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

Redundancy

• 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