Deterministic Latency in Packet Forwarding via Cycle Time Entries
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Solution Overview
Problem
Deterministic networking technologies, such as CQF, fail to accurately implement latency guarantees during packet forwarding due to link latency variations, leading to inaccurate maximum packet forwarding latency calculations.
Innovation Solution
A method that determines a forwarding path based on latency requirements, generates entries with cycle time correspondence for each network node, and sends packets at specific cycle times to ensure deterministic latency, using a controller to manage and coordinate packet forwarding across network nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If CQF technology is used to forward packets in cycle times, then packet forwarding can be simplified and basic latency bounds can be established, but link latency variations cause inaccurate maximum packet forwarding latency calculations and fail to provide accurate deterministic latency guarantees
Solution Approach 1:
The controller pre-calculates and determines the specific cycle time numbers for forwarding packets at each network node before actual packet transmission. This preliminary action accounts for link latencies and node processing latencies in advance, ensuring that packets are forwarded at precisely timed moments that guarantee the required latency bounds, thereby resolving the inaccuracy caused by link latency variations while maintaining the simplicity of CQF cycle-based forwarding
Solution Approach 2:
The system uses pre-calculated latency information (link latencies and node processing latencies) as feedback to adjust and determine the optimal cycle time numbers for packet forwarding. This feedback mechanism allows the controller to compensate for link latency variations by selecting appropriate cycle time numbers that ensure accurate deterministic latency guarantees, while the network nodes continue to operate with simple cycle-based forwarding logic
2Reliability
If the controller determines specific cycle time numbers for each network node based on latency requirements, then accurate deterministic latency guarantees can be achieved, but the system complexity increases due to coordinated management across multiple nodes
Solution Approach 1:
The controller performs multiple functions including determining forwarding paths, calculating latencies, and assigning cycle time numbers for all network nodes in a unified manner. This multi-functionality allows the system to achieve accurate deterministic latency guarantees through centralized coordination, while the network nodes themselves maintain simple cycle-based forwarding operations, effectively distributing the complexity management to the controller while keeping node operations universal and simple
3Manufacturing precision
If packets are sent at precise cycle time numbers determined by the controller, then deterministic latency requirements are met, but the flexibility in packet scheduling is reduced compared to traditional queue management
Solution Approach 1:
The system dynamically determines cycle time numbers based on specific packet characteristics including service flow requirements, latency bounds, link latencies, and node processing latencies. Rather than using fixed cycle-based forwarding for all packets, the controller adaptively assigns optimal cycle time numbers for each packet or flow, achieving precise packet sending time control while maintaining scheduling flexibility through dynamic parameter adjustment
Data Source
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AI summary
This application discloses a packet sending method, a network node, and a system. A controller obtains a forwarding latency requirement of a service flow and a destination address of the service flow, determines a forwarding path that meets the forwarding latency requirement, and determines a number of a first cycle time in which an ingress node on the forwarding path forwards a packet and a number of a second cycle time in which an intermediate node on the forwarding path forwards the packet. The controller sends a first entry to the ingress node. The first entry includes a sequence number of the packet and the first cycle time number, and the first entry is used to indicate the ingress node to send the packet in a time period corresponding to the first cycle time number. The controller sends a second entry to the intermediate node. The second entry includes the sequence number of the packet and the second cycle time number. The second entry is used to indicate the intermediate node to send the packet in a time period corresponding to the second cycle time number. In this solution, the ingress node and the intermediate node on the forwarding path separately forward the packet in a corresponding cycle time, to implement a deterministic latency guarantee during packet forwarding.