Relay Device Fixed Delay Queue for Network Frame Jitter
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Solution Overview
Problem
Existing relay devices in general-purpose networks face challenges in preventing delay jitter for high-priority frames due to conflicts with low-priority frames, and existing solutions either require dedicated devices or cannot ensure minimum delay jitter.
Innovation Solution
A relay device with a determination unit to classify frames, a high-priority queue that delays high-priority frames by a fixed time, and a low-priority frame storing unit that stores and retransmits low-priority frames, ensuring a fixed delay and minimizing delay jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If store-and-forward transfer method with Priority Queuing is used, then transfer delay time of high-priority frames is reduced, but delay jitter cannot be eliminated due to transfer conflicts at output ports
Solution Approach 1:
The patent segments the transfer process into two distinct phases: a first transfer period where high-priority frames are transferred with highest priority, and a second transfer period where low-priority frames are transferred. This temporal segmentation eliminates transfer conflicts at the output port by ensuring that high-priority and low-priority frames are never transferred simultaneously, thereby resolving the delay jitter problem while maintaining reduced transfer delay times.
2Loss of time
If high-priority frames are transferred preferentially during transmission of low-priority frames, then transfer delay is reduced, but delay jitter occurs due to waiting for low-priority frame transmission to complete
Solution Approach 1:
The patent implements periodic action by dividing the transfer operation into distinct periodic phases: a first transfer period dedicated to high-priority frame transfer, followed by a second transfer period for low-priority frame transfer. This periodic structure ensures that high-priority frames are always transferred during their designated period without being blocked by low-priority frames, eliminating delay jitter while maintaining efficient transfer timing.
3Reliability
If dedicated devices are used to prevent delay jitter, then delay jitter is eliminated, but device complexity and cost increase
Solution Approach 1:
The patent applies dynamics by making the transfer priorities dynamic rather than static. The relay device dynamically switches between two transfer modes: during the first transfer period, high-priority frames are transferred with highest priority; during the second transfer period, low-priority frames are transferred. This dynamic priority switching within a single device achieves delay jitter prevention without requiring multiple dedicated devices, thereby reducing device complexity while maintaining reliability.
Data Source
AI summary
The relay device includes: a frame determination unit that determines a received frame between a high-priority frame and a low-priority frame for each output port on a basis of an identifier; a fixed-delay queue that delays the high-priority frame for a time equal to or longer than the sum of a specified transmission gap and a frame length long enough for a downstream device to be capable of correctly receiving and transferring or discarding a frame, and that transmits the high-priority frame; a low-priority frame storing unit that stores therein the low-priority frame; a transmission-frame selection unit that executes control to discontinue transmission of the low-priority frame when transmitting the high-priority frame, and to retransmit the low-priority frame; and an output control unit that selects a frame to be transmitted to the downstream device on a basis of the control by the transmission-frame selection unit.