Preemptive Packet Transmission for Low Latency
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Solution Overview
Problem
Existing network queuing and scheduling algorithms fail to minimize latency for high-priority frames effectively, leading to increased latency and fragmentation of lower priority flows, especially in networks requiring low latency and accurate timestamping, and are not compatible with all network layers.
Innovation Solution
Configuring network devices to support preemptive priorities, where higher priority frames can interrupt and restart the transmission of lower priority frames, ensuring minimal latency and accurate timestamping by designating critical flows with preemptive rights over non-critical flows, and implementing an algorithm that transmits an invalid frame check sequence to manage frame transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If existing network queuing and scheduling algorithms are used, then network device complexity is reduced, but latency for high-priority frames increases and timestamping accuracy deteriorates
Solution Approach 1:
The patent segments the frame transmission process into multiple parts by introducing a frame check sequence (FCS) that can be independently validated. When a high-priority frame arrives during low-priority frame transmission, the low-priority frame is suspended and resumed later, with FCS validation ensuring data integrity across the segmentation boundary. This allows priority-based preemption without compromising reliability.
Solution Approach 2:
The patent performs preliminary actions by pre-configuring preemptive priority rights among different frame priorities and pre-calculating FCS values before transmission. When preemption is needed, the system can immediately suspend the current frame and switch to the high-priority frame without complex real-time decision-making, reducing latency while maintaining manageable device complexity.
2Loss of time
If preemptive priority transmission is implemented, then latency for high-priority frames is minimized, but fragmentation of lower priority flows increases
Solution Approach 1:
The patent applies beforehand cushioning by implementing FCS validation and frame reassembly mechanisms that cushion against the disruptive effects of preemption. When a low-priority frame is suspended, the FCS stored beforehand allows the frame to be correctly reassembled and validated after resumption, maintaining flow stability despite fragmentation caused by high-priority preemptions.
3Measurement precision
If preemptive priorities are configured, then timestamping accuracy is maintained, but device complexity increases
Solution Approach 1:
The patent extracts the timestamping function as a separate, dedicated mechanism that operates independently from the priority scheduling logic. By extracting timestamp recording to a specific hardware component or dedicated software module, the system maintains precise timestamping for high-priority frames without requiring the entire device architecture to be complex, as only the timestamping subsystem needs to be simple and dedicated.
Data Source
AI summary
Disclosed herein is technology to reduce latency of frames through a network device supporting various priorities. In an implementation, a method comprises configuring one or more priorities with a preemptive right over other one or more of said plurality of priorities; receiving frames in a sequence, each of the frames having a frame priority comprising of one of said plurality of priorities; queuing the received frames in a predetermined order based on a frame arrival time and the frame priority; transmitting a current frame based on a current frame priority and current frame arrival time; stopping transmission of the current frame when a later frame in the sequence is received that has a later frame priority with preemptive right over the current frame priority; transmitting an invalid frame check sequence; transmitting the later frame; and restarting the transmission of the current frame after transmitting the later frame.