OPC-UA Multicast Subscription for Server Network Load Reduction
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Solution Overview
Problem
In OPC-UA networks, multiple clients interested in the same server information establish bilateral communication channels, leading to inefficient data access and increased server and network utilization, as each client requests the same values independently.
Innovation Solution
Implementing a method where clients register for server services using a subscription structure with a unique multicast group, allowing the server to transmit value changes to all registered clients via a single multicast message, reducing the need for individual polled refresh requests and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If each client establishes bilateral communication with the server and requests values independently, then each client can access the server service, but the server and network utilization increases due to multiple separate communication channels and repeated requests for the same data
Solution Approach 1:
The patent merges multiple separate communication channels into a single multicast group. Instead of each client establishing individual bilateral communication with the server, all clients subscribe to a shared multicast group where the server publishes data once and all clients receive it simultaneously. This combining of communication paths directly reduces server processing load and network traffic while maintaining client access capability.
2Reliability
If the server transmits separate messages to each registered client, then each client receives value changes, but the network traffic and server workload increase with the number of clients
Solution Approach 1:
The patent combines multiple individual message transmissions into a single multicast message. The server publishes value changes to a shared multicast group instead of sending separate messages to each client. This single publication action reliably delivers notifications to all subscribed clients simultaneously, maintaining reliability while dramatically improving subscription efficiency by reducing server workload and network traffic proportional to the number of clients.
3Adaptability or versatility
If multiple HMI devices show the same view of server state, then comprehensive monitoring is achieved, but redundant communication channels consume excessive network resources
Solution Approach 1:
The patent creates a universal multicast group that serves multiple HMI devices simultaneously. Instead of dedicating separate communication channels to each HMI device, a single multicast group provides universal access to the same server state information for all clients. This multi-functional approach allows any number of HMI devices to monitor the server state through one shared communication path, achieving comprehensive monitoring while eliminating redundant network resource consumption.
Data Source
AI summary
A method for providing clients with access to a service of a server in a network using an OPC-UA, the server service making available varying values of at least one variable to the clients, wherein a client registers for the server service by sending a subscription request for the server service to the server which sets up a subscription structure including a unique subscription ID as well as a TCP/IP multicast group associated with the subscription structure and including a unique multicast address, and there server communicates the multicast address and the subscription ID to every client submitting a subscription request to register for the server service, the server additionally sends each change in value of each variable of the server service to the multicast address over a network via a multicast message so that all clients registered for the server service receive the same multicast message.