packet Timing System Using TTL for Hop Count
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Solution Overview
Problem
Timing synchronization in communication networks is adversely affected by unpredictable changes in packet flight time due to network congestion, which existing protocols like PTP struggle to accurately account for, leading to suboptimal synchronization performance.
Innovation Solution
The implementation of a modified Best Master Clock Algorithm (BMCA) that utilizes the Time to Live (TTL) field of IP packets to determine the number of network elements in the path to each grandmaster clock, allowing for more accurate selection of the best timing source, irrespective of whether network elements are PTP-aware or not, thereby minimizing packet delay variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PTP protocol is used for timing synchronization, then timing precision can reach nanosecond level, but synchronization performance deteriorates due to unpredictable packet flight time changes from network congestion
Solution Approach 1:
The patent pre-calculates and stores expected packet flight times for different hop counts before synchronization operations occur. When selecting a master clock, the system retrieves pre-computed flight time values based on the TTL field, avoiding real-time measurement uncertainties and enabling more reliable synchronization decisions even under network congestion conditions.
Solution Approach 2:
The patent introduces the TTL (Time to Live) field as an intermediary parameter that indirectly indicates network path characteristics. Instead of directly measuring packet flight time which is affected by congestion, the system uses TTL as a mediator to estimate hop count and retrieve corresponding pre-stored flight time values, thereby decoupling synchronization accuracy from real-time network conditions.
2Ease of operation
If traditional BMCA is used to select master clock, then selection is based on limited parameters, but accuracy of timing synchronization deteriorates due to inability to account for network path variations
Solution Approach 1:
The patent enhances the traditional BMCA to serve multiple functions: it not only selects the best master clock based on timing quality but also determines optimal path characteristics using the TTL field. This multi-functional algorithm simultaneously optimizes both master clock selection and path selection, improving timing synchronization accuracy without adding separate complex selection mechanisms.
Solution Approach 2:
The patent modifies the BMCA by incorporating the TTL field as an additional selection parameter. The enhanced algorithm changes the selection criteria from traditional parameters alone to a combination of timing quality parameters and TTL-based hop count parameters, enabling more accurate master clock selection that accounts for network path variations.
3Device complexity
If packet flight time is assumed constant for synchronization, then protocol complexity is reduced, but synchronization accuracy deteriorates due to network congestion causing unpredictable flight time changes
Solution Approach 1:
The patent pre-calculates packet flight times for different hop count values and stores them in lookup tables before runtime. This preliminary action allows the system to use simple TTL-based indexing during operation while maintaining high synchronization accuracy, avoiding the need for complex real-time flight time calculations or constant protocol modifications.
Solution Approach 2:
The patent creates a simplified model of network behavior by copying expected flight time patterns into pre-computed lookup tables. Instead of dealing with the full complexity of real-time network variations, the system uses these copied patterns based on TTL values to estimate flight times, maintaining accuracy while keeping protocol complexity low.
Data Source
AI summary
Devices and methods that receive timing information from at least one source clock in a network that exchanges data packets conforming to the Internet Protocol. The timing information preferably includes a time-to-live (TTL) field in a packet header used to: select a source of timing information; configure a PTP port, or both.