In-band PTP Timestamp Signaling for Master Entity Processing
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Solution Overview
Problem
In Precision Time Protocol (PTP) systems, achieving high precision timing synchronization across distributed networks, such as Ethernet networks, is challenging due to latency and jitter issues. Current methods, like using dedicated links or increasing synchronization message rates, either incur significant costs or increase processing loads on master entities.
Innovation Solution
Implementing in-band signaling to communicate timestamp information from the kernel space to the user space within the PTP master entity, allowing for the capture, modification, and extraction of timing information within the same message, thereby reducing the need for context switches and preventing timestamp queue overflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If out-of-band signaling is used to obtain T4 timestamps for each PTP Delay Request message, then timing precision can be maintained, but processing load on the master entity increases significantly
Solution Approach 1:
The patent combines the timestamp capture function with the PTP message processing function by implementing in-band signaling. The T4 timestamp is captured and embedded directly within the PTP Delay Response message itself, eliminating the need for separate out-of-band signaling operations. This merging of functions reduces context switches between kernel and user space, thereby reducing processing load while maintaining timing precision.
Solution Approach 2:
The patent introduces an intermediary mechanism where the kernel space captures the T4 timestamp and places it in a timestamp queue, which then serves as an intermediate data structure that the user space PTP application can access without requiring context switches for each timestamp retrieval. This intermediary queue decouples the timestamp capture from the message processing, reducing processing load.
2Measurement precision
If the message rate is increased to achieve better synchronization accuracy, then timing precision improves, but processing load on the master entity increases
Solution Approach 1:
The patent performs preliminary action by capturing the T4 timestamp in the kernel space at the moment the PTP Delay Request message is received, before the message is processed by the user space application. This preliminary capture eliminates the need for repeated context switches during message processing, allowing the system to handle higher message rates without proportionally increasing processing load.
3Productivity
If a timestamp queue is implemented to store T4 timestamps, then timing information can be retrieved efficiently, but the queue may overflow under high message rates
Solution Approach 1:
The patent extracts the T4 timestamp from the kernel space and embeds it directly into the PTP Delay Response message in the user space. By taking out the timestamp from the kernel's internal queue mechanism and incorporating it into the message payload, the system eliminates the timestamp queue entirely, preventing overflow while maintaining efficient retrieval.
Data Source
AI summary
One embodiment is directed to a technique for in-band signaling of time stamp information where a kernel driver executing in kernel space modifies a received timing message (for example, a Precision Time Protocol (PTP) Delay Request message) to include timing information associated with the time the timing message was received by a network interface. This is done so that an application running in the user space can obtain the timing information from the modified timing message and reconstruct a timestamp for the received timing message (for example, a PTP T4 timestamp) for use in implementing at least a part of a packet-based synchronization protocol (for example, the PTP).