Modicon M340 Plc Page 4-8 Services

4/8 Topologies (continued) Technical information Ethernet network Infrastructure Different network topologies (continued) Daisy chain topology (continued) Limitations of the daisy chain: Limitations of the daisy chain topology in terms of operational integrity of the network and performance metrics are as follows: b Dual port Ethernet devices only support 10 Mbps and/or 100 Mbps operational speeds and must use one or the other. b The network will operate only as fast as the slowest device that is connected to the network. b In order to improve network traffic latency, the number of devices in a single scan chain is limited to 32 devices. This means that the time for a round trip of a packet through the daisy chain is likely to be less than 5 milliseconds. The maximum latency of a packet passing through any device in a scan chain is no more than 10 s. Ring topology In a ring topology, all devices or network infrastructure components are connected in a loop. Through this type of topology, a type of network redundancy is achieved. Ring topologies also help improve the availability of the network and its communication to devices. Ethernet ring Ethernet rings are usually the backbones of applications in which high availability is required. If ring topology is required then switches that support this feature should be ordered. Deploying ring topologies using ConneXium ConneXium offers switches that allow the deployment of single and coupled self-healing rings. Daisy chain loop A daisy chain loop consists of several daisy chain devices that are placed in a ring topology. When an Ethernet network forms a loop, all the devices in that loop must use the same protocol (RSTP, MRP, or HIPER-Ring). DTE DTE DTE DTE 2 1 3 4 5 6 7 8 9 10 2 1 3 4 5 6 7 8 9 10

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