AFDX Switch Rate Control via Silent Periods
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Solution Overview
Problem
Avionics Full-Duplex Switched Ethernet (AFDX) networks face challenges with low capacity end systems that cannot process data frames as fast as they arrive, leading to inefficiencies and increased costs, especially with higher line rate capabilities like 1 Gbps and 10 Gbps, as software-based end systems struggle to manage bursts of data.
Innovation Solution
The implementation of a star topology data network with packet schedulers and effective line rate utilization mechanisms that introduce silent periods after frame transmission, allowing switches to manage data flow asynchronously and reduce the transmission rate to a configured effective rate, enabling low capacity end systems to connect to high capacity physical lines without requiring additional processing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high capacity physical lines (1 Gbps and 10 Gbps) are used in AFDX networks, then bandwidth and data transfer capability are improved, but low capacity end systems cannot process data frames as fast as they arrive, leading to inefficiencies and increased costs
Solution Approach 1:
The switch dynamically adjusts the transmission rate on a per-flow basis by introducing variable-length silent periods between frame transmissions. This allows the system to adapt the effective transmission rate to match the receiving capability of low capacity end systems while utilizing high capacity physical lines, thereby resolving the contradiction between high bandwidth capability and data processing efficiency.
Solution Approach 2:
The invention changes the transmission rate parameter by introducing silent periods that vary in length based on the configured effective rate. This parameter adjustment enables the system to operate at different effective rates on the same physical line, allowing high capacity lines to serve low capacity end systems without loss of efficiency or increase in cost.
2Reliability
If synchronous scheduling is implemented for proper AFDX operation, then deterministic Quality of Service is maintained, but device complexity and cost increase due to coordinated clock timing requirements
Solution Approach 1:
The invention segments the transmission control into independent per-flow silent period mechanisms rather than requiring global synchronous scheduling. Each flow can be managed independently with its own silent periods, eliminating the need for complex coordinated clock timing while maintaining deterministic QoS through configurable effective rates.
Solution Approach 2:
The invention extracts the timing coordination requirement from the overall system operation by introducing silent periods that are configured independently at each switch. This removes the need for synchronous scheduling and coordinated clock timing while preserving the deterministic QoS characteristics through flow-specific rate control.
3Productivity
If end systems operate at line rate, then data processing capability is maximized, but software-based end systems struggle to manage bursts of data, increasing system cost
Solution Approach 1:
The invention applies partial action by having the physical line transmit at full capacity while the effective rate is reduced through silent periods to match the end system's processing capability. This allows the system to maximize physical throughput while preventing buffer overflow at low capacity end systems, eliminating the need for expensive high processing capacity software-based end systems.
Data Source
AI summary
A data network includes a plurality of end systems; a plurality of line data buses connected to the end systems; and a plurality of switches connected to the line data buses and to other switches via trunk data buses to define a star topology. The switches and end systems are configured to operate asynchronously. Each switch includes a number of packet schedulers for managing the transmission of received data flow. A number of effective line rate utilization mechanisms are each associated with a respective packet scheduler for providing the service rate of that packet scheduler. Switch egress ports transmit the received data flow. Each switch egress port has a defined configured effective transmission rate. Each effective line rate utilization mechanism reduces the utilization rate to the defined configured effective transmission rate.