Using Ethernet To Network, Topology And Redundancy

USING ETHERNET TO NETWORK

There are many ways Ethernet components and standards can be employed to provide redundancy, robustness, security, and flexibility of design for many industrial networks. As has already been mentioned, Ethernet is also the best integration strategy available to network planners and architects.

TOPOLOGY AND REDUNDANCY

Ethernet works with star, bus, mesh, and ring topologies insuring the right topology for the job is selected. At the edges of a network with geographically separated devices the ring topology supported by Ethernet managed switches provides several advantages. Ethernet switches that support IEEE 802.1w, the Rapid Spanning Tree Protocol (RSTP), provide redundant links that can quickly recover from topology changes and add to the reliability of the ring. Because RSTP is designed to work with all topologies, some vendors offer proprietary and/or standards-based redundancy protocols that can significantly reduce recovery time down to as little as 50ms in the simple rings that are often used at the edge of a network.

Since the ring is comprised of devices with point-to-point links, signal reshaping and re- transmission of the sending leg reduce the possibility of transmission errors. Cabling costs are also significantly reduced from installing a separate link to each remote device as in a star or mesh topology. Where all devices are co-located a simple star or bus topology can be employed.

Some Ethernet switches support dual-homing. In Ethernet LANs, dual-homing is a network topology that adds reliability by allowing a device to be connected to the network by way of two independent connection points (points of attachment). One connection point is the operating connection, and the other is a standby or back-up connection that is activated in the event of a failure of the operating connection.

All media types from coax and copper to fiber are supported by Ethernet, often as plug-in modules for hubs and switches. Bandwidth to the Gigabit range is available in several combinations.

SECURITY

The 2003 Slammer worm attack on portions of the Northeast U.S. power grid confirmed the need for better security than currently implemented. The Energy Policy Act of 2005, which goes into effect the summer of 2006, provided a further push for a higher level of security in power systems. Both Ethernet and TCP/IP provide several sophisticated security features honed in IT departments and equally available to industrial Ethernet users.

Several TCP/IP-based and IEEE-based standards have been updated or created to handle intrusions over Internet-like connections. These include various forms of user authentication, password protection, and encryption. Managing a remote Ethernet component (switch, router, and hub) is most effective using standard GUI-based protocols. These in turn are translated into a command line

Distributed with permission of author by ISA 2006

Presented at ISA EXPO 2006