eDCN, enhanced distributed communications network
The basic structure of the eDCN on an Advant MOD 300 Software is an ethernet based bus with subnetworks connected to it. The eDCN has been designed using models and standards set by the ISO and IEEE. The eDCN is capable of connecting to existing DCN installations and other networks as well as encompassing future developments in networking standards. This allows the matching of capabilities and costs with the control and information requirements of process plants.
The eDCN is the communications medium which allows the functional and geographical
The eDCN is made of up communications devices called nodes, and communication paths between the nodes called links. The bus topology permits effective implementation of critical network control strategies. To avoid the overhead associated with lots of collisions in a traditional “shared” Ethernet network, the eDCN uses a “switched” Ethernet technology that limits the collision domain to each node and a switch.
The eDCN is a bus network by which messages travel from node, to switch, to node. Physically,it is a twisted pair 10Base-T cable interconnecting the nodes to switches that can be linked together in a “backbone” using 10Base-T or 100Base-X copper wire or fiber optics media. The dual eDCNs function simultaneously and provide parallel communications paths for data travelling through the system. The use of this dual network improves average response time by as much as 50%. In addition, it provides a high degree of security, as a failure of one of the networks causes the remaining one to automatically assume full service. distribution of these subsystems.
Multiple Network Domain Topology
The ability to interconnect two or more eDCN network domains makes it practical to have very large systems. Because the multiple network domain structure does not imply any hierarchy (that is, no one domain has higher communication priority than any other), the choice of how many domains to use and which nodes should reside on each may be made on virtually any logical basis, such as:
• Geographic (various plant or process areas)
• Functional (groups of similar processes, unit train operations)
• Control system geographics (control room and process)
• System performance (localize high density traffic to improve access or response time)
• Fault tolerance (segment to localize fault impact)
This high degree of flexibility is possible due to the nature of the communications system. No matter how the domains are interconnected, the entire network appears to the users and APs as a single logical network.