Multi-plane cell switch fabric asynchronous reordering
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Solution Overview
Problem
Conventional multi-plane cell switches face challenges in maintaining high switching capacity while preventing the lowering of switching capacity due to distributing and restoring processings, and in restoring the original order of cells arriving in random order from multiple switches with a smaller hardware scale.
Innovation Solution
The solution involves dividing variable length data into fixed length data, distributing them evenly across multiple switching units, and using a reordering unit that compares sequence numbers to restore the original order of packets, thereby reducing hardware requirements and maintaining high switching capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If cells are distributed to multiple asynchronous switching units for high switching capacity, then switching capacity is improved, but cells arrive in random order requiring complex reordering hardware
Solution Approach 1:
The patent applies preliminary action by attaching sequence numbers to cells at the distribution unit before they enter the switching fabric. This pre-marking allows receiving units to identify and reorder cells without complex hardware, as the sorting information is prepared in advance during distribution.
Solution Approach 2:
The patent introduces sequence numbers as an intermediary element that mediates between the distributed asynchronous switching units and the reordering process. These sequence numbers serve as a simple tagging mechanism that enables efficient cell reordering without requiring complex synchronization or buffering hardware.
2Ease of operation
If synchronous switching units are used to maintain cell order, then packet restoration is simplified, but switching capacity and speed are reduced
Solution Approach 1:
The patent segments the switching function into multiple independent asynchronous switching units, each capable of operating at high speed without synchronization constraints. This segmentation allows parallel processing and high switching capacity while the sequence number mechanism handles ordering independently.
Solution Approach 2:
The patent replaces the mechanical synchronization system (which would require all switching units to operate in lockstep) with a logical ordering system based on sequence numbers. This substitution allows asynchronous operation and high switching capacity while maintaining packet integrity through software-based reordering.
3Speed
If high speed SerDes transmission is used to improve switch LSI speed, then switching speed is improved, but complete synchronization between switches becomes impossible
Solution Approach 1:
The patent embraces dynamics by designing the system to operate asynchronously rather than requiring static synchronization. The sequence number mechanism dynamically adapts to varying transmission speeds and timing differences between high-speed SerDes links, allowing each switching unit to operate independently at optimal speed.
Data Source
AI summary
Disclosed herewith is a multi-plane cell switch fabric system in which each switching unit functions asynchronously with others. The system executes distribution/restoration operations without lowering the switching capacity to reorder cells that arrive in random order from a plurality of switches just as they were in original flows and packets respectively with a small hardware capacity. In the system, the distribution unit divides each variable length packet addressed to the same destination into fixed length cells and sends those divided cells by a unit of integer multiple of the number of switches. On the other hand, the reordering unit, while holding cells that arrive in random order from each switching unit (switching units 1 to M) in a receive buffer, separates only the header information from each cell and holds the header information in a retry queue. The reordering unit, upon finding the header information of a head cell of a flow in an ordering check at the time of receiving or in a retry check in the retry queue, extracts the corresponding cell bodies from the receive buffer to restore the original order of those cells in the subject packet.