TIA- 942 Describes Data Center Standards

Following set cabling standards have always ensured a safe and efficient operation of any device or industry. Not only do standards assist us in building cost effective systems, they also bring in a certain level of uniformity for all industries. They ensure proper design, installation and performance of the network and also enabled the industries to advance faster and further.

Data centers, until recently, did not have any established standards. Network administrators had to choose technologies and decipher how to properly implement them into an often-undersized space. In April 2005, Telecommunications Industry Association (TIA) came out with TIA-942 Telecommunications Infrastructure Standards for Data Centers, this being the first standard to successfully address data center infrastructure.

TIA- 942 talks of the following specifications:

  • Site space and layout
  • Cabling infrastructure
  • Tiered reliability
  • Power
  • Cooling


While choosing space for a data center, one must keep possible future growth and changing environmental conditions in mind. The interior of the data center also should be designed with plenty of “white space” that can accommodate future racks on cooling devices. According to TIA-942, the data center should include the following functional areas:

  • One or More Entrance Rooms

The Entrance Room may be located either inside or outside the data processing room. The standard recommends locating the entrance room outside of the computer room for better security. If located within the computer room, the Entrance Room should be consolidated with the MDA.

  • Main Distribution Area

The MDA is a centrally located area that houses the main cross-connect as well as core routers and switches for LAN and SAN infrastructures along with a horizontal cross-connect for a nearby EDA. The standard requires at least one MDA and specifies installing separate racks for fiber, UTP, and coaxial cable in this location.

  • One or More Horizontal Distribution Areas

The HDA is a distribution point for horizontal cabling and houses cross-connects and active equipment for distributing cable to the equipment distribution area. The standard specifies installing separate racks for fiber, UTP, and coaxial cable in this location. It also recommends locating switches and patch panels to minimize patch cord lengths and facilitate cable management.

  • Equipment Distribution Areas

Horizontal cables are typically terminated with patch panels in the EDA. The standard specifies installing racks and cabinets in an alternating pattern to create “hot” and “cold” aisles to dissipate heat from electronics.

  • Zone Distribution Areas

The ZDA is an optional interconnection point in the horizontal cabling between the HDA and EDA. Only one ZDA is allowed within a horizontal cabling run with a maximum of 288 connections. The ZDA cannot contain any cross-connects or active equipment.

  • Backbone and Horizontal Cabling

Backbone cabling provides connections between MDA, HDAs, and Entrance Rooms while horizontal cabling provides connections between HDAs, ZDA, and EDA. Each functional area must be arranged to prevent exceeding maximum cable lengths for both backbone and horizontal cabling.


TIA- 942 standard recommends

  • The use of laser-optimized 50μm multimode fiber for backbone cabling.
  • Installing the highest capacity media available for horizontal cabling to reduce the need for re-cabling in the future.
  • Maximum backbone and horizontal cabling distances based on the cabling media and applications to be supported in the data center.
  • 300m of backbone fiber optic cabling and 100m of horizontal copper cabling.

It provides several requirements and recommendations for cabling management.

  • The data center must be designed with separate racks and pathways for each media type, and power and communications cables must be placed in separate pathways.
  • Adequate space must be provided within and between racks and cabinets and in pathways for better cable management, bend radius protection, and access.



To provide a means for determining specific data center needs, the TIA-942 standard includes an informative annex with data center availability tiers which describes detailed architectural, security, electrical, mechanical, and telecommunications recommendations.

Tier I – Basic: 99.671% Availability

• Single path for power and cooling distribution, no redundant components (N)

• May or may not have a raised floor, UPS, or generator

• Annual downtime of 28.8 hours

• Must be shut down completely for perform preventive maintenance

Tier 2 – Redundant Components: 99.741% Availability

• Single path for power and cooling disruption, includes redundant components (N+1)

• Includes raised floor, UPS, and generator

• Annual downtime of 22.0 hours

• Maintenance of power path and other parts of the infrastructure require a processing shutdown

Tier 3 – Concurrently Maintainable: 99.982% Availability

• Multiple power and cooling distribution paths but with only one path active, includes redundant components (N+1)

• Annual downtime of 1.6 hours

• Includes raised floor and sufficient capacity and distribution to carry load on one path while performing maintenance on the other.

Tier 4 – Fault Tolerant: 99.995% Availability

• Planned activity does not disrupt critical load and data center can sustain at least one worst-case unplanned event with no critical load impact

• Multiple active power and cooling distribution paths, includes redundant components (2 (N+1), i.e. 2 UPS each with N+1 redundancy)

• Annual downtime of 0.4 hours



Determining power requirements requires careful planning and is based on the desired reliability tier. It may include two or more power feeds from the utility, UPS, multiple circuits to systems and equipment, and on-site generators.

Estimating power needs involves determining the power required for all existing devices and for devices anticipated in the future. Power requirements must also be estimated for all support equipment such as UPS, generators, conditioning electronics, HVAC, lighting, etc.


The standard incorporates specifications for encouraging airflow and reducing the amount of heat generated by equipments. It recommends the use of raised-floor system for more flexible cooling. The standard encourages hot and cold aisle arrangement.

The standard also suggests:

  • Increase airflow by blocking unnecessary air escapes and/or increasing the height of the raised floor
  • Spread equipment out over unused portions of the raised floor
  • Use open racks instead of cabinets, or use cabinets with mesh fronts and backs
  • Use perforated tiles with larger openings


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