R&M Data Center Handbook

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3.1.4. TIA-942
Without a doubt, the American standard is currently the most comprehensive body of standards for data centers.
Not only is cabling described, but also the entire data center environment including the geographical location, as
well as a discussion of seismic activities. Among other things, the data center is divided up into so-called “tiers”, or
different classes of availability (see section 2.2.1). The data center must satisfy specific requirements for each
class in order to guarantee availability.
What differences from ISO/IEC exist, apart from cabling performance
• The interface to the external network may not be in the computer room with TIA-942.
• The maximum length of horizontal cabling may not exceed 300 meters, even with glass fibers.
• No minimum requirements are provided for cabling.
• The limits for Category 6A (≠ 6 A) are less strict than those of ISO/IEC 24764 or EN 50173-5.
The smallest common denominator of the data center standards listed is cabling. TIA-942 references the EIA/TIA-
568 series in the area of performance. TIA-942 itself is divided into three sections; TIA-942, TIA-942-1 and TIA-
942-2. All data center details are covered in the main standard. The use of coaxial cables is covered in TIA-942-1,
and the latest version of the Cat6A (copper) performance class, laser-optimized fibers (OM3 and higher), changed
temperature and ambient humidity as well as other changes in content are introduced in TIA-942-2. Cabling is
defined as follows in TIA.
Cabling Infrastructure:
• Copper cable: Category 3 – 6A
• Copper transmission path: Category 3 – Category 6A (Category 6A is recommended, TIA doesn’t use classes)
• Multi-mode optical fiber cable: OM1, OM2, OM3 (OM3 recommended)
• Single-mode optical fiber cable: 9/125 µm
• Coaxial cables: 75 ohm
Connectors for Copper Cabling:
• ANSI/TIA/EIA-568-B.2
Plug Connectors for Optical Fibers:
• SC duplex (568 SC) per TIA 604-3
• MPO/MTP ® multi-fiber connector per TIA 604-5 (only 12-fiber)
• Other duplex connectors like LC may be used.
A new version of TIA-942 (TIA-942A) was in the planning stages at the time this document was published. Since
this change includes important areas, a preview of the new version is meaningful.
• Combining TIA-942, TIA-942-1 and TIA-942-2 into one document
• Harmonization with TIA-568.C0, TIA-568.C2, TIA-568.C3
• Grounding is removed and integrated with TIA-607-B
• Administration is integrated with TIA-606-B
• Distribution cabinets and separation of data and power cables is integrated with TIA-569-C
• The limit restriction for glass fiber paths in horizontal cabling is rescinded.
• Category 3 and Category 5 are no longer allowed for horizontal cabling.
• The glass fiber for backbone cabling is OM3 and OM4. OM1 and OM2 are no longer allowed.
• LC and MPO plugs are a mandatory requirement for the data center.
• Adaptation of ISO/IEC 24764 terminology
Combining Bodies of Standards
None of the bodies of standards is complete. A body will either omit an examination of the overall data center, or
its permitted performance class will not allow for scaling to higher data rates. It is therefore recommended that all
relevant standards be consulted when planning a data center. The best standard should be used, depending upon
specific requirements. One example of this would be to use the cabling performance capability from the standard
which provides the highest performance requirement for cabling components. In the case of other properties,
other standards should be used if they handle these properties in a better way.
Recommendation:
A specification of the standards used must therefore be listed in the customer requirement specification in order to
avoid ambiguous requirements!
Page 50 of 156 © 08/2011 Reichle & De-Massari AG R&M Data Center Handbook V2.0