CQF Segmentation for Synchronized Time-Sensitive Packet Forwarding
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Solution Overview
Problem
Existing time-sensitive networking technologies face challenges in maintaining synchronization and precision timing across network nodes, leading to potential packet loss and excessive delays, especially as networks grow, due to the impracticality of syntonizing all nodes and the need for large buffer capacities and per-stream shapers.
Innovation Solution
The network is divided into CQF segments, where nodes within each segment operate on a synchronized clock, using cyclic flow meters and paternoster shapers to manage buffer swapping and stream bundling to ensure synchronized queuing and forwarding, while allowing different clock frequencies between segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all network nodes are syntonized to maintain synchronization and precision timing, then time-sensitive data transmission reliability is improved, but device complexity and operational difficulty increase significantly as networks grow
Solution Approach 1:
The network is divided into multiple CQF segments, where each segment maintains internal synchronization independently. Nodes within a segment are syntonized to a common clock frequency, but different segments can operate at different frequencies. This segmentation approach maintains time-sensitive data transmission reliability within each segment while significantly reducing the overall network synchronization complexity by avoiding the need to syntonize all nodes across the entire network.
2Reliability
If large buffer capacities are used to prevent packet loss during congestion, then data loss is reduced, but delay increases which is unacceptable for time-sensitive applications
Solution Approach 1:
The system uses periodic buffer swapping at synchronized time intervals within each CQF segment. Buffers are exchanged at regular cycles determined by the segment's clock frequency, which prevents congestion-induced packet loss while maintaining predictable, finite worst-case delivery times. This periodic action eliminates the need for large continuous buffers that would otherwise be required to handle congestion, thereby avoiding excessive buffering delays for time-sensitive packets.
3Reliability
If per-stream shapers are implemented to manage bandwidth allocation, then quality of service for time-sensitive streams is improved, but device complexity and resource requirements increase
Solution Approach 1:
Multiple time-sensitive streams are bundled together and treated as a single aggregate flow within each CQF segment. The cyclic flow meter applies a single shaping mechanism to the bundled streams collectively, rather than implementing separate per-stream shapers. This merging approach maintains quality of service guarantees for all bundled streams while significantly reducing device complexity and resource requirements by eliminating the need for individual per-stream shaping state and control logic.
4Reliability
If excessive buffering is used to handle congestion, then packet loss is prevented, but bandwidth utilization efficiency decreases
Solution Approach 1:
The system dynamically swaps buffers in a cyclic manner at synchronized intervals, allowing the same physical buffer resources to be reused for different streams at different times. This dynamic buffer management enables efficient bandwidth utilization by preventing permanent allocation of buffer space, while still providing reliable congestion handling through the periodic buffer exchange mechanism that ensures no packets are lost due to buffer overflow.
Data Source
AI summary
A method for communicating time sensitive data streams in a network. The method includes synchronizing queuing and transmission of data in a set of output buffers for buffering streams associated with a certain class of service. The method includes processing data packets of a stream using a cyclic flow meter, wherein the cyclic flow meter limits transfer of the data packets of the stream to the set of output buffers of the network node according to a predetermined amount per cycle based on an output frequency. The method includes transmitting, according to the output frequency, the data packets of the stream from a non-empty output buffer of the set of output buffers, and transferring the data packets of the stream from the cyclic flow meter to an empty output buffer of the set of output buffers.