Fibre Channel Switch Timeout Checker Circuit
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Solution Overview
Problem
Fibre channel switch elements lack the ability to track the time frames have taken to traverse the fabric, leading to congestion and frame latency due to stalled frames, which degrades network performance.
Innovation Solution
Incorporating a time stamp value in fibre channel frames and using a timeout checker circuit to determine if a frame has timed out by comparing the time stamp with a programmed timeout value and global counter value, allowing for the declaration of major or minor timeouts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fibre channel switch elements do not track frame transit time, then the system is simpler to implement, but congestion and frame latency increase due to stalled frames
Solution Approach 1:
The patent applies preliminary action by inserting a time stamp value into the frame header at the moment the frame enters the switch element. This time stamp is programmed in advance as a reference point, allowing the exit processor to later calculate the transit time by comparing the current time with the recorded time stamp, thereby enabling frame tracking without complex continuous monitoring mechanisms.
Solution Approach 2:
The patent replaces complex mechanical time-tracking mechanisms with a simpler temporal comparison system. Instead of using sophisticated hardware timers or continuous counters to track frame transit time, the invention uses a time stamp value stored in the frame header and compares it with the current time at the exit processor, substituting complex tracking hardware with a simpler software-based time comparison approach.
2Device complexity
If frames are not processed with timeout declaration, then frame processing is simpler, but congestion increases due to stalled frames
Solution Approach 1:
The patent implements feedback by having the exit processor compare the current time with the time stamp value to determine if a timeout has occurred. This feedback mechanism allows the system to detect when a frame has been stalled too long and take appropriate action, such as discarding the frame or generating an error signal, thereby preventing congestion without requiring complex continuous monitoring at every switch element.
Solution Approach 2:
The patent extracts the timeout determination function from the frame processing logic at individual switch elements and consolidates it at the exit processor. By removing the timeout checking complexity from intermediate switch elements and placing it only at the exit point, the system reduces overall processing complexity while still effectively managing congestion through timeout-based frame handling.
3Measurement precision
If time stamp values are inserted in frames, then frame transit time can be tracked, but frame overhead increases
Solution Approach 1:
The patent applies parameter changes by utilizing existing frame header fields to store the time stamp value. Instead of adding a completely new data structure or increasing frame size significantly, the invention repurposes available header parameters to accommodate the time stamp, thereby achieving precise transit time measurement with minimal impact on frame data volume and structure.
Data Source
AI summary
Method and system for routing fiber channel frames using a fiber channel switch element is provided. The method includes, inserting a time stamp value in a fiber channel frame that is received at a receive segment of the fiber channel switch element; determining if a timeout occurs after a frame arrives at a receive buffer; and processing the frame if the timeout occurred. The method also includes, determining if a delta time value, which provides an accumulated wait time for a frame, is present in frame data; subtracting the delta time stamp value from a global time stamp value and using the resulting time stamp value to determine frame timeout status in the fiber channel switch element. A timeout checker circuit declares a timeout after comparing a time stamp value that is inserted in a fiber channel frame with a programmed time out value and global counter value.