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Presentation
Technical information
Ethernet network
Infrastructure
Presentation
The ConneXium Industrial Ethernet Offer is comprised of a complete family of
products and tools required to build the infrastructure of an Industrial Ethernet
network. In the following pages, information for the proper design of a network and
the selections of its components is offered.
Office Ethernet versus Industrial Ethernet
There are three main areas of differentiation between Ethernet applications in an
office environment and Ethernet applications in an Industrial environment, they are:
b
Environment
b
Layout (not physical layer specification)
b
Performance
Contrary to the office environment and even though ISO/IEC is working on it, there
are not yet clearly defined specifications for Ethernet devices targeted to Industrial
applications. The specifications of what it is called Industrial Ethernet are defined by
different agencies or entities based upon its nature and based upon what the
automation market has traditionally used.
The environmental specifications of Industrial Ethernet devices are today defined by
the traditional agencies that define the environmental specifications for standard
industrial devices (UL, CSA,
e
, ...).
The IEEE 802.3 defines the physical layer specifications of the Ethernet network
(
types of connectors, distance between devices, number of devices, ...) while
the 11801 (similarly to the TIAEIA 568B, and CENELEC EN 50173) provide
installers the layout guidelines.
The performance specifications are actually being worked on by ISO/IEC.
Ethernet 802.3 principles
The Ethernet 802.3 Link Layer is based on a collision detection mechanism
(
CSMACD): every node whose information has collided on the network realizes the
collision and re-sends the information.
The process of re-sending information causes delays in its propagation and could
affect the application.
A collision domain is a group of Ethernet end devices interconnected by hubs or
repeaters (devices that receive information and send it out to all their other ports, no
matter where the destination device is connected): it means that all devices will be
affected by collisions.
With the availability of full duplex switches (devices that receive information and send
it out just through the port to which the destination device is connected) the collision
domains have disappeared.
Therefore, for industrial automation applications it is strongly recommended to use
in every case full duplex switches to interconnect devices. In this way the collision
domains will be eliminated completely.
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