Installation guide

Network Infrastructure for EtherNet/IP™
Planning the Infrastructure
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These networks can connect more than 60 devices with communication cable without using any other
components. Bus extenders or bridges increase the network length or add layout flexibility, but they are
optional.
Industrial Ethernet uses “star” topology to connect infrastructure components to each other and to end
devices. While industrial Ethernet requires that the cost and use of infrastructure components be
considered in the total automation system design, the star topology provides almost unlimited flexibility
for connecting to devices wherever they are located.
3.1.1 Implications of Multiple and Higher Data Rates
Device-level networks offer choices of several data rates versus distance options. Once these parameters
are chosen for a particular network, all attached devices must be configured to operate at the same data
rate. Industrial Ethernet, however, allows a mix of data rates within the same network, for example, 10
Mbps, 100 Mbps, and 1000 Mbps (1 Gbps). Higher speeds are generally used for connections (uplinks)
between infrastructure components, such as switches and routers. For backward compatibility purposes,
many industrial Ethernet devices are offered with both 10-Mbps and 100-Mbps capabilities, or all three
speeds.
The ability to mix 10-Mbps, 100-Mbps, and 1-Gbps data rates in the same system allows engineers to
balance the 1-Gbps benefits of maximizing throughput with the 10-Mbps benefits of higher immunity to
electrical noise and lower sensitivity to custom cable and connector termination variances. The lower data
rates of device-level networks allow long copper wire cable lengths of 500 meters (about 550 yards).
With the higher data rates of industrial Ethernet, fiber-optic cable and/or infrastructure components are
necessary for long distances.
3.1.2 Frame Size
A single frame of data on a device-level network is usually small (e.g., a CAN-based network contains
only up to 8 bytes of data). A single frame of industrial Ethernet can contain up to 1500 bytes of data. The
combination of high speed and high data capacity makes industrial Ethernet increasingly attractive as
more intelligence is embedded into smaller and less expensive devices.
3.1.3 Implications of Multiple Protocols
Device-level networks are designed to communicate using one protocol. Even in cases where the same
underlying technology is used for multiple networks (e.g., CAN technology for both DeviceNet and
CANopen), placing one device of a different protocol on the network causes errors that prevent
communication. However, IEEE Std 802.3-based Ethernet technology and infrastructure components
handle multiple protocols.
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One advantage to open-standards-based Ethernet technology is that the user can choose a cabling
approach and cable layout design, and select protocols no matter which vendors supply the products.
Another advantage is the seamless connection between the plant floor, office, and Internet/Intranet
worlds. With this connection, however, comes a challenge: keeping the enterprise and Internet network
message traffic off the plant-floor control system. To prevent this traffic from slowing the industrial
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IEEE 802.3, IEEE Standard for Information Technology –Telecommunications and Information Exchange between Systems –
Local and Metropolitan Area Networks -- Specific Requirements – Part 3: Carrier Sense Multiple Access with Collision
Detection (CSMA/CD) Access Method and Physical Layer Specifications (Incorporates IEEE Std 1802.3D).
http://standards.ieee.org/getieee802/portfolio.html