applying tia 942 in datacenter

SEPTEMBER 2009 www.cablingbusiness.com

DATA CENTER SPACES AND INFRASTRUCTURE

The main elements of a data center,

defined by TIA-942, are:

Entrance room (ER): The space

used for the interface between data

center structured cabling system and

inter-building cabling, both access

provider- and customer-owned. The

ER interfaces with the computer room

through the MDA.

Main distribution area (MDA):

Includes the main cross-connect,

which is the central point of distribu-

tion for the data center structured

cabling system and may include a hor-

izontal cross-connect when equipment

areas are directly served from the

MDA. Every data center shall include

at least one MDA.

ogy advancements in system equipment

must be considered.

TIA-942, Telecommunications

Infrastructure Standard for Data Centers,

was released in April 2005. The pur-

pose of this standard is to provide

information on the factors that should

be considered when planning and pre-

paring the installation of a data center

or computer room. TIA-942 combines

within a single document all the infor-

mation specific to data center applica-

tions. This standard defines the tele-

communications spaces, infrastructure

components and requirements for each

within the data center. Additionally, the

standard includes guidance as to rec-

ommended topologies, cabling dis-

tances, building infrastructure require-

ments, labeling and administration,

and redundancy.

When designing a data cen-

ter, several factors should

be taken into consideration,

including standards compliance. TIA-

942, Telecommunications Infrastructure

Standard for Data Centers, details several

of the factors that should be considered

when designing a data center. When

implementing a structured cabling solu-

tion, the standard recommends a star

topology architecture to achieve maxi-

mum network flexibility. TIA-942 outlines

additional factors crucial to data cen-

ter design, including recognized media,

cable types, recommended distances,

pathway and space considerations, and

redundancy. In addition to standards

compliance, the need for infrastructure

flexibility to accommodate future moves,

adds and changes due to growth, new

applications, data rates and technol-

DATA CENTER TECHNOLOGY

Applying Standards in Data Center Network Design

By David Kozischek


Horizontal distribution area

(HDA): Serves equipment areas.

Equipment distribution area

(EDA): Is allocated for end equipment

and shall not serve the purposes of an

ER, MDA or HAD.

Telecommunications room (TR):

Supports cabling to areas outside the

computer room and shall meet the specifi-

cations of ANSI/TIA569B.

The components of the cabling infra-

structure, as defined by TIA-942, are as

follows:

– Horizontal cabling

– Backbone cabling

– Cross-connect in the ER or MDA

– Main cross-connect in the MDA

– Horizontal cross-connect in the TR, HDA, MDA

– Zone outlet or consolidation point in the ZDA

Figure 1

Figure 2

– Outlet in the EDA

In a data center including HDAs, the

maximum distance allowed for horizontal

cabling is 90 m, independent of media

type. With patch cords, the maximum

R educed Data C enter T opology

O�ces , Ops . C enter, S upport

R ooms

Ac ces s P roviders

Main Dis tribution Area(R outers , B ackboneLAN/S AN S witches ,P B X, M13 Muxes )

Zone Dis t Area

E quip Dis t Area(R ack/C abinet)


C omputerR oom

Horizontal

C abling

R educed Data C enter T opology

O�ces , Ops . C enter, S upport

R ooms

Ac ces s P roviders

Main Dis tribution Area(R outers , B ackboneLAN/S AN S witches ,P B X, M13 Muxes )

Zone Dis t Area



C omputerR oom

Horizontal

C abling

Horizontal

C abling

channel distance allowed is 100 m, assum-

ing 5 m of patch cord at each end of the

channel for connection to end equipment.

When a ZDA is used, horizontal cabling

distances for copper may need to be

reduced (Figure 1).

DATA CENTER TECHNOLOGY Applying Standards in Data Center Network Design

Blog at www.cablingbusiness.com/wordpress SEPTEMBER 2009 PAGE 11

Applying Standards in Data Center Network Design DATA CENTER TECHNOLOGY

Depending on the type and size of

the data center, the HDA may be collapsed

back to the MDA. This is a typical design

for enterprise data centers. In this scenario,

the cabling from the MDA to the EDA, with

or without a ZDA, is considered horizontal

cabling. In a collapsed design, horizontal

cabling is limited to 300 m for optical fiber

and 90 m for copper (Figure 2).

LOGICAL TOPOLOGIES FOR DATA CENTERS

While standards help guide the data

center physical infrastructure, the logical

data center infrastructure does not have

a standards body helping with design.

