Shared NIC Hardware Clock for Multi-Host Time Synchronization
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Solution Overview
Problem
Achieving precise clock synchronization across network nodes is challenging due to latency and jitter in distributing clock synchronization messages, and existing solutions like PTP require hardware-based time stamping and are costly for high-speed networks, while providing a scalable solution is difficult with multiple hardware clocks.
Innovation Solution
A network interface card device with a single hardware clock that is disciplined by a designated controlling device, allowing non-controlling devices to communicate as if they are disciplining the clock without actual updates, using a clock controller to select and re-designate controlling devices based on various criteria, and storing offsets for time zone adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single hardware clock is shared among multiple hosts, then cost is reduced and scalability is improved, but clock synchronization precision deteriorates due to latency and jitter in message distribution
Solution Approach 1:
The patent introduces a boundary clock device as an intermediary between the external PTP master and multiple internal hosts. This boundary clock receives synchronization messages from the external master and distributes them to multiple hosts, acting as a mediator that eliminates the need for direct peer-to-peer synchronization between each host and the external master, thereby reducing latency and jitter while maintaining synchronization precision.
Solution Approach 2:
The system segments the clock synchronization function by separating the boundary clock role from the host clock roles. The boundary clock handles external communication and message distribution, while each host maintains its own hardware clock for local timekeeping. This segmentation allows the single boundary clock to serve multiple hosts without compromising individual host synchronization precision.
2Measurement precision
If multiple hardware clocks are provided for each host, then clock synchronization precision is improved, but device complexity and cost increase
Solution Approach 1:
The boundary clock device performs multiple functions: it acts as a PTP slave to the external master, serves as a PTP master to multiple internal hosts, and functions as a message distribution hub. This multi-functionality eliminates the need for each host to independently implement complex PTP slave functionality, reducing overall device complexity while maintaining synchronization precision through the boundary clock's dedicated hardware clock.
3Productivity
If protocol offloading is implemented in NIC to reduce host processing burden, then productivity is improved, but NIC cost and complexity increase substantially
Solution Approach 1:
The patent extracts the clock synchronization processing function from the NIC and places it in the host CPU. Instead of implementing complex PTP synchronization logic in the NIC hardware, the host CPU runs a PTP client that communicates with the boundary clock through simple get/set time messages. This extraction reduces NIC complexity while maintaining high processing efficiency by utilizing the host's existing CPU resources.
Data Source
AI summary
In one embodiment, a network interface card device includes communication interfaces to provide data connection with respective local devices configured to run respective clock synchronization clients, at least one network interface to provide data connection between a packet data network and ones of the local devices, and a hardware clock to maintain a time value, and serve the clock synchronization clients.