Among the changes from the standard’s original version, the revision recognizes Category 6 and recommends Category 6A for horizontal copper cabling.
By Patrick McLaughlin
The Telecommunications Industry Association (TIA) Engineering Committee TR-42 Telecommunications Cabling Systems has approved the publication of TIA-942-A, the revised Telecommunications Infrastructure Standard for Data Centers.
The revised standard was several years in development. In May 2010, Cabling Installation & Maintenance published an article authored by TIA-942-A co-editor Jonathan Jew, president of J&M Consultants. The article outlined the changes from the original TIA-942 standard that were anticipated to be included in TIA-942-A.
Recently, Jew summarized for us the changes in the new standard as follows.
Incorporate Addenda to TIA-942:
- Addendum 1 - Additional coaxial cabling specifications and revised distances
- Addendum 2 - General updates including revised tiering, the addition of Category 6A, 3-level lighting protocol, revised temperature and humidity limits
Restructuring standards - Integrate into the TIA-568-C series:
- Reference generic cabling topology (horizontal = cabling subsystem 1, distributor C = MC, B = IC, A = HC), terms, and MICE (mechanical ingress, climatic, electromagnetic) environmental classifications
- Move bonding and grounding content to TIA-568-B
- Move administration content to TIA-606-B
- Move racks and cabinets, power and telecom separation, environmental requirements (temperature and humidity) to TIA-569-C and new addendum
- Move outside plant pathways to TIA-758-B
Harmonize with international standards:
- Adopt the terms Equipment Outlet (EO) and External Network Interface (ENI - interface between external and internal networks in data center located in the entrance room)
- Standardize on LC for 1 or 2 fibers and MPO for more than 3 fibers on a single connector
- Remove distance limitation for horizontal cabling of optical fiber (based on application)
Higher Bandwidth Applications
- Remove support for Category 3 and Category 5e for horizontal cabling, retain for backbone cabling for console connections, telephone/modem lines, WAN circuits
- Minimum requirement of Category 6 for horizontal cabling, recommendation is Category 6A (or higher)
- Remove support for Om1 and Om2; minimum requirement is Om3; recommendation is Om4
- Retain singlemode fiber and 734/735 coax
- New section on energy efficiency
- Wider range of temperature and humidity (see TIA-568-C) based on new ASHRAE TC 9.9 guidelines
- Use of enclosures or enclosure systems to improve energy efficiency (cabinets with isolated supply or return, cabinet cooling systems, hot or cold aisle containment, panels and cable management that reduce air bypass, brushes/grommets on floor tiles)
- 3-Level Lighting Protocol - lighting levels based on occupancy and function (1. Lighting levels are minimal when the space is not occupied - enough for video surveillance. 2. Initial entry - safe passage. 3. Occupied - 500 lux.)
- Recommend the use of energy efficient lighting such as LED
Larger and modular data centers:
- New space, Intermediate Distribution Area (IDA), containing the Intermediate Crossconnect (IC)
- IDA also being adopted in ISO/IEC 24764 in new addendum, but will be called the Intermediate Distributor (ID)
- Elimination of requirement that centralized optical fiber technologies be limited to one building to accommodate modular data centers using outdoor containers/modules
Coaxial cabling specs
The first addendum made to the original TIA-942 standard, which was incorporated into the 942-A revision, deals specifically with the deployment of coaxial-style cabling systems in data centers.
The addendum (and now the 942-A standard) includes four primary elements. 1) It specifies additional requirements for connectors to be used for 75-ohm coaxial cabling in data centers (Type 734 and 735 coaxial cabling). 2) It specifies testing requirements for 75-ohm coaxial cabling in data centers. 3) It provides an allowance for longer horizontal cabling originating from the main distribution area (MDA) for coaxial cabling. 4) It amends E1, T1, E3 and T3 maximum circuit distances specified in Annex A of TIA-942.
Comments from TIA
Recently, Jonathan Jew and TIA’s associate vice president of technology and standards, Herb Congdon, discussed 942-A in a video produced by TIA. Their discussion included some of the standard’s implications for designers, installers and users of structured cabling systems.
In that video, Jew noted, “To harmonize with international standards, we eliminated the 100-meter channel restriction for horizontal cabling using optical-fiber cabling. It’s now based on application, and not limited to 100 meters.”
He also provided some detail on the addition of the intermediate distribution area (IDA) and intermediate crossconnect (IC) to the standard: “To provide flexibility in new data center designs being developed, we added the IDA and IC. This allows you to support large data centers and modular data centers much more easily.”
Also in that video, Congdon offered, “Clearly in the data center world, where there’s concentrated data supply chain going in and out, higher data rates are necessary. Many of the changes made to the standard were done so data centers could support these higher data rates. The 40- and 100-Gbit data rates are out there now, products are being displayed, and the data center standard is ready to accommodate those through these revisions.”
Jew was then asked to speculate on the direction that the standard’s next revision might take. (ANSI TIA standards are due for affirmation, revision or withdrawal on a five-year cycle.) Jew responded, “We’ll probably be adding support for the next generation of Ethernet, so that will be 400-Gig or maybe Terabit Ethernet. We’re also in TIA TR-42 working on the next generation balanced twisted-pair cabling, so it’s likely we will support that. And I think we’ll support something like 40-Gig over balanced twisted-pair cabling. We’ll also probably make some changes to support the evolving data center switch fabrics.”
In response to the same question, Congdon said, “I believe we’ll continue to see some evolution in energy efficiency and sustainable technologies that can be implemented in data centers and other locations. I think that by incorporating those into the data center standard, evaluating those technologies, we’ll continue to see some changes in our standards—not just the data center standard but others as well.”
The video also featured both Jew and Congdon discussing energy efficiency as it relates to data center operation. Jew discussed some of the specifications in 942-A that are also listed in this article, which are aimed at achieving energy efficiency.
Congdon spent some time discussing the Sustainable Technology Environments Program (STEP), of which TIA is a member.
The video can be viewed at www.tianow.org
Patrick McLaughlin is our chief editor.
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