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Cabling a Data Center to TIA-942 Standard

The Purpose of TIA-942 Standard

  • The purpose of TIA-942 standard is to provide requirements and guidelines for the Design and Installation of a data center or computer room
  • TIA-942 standard will enable design to be involved early in construction process
  • TIA-942 allows for long term planning of data centers to support growth and future applications

TIA-942 includes guidelines for data center design, cabling system infrastructure, telecommunications spaces and topologies, cabling systems, cabling pathways, redundancy and informative annexes.

What is a Data Center?

Data center is a building or portion of a building whose primary function is to house a computer room and it’s support areas.


Types of Data Centers

  • Private domain or enterprise data centers
  • Public domain data centers


Data Center Design

Coordination of all aspects of a data center is critical including

  • Telecommunications cabling system
  • Equipment floor plan
  • Electrical plans
  • Architectural plan
  • HVAC
  • Security
  • Lighting system

Recommended design process is

  • Estimate needs at full capacity for all equipment
  • Anticipate future growth over life of data center
  • Provide all requirements to architects and engineers
  • Create an equipment floor plan
  • Design telecommunications cabling system

The following figure shows the relationship of spaces in a data center


Data Center Tiers

  • Relates to levels of availability of infrastructure
  • Tier Classifications were originally defined by The Uptime Institute
  • Addresses critical systems of data center
  • Critical systems may have different ratings
  • Ratings can be degraded as data center load increases over time


Data Center Tier I – Basic

  • Single path for power and cooling distribution
  • No redundant components
  • May not have a raised floor
  • Susceptible to disruption from planned and unplanned activity
  • 28.8 hours of annual downtime


Data Center Tier II – Redundant Components

  • Single path for power and cooling distribution
  • Redundant components
  • Has a raised floor
  • Slightly less susceptible to disruptions than Tier I
  • 22.0 hours of annual downtime


Data Center Tier III – Concurrently Maintainable

  • Multiple power and cooling distribution paths – only one active path
  • Redundant components
  • Allows for any planned site infrastructure activity without disrupting computer hardware operation
  • 1.6 hours of annual downtime


Data Center Tier IV – Fault Tolerant

  • Multiple active power and cooling distribution paths
  • Redundant components
  • All computer hardware must have dual power inputs
  • Can sustain at least one worst-case, unplanned failure or event with no critical load impact
  • 0.4 hours of annual downtime

TIA-942 defines the following critical systems

  • Telecommunications
  • Architectural and Structural
  • Electrical
  • Mechanical


Tier 1 Data Center Telecommunications Requirements

  • Cabling, racks, cabinets & pathways meet TIA-942 requirements
  • Has 1 entrance pathway from access provider to facility
  • Single pathway for all cabling
  • Recommended labeling per ANSI/TIA/EIA-606-A and Annex B


Tier 2 Data Center Telecommunications Requirements

  • All requirements of Tier 1
  • Has 2 entrance pathways from access provider to facility
  • Routers & switches to have redundant power supplies and processors
  • Addresses vulnerability of service entering building


Tier 3 Data Center Telecommunications Requirements

  • All requirements of Tier 2
  • Be served by at least 2 access providers
  • A secondary entrance room
  • Redundant backbone pathways
  • Multiple routers and switches for redundancy
  • Addresses vulnerability of a single access provider


Tier 4 Data Center Telecommunications Requirements

  • All requirements of Tier 3
  • Redundant backbone cabling
  • Backbone cabling should be in conduit or have interlocking armor
  • Optional secondary distribution area
  • Optional redundant horizontal cabling
  • Addresses any vulnerability of the cabling infrastructure


Telecommunications Spaces

  • Entrance Room (ER)
  • Main Distribution Area (MDA)
  • Horizontal Distribution Area (HAD)
  • Zone Distribution Area (ZDA)
  • Equipment Distribution Area (EDA)



Entrance Room (ER)

  • Access provider demarcation point
  • Termination equipment for access provider cables
  • Interface between data center cabling and inter-building cabling
  • Pathways for all entrance cables
  • May be located inside or outside computer room


Main Distribution Area (MDA)

  • Central point of distribution
  • Includes the main cross-connect (MC)
  • May include horizontal cross-connect (HC)
  • Core routers & switches for LAN/SAN, PBX are located here
  • Located inside computer room
  • Must be at least one MDA



Horizontal Distribution Area (HAD)

  • Supports all the cabling to the equipment distribution areas
  • Includes the horizontal cross-connect (HC)
  • Switches for equipment in EDA located here
  • Located inside computer room
  • Minimum of one HAD per floor



Zone Distribution Area (ZDA)

  • Optional inter-connection point within horizontal cabling
  • Located between HAD and EDA
  • Allows frequent reconfiguration and flexibility
  • Should serve a maximum of 288 connections to avoid cable congestion
  • Shall be no active equipment (except for DC power)


Equipment Distribution Area (EDA)

  • Space for end equipment – servers, mainframes, tape drives
  • Horizontal cabling is terminated here onto patch panels
  • Point-to-point cabling between equipment is allowed



Recognized Cabling Media

  • 100-Ohm twisted-pair cable
  • 62.5/125um and 50/125um multimode fiber
  • Single mode fiber
  • 75 Ohm coaxial cable
  • Various options for each media such as traditional field terminations and pre-terminated configurations



Horizontal Cabling Topology


Horizontal Cabling

  • Cabling from HAD to EDA including horizontal cables, horizontal cross-connects, patch cords, optional consolidation point or zone outlet
  • 100 meter maximum horizontal cable distance. Note that distance reduced if zone area cable uses.





