Packet Switching Device Ring Topology Real-Time Ethernet
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Solution Overview
Problem
Current Ethernet networks lack real-time functionality, particularly in industrial applications, due to the CSMA/CD access method and complex cabling requirements, which hinder reliable transmission of Ethernet telegrams at short cycle times, making them unsuitable for real-time control tasks.
Innovation Solution
A packet switching device with a network interface, string interfaces, and a switching unit that uses an interface association table to forward data packets independently of their addresses, allowing for mandatory output of network interface data packets to string interfaces and vice versa, and connects participants via a ring-shaped transmission path to minimize delays and ensure real-time processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the CSMA/CD access method is used in Ethernet networks, then standard hardware and software components can be utilized with high data transmission rates, but real-time functionality is lost due to unpredictable transmission delays under strong network load
Solution Approach 1:
The network traffic is segmented into different priority levels. Critical real-time telegrams are separated from regular traffic and handled with highest priority, ensuring predictable transmission times while maintaining high overall network throughput through multi-level queuing mechanisms
Solution Approach 2:
The transmission parameters are dynamically adjusted based on traffic type. Real-time telegrams receive fixed transmission slots with guaranteed bandwidth, while regular traffic adapts to available capacity, transforming the network from a purely contention-based system to one with reserved resources for time-critical applications
2Reliability
If a star topology with point-to-point connections is used to achieve real-time functionality, then fixed reaction times can be guaranteed, but complex cabling and high costs are required
Solution Approach 1:
The network switch is designed to handle multiple traffic types simultaneously - real-time telegrams, isochronous data, and regular Ethernet traffic - all over the same physical infrastructure. This multi-functionality eliminates the need for separate dedicated cabling for real-time applications while maintaining guaranteed transmission times through priority-based scheduling
Solution Approach 2:
The network dynamically allocates transmission resources based on traffic requirements. Time-critical telegrams receive immediate transmission slots regardless of network load, while regular traffic is scheduled in available gaps, allowing the system to adapt to varying real-time demands without changing the physical topology
3Ease of operation
If address comparison is performed for each data packet in the switch, then correct routing can be ensured, but transmission delays increase and real-time processing is hindered
Solution Approach 1:
The switch performs preliminary classification of incoming telegrams based on priority markers before full address comparison. High-priority real-time telegrams are identified and routed through fast paths with minimal processing, while regular traffic undergoes complete address lookup, reducing average transmission delays without compromising routing accuracy
Data Source
AI summary
A packet switching device comprises a network interface configured to send and receive data packets via a communication network, a plurality of string interfaces configured to transmit and receive data packets to/from a plurality of participants and a switching unit connected to the network interface and to the plurality of string interfaces. The a switching unit comprises a control unit configured to control a data throughput. The control unit comprises an interface association table which determines that data packets received via the network interface are mandatorily outputted via the string interfaces and the data packets received via the string interfaces are mandatorily outputted via the network interface.