Ethernet on the Floor

InTech, Nov 2006 by Fondl, Mark

EthernetIP

EthernetIP utilizes the services and features of the TCP/IP protocol to transport implicit and explicit messages over Ethernet. When referring to Ethernet in ControlNet messaging, it is the same standard Ethernet as described in the IEEE 802.3 specification.

It is not a proprietary version. TCP/IP allows a node to encapsulate ControlNet message in the data field of an Ethernet frame and then send the data to an Ethernet chip instead of the ASIC chip used in ControlNet. By utilizing UDP/IP, implicit messaging can occur, as there is no protocol information, only real-time I/O data. The data undergoes definition at connection time. These messages are small, low overhead messages and are critical for the performance needed for real-time control.

Network management

As Ethernet and TCP/IP become more and more prevalent on the factory floor, there is a growing need to maintain devices and their configurations and optimize the network. Network management is becoming more and more critical to automation. Intelligent devices are cropping up at lower levels on the factory floor.

Network management usually involves a distributed database, polling of devices, generating real-time graphical views of network topology changes, and traffic patterns. As companies realize the cost benefits and productivity gains created by network technology, they begin to add networks and expand existing networks almost as rapidly as new network technologies. The problems associated with network expansion affect day-to-day network operation management and strategic network growth planning.

Each new network technology requires specific expertise.

There are different areas of network management. They are: configuration, accounting, fault, security, and performance. Each has its own goals and specifics. Performance management relates to the various aspects of network performance, so users can maintain internetworking performance at an acceptable level. Configuration management involves monitoring and system configuration information, so users can track and manage the operation of various versions of hardware and software elements. Accounting management measures network utilization parameters, so they can properly regulate individual or group uses on the network. Fault management detects, logs, and notifies users of problems. Security management controls access to network information as designated by guidelines. This is done through Simple Network Management Protocol (SNMP).

A network management system contains two elements-a manager and agents. The manager is typically the PC through which the network administrator performs network management functions and is the network management station (NMS). Agents are the entities that interface to the actual device being managed. Bridges, hubs, routers, or servers are examples of managed devices that contain managed objects. These managed objects might be hardware, configuration parameters, performance statistics, and so on, that directly relate to the current operation of the device in question, These objects go in a virtual database, called a management information base (MIB). MIBs define the properties of the managed object within the device.