Multi-Lane Timestamping via Skew Compensation
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Solution Overview
Problem
Conventional time-stamping protocols, such as IEEE 1588-2008, are inadequate for determining the arrival time of data packets on multi-lane links due to skew between lanes, leading to incorrect timestamping where sequentially later packets may be given earlier timestamps than preceding packets.
Innovation Solution
A method and apparatus for determining packet arrival times on multi-lane links by calculating a predetermined function of word arrival times, including averaging or pro-rating based on lane number, to accurately account for skew and ensure consistent timestamping across lanes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional time-stamping protocols (IEEE 1588-2008) are used to determine packet arrival time, then the timestamping process is simple and straightforward, but the timestamp accuracy deteriorates due to lane skew causing sequentially later packets to receive earlier timestamps
Solution Approach 1:
The patent segments the packet arrival time determination into multiple components: individual lane arrival time detection for each lane, skew measurement for each lane, and a processing stage that combines these measurements. This segmentation allows accurate compensation for lane skew while maintaining a structured approach to the timestamping process.
Solution Approach 2:
The patent introduces intermediary elements including skew measurement circuits that measure the skew between lanes, FIFO buffers that compensate for timing differences, and processing logic that acts as a mediator between individual lane arrival times and the final packet timestamp. These intermediaries enable accurate timestamping despite lane skew variations.
2Productivity
If data is striped across multiple lanes to increase bandwidth, then the data transfer capacity increases, but lane skew causes arrival time determination to become inaccurate
Solution Approach 1:
The patent changes the parameters used for arrival time determination by incorporating lane-specific skew measurements and arrival time offsets. Instead of using a single reference point, the system adjusts timing parameters for each lane based on measured skew, enabling accurate packet arrival time determination even when data is striped across multiple lanes with different propagation delays.
Data Source
AI summary
One embodiment relates to a method of determining an arrival time of a data packet which has data striped across a plurality of lanes of a multi-lane link. Word arrival times for a subset of the words of the data packet are determined, each word arrival time corresponding to an arrival time of a word of the data packet at an individual lane of the multi-lane link. The arrival time of the data packet is determined using the word arrival times for the subset of words. Another embodiment relates to a method of determining an arrival time of a data packet which uses a measure of average fullness for a set of the FIFO buffers. Other embodiments and features are also disclosed.