Frequently Asked Questions: Ethernet General Questions

 

  1. What is "CTRLink"?
  2. What is "Industrial Ethernet"?
  3. I am new to Ethernet. Do you have any information on it?
  4. Do you have any information on TCP/IP?
  5. How many 10 Mbps repeating hubs can I cascade and how long can the cables be?
  6. Do fiber ports auto-negotiate their data rates with connected equipment?
  7. After I reconfigure my RapidRing settings, why do they not take effect?

 

What is "CTRLink"?

CTRLink, pronounced "Control Link," is a trade name for a family of Industrial Ethernet products brought to you by Contemporary Control Systems, Inc. The CTRLink product family is comprised of Industrial Ethernet repeating hubs, switching hubs, and media converters. These products have been hardened for use in commercial and industrial automation systems where typical office grade equipment is impractical or cumbersome to install.

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What is "Industrial Ethernet"?

Our CTRLink Industrial Ethernet products are compliant to the industrial emission and immunity standards (EN50081-2 and EN50082-2). Office-grade equipment is not tested to these industrial standards. Our products use multi-layer circuit boards to improve their immunity and reduce emissions. Most office-grade Ethernet products use double-sided circuit boards. The CTRLink products are DIN-rail or panel mounted and are low voltage AC or DC powered.

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I am new to Ethernet. Do you have any information on it?

Yes. See our Newsletter Extension article"Introduction to Ethernet (Part 1)"

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Do you have any information on TCP/IP?

Yes. See our Newsletter Extension article "Introduction to the Internet Protocol"

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How many 10 Mbps repeating hubs can I cascade and how long can the cables be?

With shared Ethernet (half-duplex) you need to follow the rules in IEEE 802.3. The easiest method is the 5-4-3 rule which means a maximum of five segments, four repeaters (hubs) and only three mixing segments. Mixing segments are coaxial segments and since they are not popular let's ignore them. Therefore, if you have all twisted-pair segments and four hubs, the maximum end-to-end length (diameter) of your network is 500 meters. Let's say you want to have twisted-pair at the ends and fiber interconnecting the hubs, there are restrictions on the fiber length. Even though each fiber segment (10BASE-FL) can be up to 2 km, the total amount of fiber cannot exceed that amount. The standard specifically states that with a four segment, three-repeater network, the two inter-hub fiber segments cannot exceed 1 km each. Actually a better way of saying it is that the sum of the two segments cannot exceed 2 km. With this restriction, the maximum network diameter would be 2200 meters. The 5-4-3 rule is quite conservative. The 802.3 standard allows for a more exhaustive analysis to be made using what is called Transmission System Model 2, which could yield greater distances.

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Do fiber ports auto-negotiate their data rates with connected equipment?

Normally, only twisted pair ports can auto-negotiate data rates because fiber ports can only operate properly at the wavelength for which they are designed (850 nm or 1300 nm). Contemporary Controls fiber ports (with one exception discussed below) are fixed at the highest possible data rate. However, the new ANSI/TIA/EIA-785 standard — known as 100BASE-SX — includes an auto-negotiation scheme (similar to that of 100BASE-TX) for fiber ports. The standard defines a short-wavelength fiber modality for either 10 Mbps or 100 Mbps. Although Fast Ethernet can propagate via 850 nm fiber for only 300 m, this is still quite adequate for many industrial applications. The Contemporary Controls EIMC-10T/F miniature media converter provides auto-negotiation on both copper and fiber ports. A pair of these units, can establish a transparent fiber link between two auto-negotiating copper nodes, if the fiber length complies with the 100BASE-SX distance restriction.

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After I reconfigure my RapidRing settings, why do they not take effect?

To have your settings take effect, perform a software restart (remotely, if you prefer) of the master switch. Alternately, you can recycle power to any one of the RapidRing switches to make the new values effective.

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