Double Sliding Window Packet Search for Link Trace Delay
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Solution Overview
Problem
High-speed interconnection interfaces in high-end server systems face stability and efficiency issues due to transmission differences caused by trace delay and inconsistency in multi-channel transmission, requiring a method to manage and match packet transmission characteristics with specific links.
Innovation Solution
The implementation of a packet search method using double sliding windows, where a first-level sliding window is positioned based on primary testing to center the packet data, and a second-level sliding window dynamically adjusts the packet position within a 32-bit offset, ensuring reliable and stable transmission by matching transmission characteristics with each link.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single sliding window is used for packet search, then the device complexity is low, but the transmission stability and consistency across multi-channel links deteriorates due to trace delay variations
Solution Approach 1:
The single sliding window is divided into two hierarchical levels: a first-level sliding window that provides coarse positioning with a larger search range to accommodate trace delay variations across different links, and a second-level sliding window that performs fine-grained packet search within a 32-bit offset range. This segmentation allows each window to operate at its optimal resolution, improving transmission stability while maintaining manageable device complexity through modular design.
Solution Approach 2:
The system implements dynamic adjustment of the second-level sliding window position based on the output from the first-level window. The first-level window dynamically determines the base position, and the second-level window dynamically searches within the offset range around this base position. This dynamic two-stage adjustment mechanism adapts to varying trace delays on different links, ensuring stable transmission across multi-channel interfaces.
2Adaptability or versatility
If the sliding window position is fixed, then the device complexity is low, but the adaptability to different transmission links with varying trace delays deteriorates
Solution Approach 1:
The system transforms the fixed sliding window into a dynamic two-level structure. The first-level sliding window is positioned based on primary testing results and provides adaptability to different links by accommodating trace delay variations. The second-level sliding window dynamically adjusts within a 32-bit offset range to precisely locate packet data. This dynamic positioning mechanism enables the system to adapt to various transmission link characteristics without requiring complete redesign for each link.
Solution Approach 2:
The system performs preliminary testing on each transmission link to determine the optimal position of the first-level sliding window before actual packet transmission. This preliminary characterization of trace delay properties allows the system to pre-position the first-level window appropriately for each link, reducing the search burden on the second-level window and improving overall adaptability while managing complexity through advance preparation.
3Adaptability or versatility
If a large search range is used to accommodate trace delay variations, then the adaptability to different links is improved, but the packet search time increases
Solution Approach 1:
The search range is segmented into two hierarchical levels: the first-level sliding window covers a large search range to accommodate trace delay variations across different links, while the second-level sliding window performs a limited search within a 32-bit offset range around the first-level window's position. This segmentation reduces the total search time by dividing the large search space into a coarse search phase and a fine search phase, maintaining adaptability while minimizing packet search time.
Solution Approach 2:
The two-level sliding window system dynamically coordinates the search process: the first-level window establishes a base position based on the large search range, and the second-level window dynamically searches within the offset range around this base. This dynamic coordinated search reduces the effective search time compared to a single large-scale search, as the second-level window only needs to search within a limited 32-bit offset rather than the entire large range.
Data Source
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Figure 3
AI summary
A method of implementing packet search by double sliding windows is provided. The method adopts a three-level barrel shift register to store input packet data, and a position of a sliding window 1 is determined at 32 positions by primary testing of a link, so as to ensure that the packet data is located at the center of the sliding window 1, thereby ensuring that the position of the sliding window 1 meets a transmission characteristic of a specific link to the maximum extent. After the position of the sliding window 1 is determined, 32-bit packet data can be effectively searched in the sliding window 1 by dynamically adjusting a sliding window 2, and 32-bit transmission offset is allowed for the packet data. The method of implementing packet search by double sliding windows meets a transmission characteristic of a specific link to the maximum extent.