Switches are the communication experts in our networks, intelligently routing data to its destination across all communication levels, from Operational Technology (OT) and Industrial IT (IIT) to traditional IT. They play a crucial role in ensuring efficient and reliable data transmission within these systems. But how do they function, and what do they actually achieve? Let’s take a detailed look, starting at the OT level in the PROFIBUS field bus system.
Switches in the PROFIBUS Field Bus System
In the PROFIBUS field bus system, high-performance infrastructure components like switches are not required because master and slave devices communicate sequentially according to the question/answer principle. This setup can be likened to a one-way road where only one vehicle can travel in one direction at a time between the production plant and the supplier.
Ethernet-Based Systems: The Role of Switches
In Ethernet-based systems such as PROFINET, there is a two-way communication path. Data packets, or telegrams, not only run between the controller and devices or between the server and clients but also allow devices to communicate with each other by passing the controller. In these systems, switches are as crucial as traffic lights in road traffic. They manage data flow efficiently, ensuring that telegrams are received and sent through ports.
The Modern Switch: A Logistics Hub
Modern switches are comparable to logistics hubs. Just as packages are managed on a loading dock, telegrams are handled via ports on a switch. An 8-port switch, for instance, can create 8 different data connections to devices or other switches. The speed mode of each port—whether gigabits, 100 megabits, or 10 megabits—depends on factors such as the type of data cable, like cat5, cat6, ca7 (similar to the quality of a road) and the condition of the cable.
Full Duplex and Half Duplex Modes
In optimal conditions, switches operate in full duplex mode, allowing simultaneous sending and receiving of data. However, if issues arise on a data line, the switch may automatically switch to half duplex mode, which only supports sending or receiving data at a given time. This switch to half duplex can delay data processing significantly. Once the data line is fully functional again, the system reverts to the fastest possible transmission mode, a process known as auto-negotiation.
The Importance of Switch Memory
A switch’s memory is vital for handling incoming and outgoing data frames. The memory consists of input and output queues and a buffer for interim storage. When a data packet arrives, it is first placed in the input queue, checked for errors, and, if necessary, deleted. Next, it is sorted and temporarily stored in the buffer before being forwarded to the appropriate output queue based on the first-in-first-out principle.
Store-and-Forward vs. Cut-Through Modes
Switches typically operate in store-and-forward mode, where packets are checked for errors before being forwarded. However, cut-through switches can move packets directly from the input to the output queue without error checking, reducing processing time but increasing the risk of forwarding faulty packets. If the load on the output queue increases significantly, a cut-through switch will revert to store-and-forward mode to avoid data loss.
TSN and Dynamic Memory Management
With Time-Sensitive Networking (TSN), lead times are minimized, and a return to store-and-forward mode is no longer necessary as capacities are reserved in the queues. In dynamic mode, the memory of an underutilized output queue can be used for another output queue, ensuring efficient data handling.
Prioritization and Network Load Management
Modern switches have prioritization mechanisms to handle time-critical packets, such as PROFINET telegrams in OT or VoIP in IT, ensuring they are given priority in the network. Large, non-time-critical data packets must wait. A high-quality switch will have several output queues per port and significant memory space to manage this load effectively. They can withstand high network loads, and their performance is often defined by switching capacity, switching memory, and switching speed.
Handling Network Instabilities
In industrial environments, unwanted leakage currents (EMC influences) can strain data traffic. A good switch can withstand, monitor, and report rising loads from these influences. Managed switches are essential for recording operating parameters and making them available for external analysis, which helps prevent network breakdowns.
Advanced Features of Managed Switches
Managed switches offer features such as SNMP access, web interfaces, onboard network diagnostics, and mirror ports for telegram analysis. These features provide critical data for network monitoring and help maintain an up-to-date topology plan. They ensure that network maintenance is manageable and that the operation remains stable in the long term.
Conclusion
Switches are the backbone of modern network communication, ensuring data is routed efficiently and reliably across various systems. The switches series from Maisvch embody these advanced capabilities, making network management straightforward and operations stable over the long term. Choosing the right switch determines whether you have control over your network or whether your network has control over you. Invest in intelligent switch solutions to ensure your network’s optimal performance and stability.