Logical architectures, as shown in Figure

3, vary based on customer preference and

are also guided by the electronics manu-

facturers.

Though a standard does not exist, there

are some common architecture best prac-

tices that can be followed. Most logical

architectures can be broken into four layers:

Core

Aggregation

Access

Storage

Core

The core layer provides the high-

speed connectivity between the data cen-

ter and the campus network. This is typi-

cally the area where multiple ISPs provide

connections to the Internet.

Aggregation

The aggregation layer provides a point

where all server area devices can share com-

mon applications such as firewalls, cache

engines, load balancers and other value-

added services. The aggregation layer must

be able to support multiple 10G and 1G

connections to support a high-speed switch-

ing fabric.

Access

The access layer provides the

connectivity between the aggregation

layer shared services and the server farm.

Since additional segmentation may be

required in the access area, three different

segments are needed:

Front-end Segment – This area con-

tains web servers, DNS servers, FTP and

other business application servers

Application Segment – Provides the

connection between the front-end servers

and the back-end servers.

Back-end Segment – Provides con-

nectivity to the database servers. This seg-

ment also provides access to the storage

area network (SAN)

Storage

The storage layer contains the Fiber

Channel director and other storage devic-

es such as magnetic disc media or tape.

TIA-942 Physical Architecture Area

Logical Architecture Area

MDA=Main Distribution Area

Maps to Core and Aggregation

HDA=Horizontal Distribution Area Maps to Aggregation

ZDA=Zone Distribution Area

Maps to Access and StorageEDA=Equip Distribution

area

Figure 4

Figure 3

MAPPING LOGICAL ARCHITECTURES TO TIA-942

The key for many data center design-

ers is how to translate the many logical

topologies onto a TIA-942 structured cabling

infrastructure. This translation will affect some

of the key design elements of a structured

cabling solution such as fiber counts, hard-

ware considerations and physical cable runs.

The first step is to translate the TIA-942 areas

(MDA, HDA, ZDA, EDA) to the logical archi-

tecture areas (core, aggregation, access,

storage). Figure 4 shows a comparison

between the two.

The next step is to take an example


logical architecture and translate it to a

TIA-942 structured cabling solution. In this

example, we will use a small data center

and map the logical architecture shown in

Figure 5 to the physical architecture of the

data center (racks and cabinets) shown in

Figure 6. The next step is to choose the

TIA-942 architecture that will best map to

the logical architecture shown in Figure 5.

Since this data center is small, a reduced

TIA-942 architecture will be implemented.

In this architecture, an MDA, ZDA and EDA

will be implemented.

In implementing this structured

cabling design, the datacenter will be seg-

mented based on the logical topology

shown in Figure 5. The segmentation will

be as follows:

1. Collapse the core switching LAN, SAN and aggregation switching in the MDA

2. Segment the access layer into three zones: front-end, application and back-end

Figure 5

DATA CENTER TECHNOLOGY Applying Standards in Data Center Network Design

Figure 7

Blog at www.cablingbusiness.com/wordpress SEPTEMBER 2009 PAGE 13

Applying Standards in Data Center Network Design INSTALLATIONFigure 6

3. Segment the storage into a separate zone

Each zone will use a middle-of-the-

rack interconnect solution for the cabling.

Within each zone, the EDAs will utilize a

top-of-the-rack interconnect. The EDAs

will serve the electronics in each cabinet

and the ZDAs will serve the EDAs. The

ZDAs will homerun back to the MDA,

where they will terminate in a main cross-

connect (MC). This is shown in Figure 7.

CONCLUSIONWhen designing a data center, there

will be many different types of logical

architectures to choose from. These logi-

cal architectures will be deployed over

a hardware and cabling infrastructure.

The TIA-942 Structured Cabling Standard

provides guidance in how to properly

map any logical architecture into a physi-

cal architecture. When applied correctly,

the structured cabling system installed

today will serve the needs of the data

center now and in the future.

With more than 15 years of experience in

communications technology, David Kozischek

currently serves as market manager, Data

Centers for Corning Cable Systems. Kozischek

joined Corning Cable Systems in 1990 and has

held positions in Engineering Services as a senior

field engineer and senior systems engineer;

Strategic Planning and Business Development as

technology manager; and Global Strategic Growth

as a technology discovery manager.

applying tia 942 in datacenter

Documents