Backbone Cabling Topology



Backbone Cabling

  • Cabling between ER, MDA and HAD including backbone cables, main cross-connects, horizontal cross-connects, patch cords
  • Shall allow network reconfigurations and future growth



Cabling Pathways

  • Data centers shall adhere to ANSI/TIA-596-B specifications with exceptions noted in standard
  • Cabling shall not be routed through public spaces unless enclosed in secure pathways
  • Maintenance holes, pull boxes, splice boxes shall be locked and monitored


Cabling Pathways – Separation of Cabling

  • Proper distances must be maintained between electrical and twisted pair cables
  • Branch electrical circuits should be in watertight flexible metal conduit
  • Feeder electrical circuits to power distribution units should be in solid metal conduit
  • If using cable tray – Minimum of 12” between trays

Access Floors

  • Allocate separate aisles for power and telecommunications cabling
  • If not possible, then provide both horizontal and vertical separation

Cable Trays

  • Fiber and copper cabling in trays should be separated.
  • The benefits are to improve administration, minimize damage to smaller diameter cables.
  • If possible, fiber should be on top of copper


Cabling Pathways – Entrance Room

  • Should all be underground
  • Each access provider should have at least one 4” conduit
  • Shall meet ANSI/TIA-569-B


Cabling Pathways – Access Floors

  • Cabling under floor shall be in ventilated cable trays
  • Trays may be installed in multiple layers
  • Trays shall have a maximum depth of 6”
  • Access floor should use bolted stringer structure
  • Plenum rated cable is typical – consult AHJ



Cabling Pathways – Overhead Cable Trays

  • Trays may be installed in multiple layers
  • Trays shall have a maximum depth of 6”
  • In shared-tenant data center common spaces – solid bottom tray or minimum of 9 feet above finished floor.
  • Tray should be supported from ceiling




  • Reliability of telecommunications infrastructure needs to be increased. This is defined by Tier ratings
  • Very common to have multiple Service Providers
  • Entrance Pathways should be on opposite ends of building
  • If secondary ER required, access provider equipment should be able to operate independently, 20 meters of separation, and separate fire protection zones.


Redundancy – Main Distribution Area

If secondary distribution required:

  • Core routers and switches should be distributed
  • Circuits should be split
  • Separate fire protection zones
  • Separate power distribution units
  • Separate air conditioning systems


Infrastructure Redundancy



Redundancy – Backbone Cabling

  • Protects against outage caused by damage
  • Common to see additional cabling – MDA to HAD, HAD to HAD
  • Cabling should be run along different routes
  • If secondary distribution area – Not required HAD to HAD


Redundancy – Horizontal Cabling

  • Cabling should be run along different routes
  • Still must meet 100 meter maximum cable lengths
  • Critical equipment can be supported by 2 HAD’s – Separate fire protection zone


Informative Annex B


Identification of Cabling Infrastructure

Data centers should adhere to ANSI/TIA/EIA-606-A with exceptions as noted in standard


Identification Scheme for Floor Space

  • Floor space should track the data center grid
  • Use two letters and two numeric digits to identify each 600mm x 600mm (2ft X 2ft) floor tile
  • AA, AB, AC … AZ, BA, BB, BC .. and so on



Identification Scheme for Racks and Cabinets

  • All racks and cabinets should be labeled front and back
  • For rooms with access floors, each rack and cabinet to have a unique identifier based on floor tile coordinates
  • If cabinet rests on more than one tile, the same corner of each cabinet can be used to identify the grid location. Example: front right corner.


  • In data centers with multiple floors, the floor number should be added as a prefix to the cabinet number
  • Example: A cabinet whose right front corner is at tile AJ05 on floor 2, will be named 2AJ05


Identification Scheme for Patch Panels

  • Each panel to be labeled with an alpha character starting with A, B, C … Z etc. Starting from the top of the rack down
  • Horizontal wire management panels do not count when determining patch panel position





Patch Panel Identifier

  • Near end cabinet location and panel identifier to be followed by the far end cabinet location and panel identifier + port numbers
  • Example: AJ05-A to AQ03-B Ports 1-24



Cable and Patch Cord Identifier

  • Cables and patch cords should be labeled on both ends with the location of both ends of the cable
  • Example of the near end cable label – AJ05-A01 / AQ03-B01
  • Example of the far end cable label – AQ03-B01 / AJ05-A01




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