NTP Server Timestamp Precision via Hardware Clock Extraction
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Solution Overview
Problem
Existing Network Time Protocol (NTP) servers introduce inaccuracies in timestamping due to delays and uncertainties from software layers, leading to errors in clock synchronization across data networks.
Innovation Solution
A method that requests current time from a hardware clock and a correction term from a latency estimator filter to insert precise transmit timestamps into outgoing packets, updating the correction term based on the offset between calculated and actual time-of-departure, ensuring accurate timestamping without disrupting compatibility with current NTP standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If NTP servers use software layers (device drivers, network stacks, operating systems) to process and timestamp packets, then the system is easier to operate and maintain, but timestamp accuracy deteriorates due to processing delays and uncertainties
Solution Approach 1:
The patent extracts the timestamping function from the software processing chain and places it at the physical layer boundary. The NTP server records timestamps at the moment packets cross the physical layer interface, before they enter software layers for processing. This separation eliminates the uncertainty introduced by software processing while maintaining system ease of operation.
Solution Approach 2:
The patent performs timestamping in advance, at the physical layer boundary before packets are processed by software layers. By recording the timestamp at the moment packets cross the physical interface, the system captures the true arrival/departure time without waiting for software processing to complete, thereby eliminating processing delay uncertainty.
2Ease of manufacture
If NTP servers record timestamps after packets traverse software layers, then the timestamping process is simpler to implement, but the timestamps become inaccurate due to random processing delays
Solution Approach 1:
The patent extracts the timestamping operation from the software processing sequence and positions it at the physical layer boundary. This requires minimal additional hardware or firmware capability and can be implemented by most modern network interfaces, while dramatically improving timestamp accuracy by eliminating software processing delays.
Solution Approach 2:
The patent introduces an intermediary timestamping mechanism at the physical layer boundary that acts as a mediator between the network interface and software layers. This intermediary records the true crossing time of packets without being affected by software processing delays, providing accurate timestamps while maintaining compatibility with existing software architectures.
3Measurement precision
If NTP servers use hardware-based clocks with external standards, then time-keeping accuracy is improved, but errors are introduced by inaccuracies in the timestamping function within the server
Solution Approach 1:
The patent extracts the timestamping function from the software processing chain and places it at the physical layer boundary, where it can operate independently of software inaccuracies. This ensures that even with highly accurate hardware clocks, the timestamping process itself does not introduce errors, thereby maintaining both time-keeping accuracy and reliability.
Solution Approach 2:
The patent implements a feedback mechanism where the NTP server continuously monitors and adjusts for any discrepancies between the hardware clock and the actual packet crossing times recorded at the physical layer boundary. This feedback loop compensates for any drift or inaccuracies, ensuring both high time-keeping accuracy and reliability.
Data Source
AI summary
Embodiments of the present invention set forth a method and system for reducing uncertainty in receive and transmit timestamps created by an NTP server. The uncertainty in the receive timestamps is removed by recording the time-of-arrival in the hardware clock of the NTP server before the incoming packets may be delayed by traversing the various layers of software in a timestamping system. The uncertainty in the transmit timestamps is removed by giving the outgoing packets a timestamp in the future using an estimate of the transmission latency calculated by the latency estimator filter. Subsequently, the actual time-of-departure is used to re-calculate and update the estimate of the transmission latency. In this fashion, superior control of the timestamping function may be implemented in existing NTP servers in a manner that retains interworking compatibility with the current NTP standards.