Adjusting Information Unit Pacing Credit to Reduce Latency
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Solution Overview
Problem
The default information unit pacing credit in Fibre Channel standards limits data transmission rates at higher link speeds and longer distances, introducing latency due to the need for frequent handshakes and resource constraints.
Innovation Solution
Increasing the information unit pacing credit beyond the default value of 16 to allow more information units to be transmitted without intermediate handshakes, with the option to adjust based on workload and resource availability, and implementing persistent pacing across logical paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the default information unit pacing credit value of 16 is used, then resource constraints are managed, but data transmission rate is limited at higher link speeds and longer distances
Solution Approach 1:
The patent implements dynamic adjustment of the information unit pacing credit parameter, allowing it to be modified based on workload conditions and resource availability. The system can increase the pacing credit beyond the default value of 16 when resources are available and workload demands higher transmission rates, and decrease it when resources are constrained, thereby optimizing both throughput and latency adaptively
Solution Approach 2:
The patent directly modifies the information unit pacing credit parameter value to resolve the contradiction. By changing this parameter from the fixed default of 16 to adjustable values (increasing when needed for higher transmission rates, decreasing when resources are constrained), the system achieves both improved productivity and reduced latency under appropriate conditions
2Productivity
If the information unit pacing credit is increased to allow more information units to be sent without handshakes, then data transmission efficiency is enhanced, but resource overburdening may occur
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors resource availability and workload conditions, then adjusts the information unit pacing credit accordingly. This feedback loop ensures that the pacing credit is increased only when resources can handle the additional load, preventing resource overburdening while maximizing transmission efficiency when conditions permit
Solution Approach 2:
The system dynamically adjusts the pacing credit based on real-time resource conditions rather than using a fixed value. This dynamic adaptation allows the system to increase pacing credit for higher efficiency when resources are abundant, while automatically reducing it when resources are constrained, thereby maintaining reliability
3Reliability
If frequent handshakes are performed to manage pacing, then resource constraints are controlled, but transmission latency increases
Solution Approach 1:
The patent changes the pacing credit parameter value to reduce the frequency of handshakes. By increasing this parameter, larger batches of information units can be transmitted before requiring acknowledgment, thereby reducing the number of handshake cycles and the associated latency while still maintaining resource constraint management
Data Source
AI summary
A first device determines whether an indicator is configured to allow use of an increased value for an information unit pacing credit that is greater than a default value for the information unit pacing credit, where the information unit pacing credit indicates a number of information units that a second device is allowed to send to the first device without waiting for any additional response from the first device. In response to determining that the indicator is configured to allow use of the increased value for the information unit pacing credit that is greater than the default value for the information unit pacing credit, the first device adjusts the information unit pacing credit via a response sent from the first device to the second device, to the increased value that is greater than the default value.