Clock Synchronization in Aggregated Packet Networks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing packet-switched networks with aggregated connections, comprising multiple links, face challenges in accurately synchronizing slave clocks with master clocks due to link time asymmetry, which becomes significant at synchronization accuracy requirements below microsecond levels, and existing timestamp protocols only measure round-trip transmission times, not single-direction times.
Innovation Solution
A method and system that record and transmit specific information about the distribution of synchronization packets across links, using timestamps and packet transmission times to accurately determine single-direction transmission times, allowing for precise synchronization of master and slave clocks by calculating time offsets based on packet distribution and transmission times across multiple links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aggregated connections with multiple links are used between master and slave clocks, then network redundancy and efficiency are improved, but synchronization accuracy deteriorates due to link time asymmetry
Solution Approach 1:
The patent segments the aggregated connection into individual links and measures the transmission time for each link separately. By dividing the multi-link aggregated connection into discrete measurable segments, the system can accurately determine the transmission time contribution of each link, thereby resolving the time asymmetry problem while maintaining the redundancy benefits of aggregated connections.
Solution Approach 2:
The patent performs preliminary measurement of transmission times for each link in the aggregated connection before using them for synchronization calculations. By pre-measuring and storing the transmission time characteristics of each link, the system eliminates the need for real-time approximation during synchronization, thereby achieving microsecond or better accuracy while maintaining aggregated connection redundancy.
2Device complexity
If round-trip transmission time measurement is used, then device complexity is reduced, but synchronization accuracy deteriorates because single-direction transmission times cannot be determined
Solution Approach 1:
The patent introduces dynamic measurement capability that can adaptively measure transmission times in different directions (outbound and inbound) for each link. This dynamic approach allows the system to capture the actual asymmetric transmission characteristics rather than relying on static round-trip averages, thereby achieving accurate single-direction time determination without excessive complexity.
Solution Approach 2:
The patent uses transparent clocks positioned at intermediate nodes in the network path as mediators to measure and report transmission times for each link. These intermediary devices break down the complex end-to-end measurement problem into manageable per-link measurements, enabling accurate single-direction time determination while distributing the measurement complexity across multiple simple intermediary devices rather than requiring complex functionality at the endpoint clocks.
Data Source
AI summary
An exemplary technique is provided for synchronizing master and slave clocks of a packet-switched network. The network contains at least two equipments that are connected to one another via an aggregated connection made up of at least two links and that are located between the master and slave clocks to enable them to transmit synchronization packets to one another using a timestamp protocol. The technique includes (a) obtaining a distribution of the synchronization packets in at least one subset of the links that transport these synchronization packets, and (b) transmitting to the slave clock first information representative of that distribution, second information representative of timestamps associated with the synchronization packets, and third information representative of packet transmission times over the at least one subset of links, to synchronize the slave clock to the master clock as a function of at least the first, second, and third information transmitted.