This document is by no means a complete
document on structured cabling. There are volumes of information
written on this topic. This document is intended to highlight certain
points, and assumes you have some knowledge of structured cabling.
||Main Distribution Facility. Main or Central wiring
closet, one per floor.
||Intermediate Distribution Facility. Secondary
wiring closet, when needed, on each floor or in peripheral buildings.
||Zone that falls within the area that can be served
by an internetworking device such as a hub. Usually a circle
180 meters in diameter - for Ethernet CAT5 cabling.
||The cabling from the workstation data outlet to
the termination point in the IDF or MDF (patch panel or 110
||Point of Presence. The demarcation or entry point
of the Phone Company's equipment and wiring in your building.
(The point where the phone company's wiring ends and your wiring
|Layer 1 Devices
||Network cabling, outlets, cable connectors, patch
panels, hubs, repeaters
|Layer 2 Devices
|Layer 3 Devices
||A collision domain is defined as a network segment
that shares bandwidth with all other devices on the same network
segment. When two hosts on the same network segment transmit
at the same time, the resulting digital signals will fragment
or collide, hence the term collision domain. It's important
to know that a collision domain is found only in an Ethernet
||A broadcast domain is defined as all devices on
a network segment that hear broadcasts sent on that segment.
When planning your network infrastructure think of it in the context
of the OSI 7 layer model.
The layers you will be dealing with are layers 1 through 3. The
Physical Layer, the Data Link Layer
and the Network Layer respectively.
Layer 1 deals with the network media (cabling) and the components
that connect the
network devices to the media, e.g. cable connectors, transceivers,
wall jacks, patch panels
and network cards (network cards can also be considered a layer
Should your cabling be Unshielded Twisted Pair (UTP), Shielded Twisted
Pair (STP) or COAX? If you are using UTP cabling should you use
Category 3, 4, or 5 cabling?
For today's networks you should be using Category 5e (CAT5e) or
higher data cabling. For your phone cabling you should use Category
Your LAN Technology and Physical Topology also have to be decided
on. Will you be using Ethernet, Token-Ring, FDDI? For your physical
topology will you use a star, extended star, bus, ring, etc.?
Hubs and Repeaters are also considered layer 1 devices so you will
need to decide if you will be using Hubs to connect your network
devices or perhaps a switch. Will you need repeaters to extend your
network? Careful planning should obviate the need for repeaters,
but there are times when you might need them.
Although not considered layer 1 devices, you should think about
racks and or cabinets to house your networking equipment.
Layer 2 devices are Switches and Bridges. Bridges are layer 2 devices
that are used to break up networks into segments. They are somewhat
of an outdated technology and should be avoided. A switch or router
can provide segmentation and are more intelligent devices.
In today's networking environment you should probably look at using
switches as the central point of your network as opposed to hubs.
Switches have become very affordable and have the benefit of breaking
up collision domains and well as providing dedicated bandwidth for
each device connected. Hubs are dumb, layer 1 devices that simply
pass on signals. There is no filtering and bandwidth is shared by
all devices connected to a hub. If you have a miniscule budget,
then you might have to settle for hubs
but try to avoid them.
Layer 3 is where routing takes place. If you are going to be subnetting
your network or connecting to other networks, either internal networks
or external networks (like the Internet), you will need to add a
Router(s) to your network. Routers are used to build scalable internetworks
and will impose a logical structure to you network. Routers, unlike
other networking devices (except VLAN capable switches), break up
broadcast domains which is of concern in multi-network environments.
Growth. Don't plan you network for just your current needs, plan
for the future. What will your networking needs be in 3 years?
Documentation. Document your cabling, hardware and software. Label
your cables! It is also a good idea to have a floor plan in each
of your wiring closets showing the location of data outlets and
their corresponding cable labels.
- In the TIA/EIA-568-A cabling standard, a minimum of one wiring
closet is required for each floor of your building. For every
1,000 square meters (10,000 square feet) or if any of your horizontal
cables will exceed 90 meters (295 feet), you should have an additional
- If your wiring closet is going to be a MDF, the floor should
be able to bear 100 lbs/ft2. If your wiring closet is going to
be a IDF, the floor should be able to bear 50 lbs/ft2.
- Wiring closets should have raised floors when possible to route
cabling. If raised floors aren't possible, you should use 30.5cm
(12.1 inches) overhead ladder racks to route your cables. All
cables should be tie wrapped.
- Floor coverings should be tile or some other finished covering.
No bare concrete or carpet should be used. At least two walls
should be covered with 20mm (3/4inch) fire retardant plywood that
is at least 2.4m (7.8 feet) high. If your wiring closet is also
going to be the POP, then you should have 4.6 meters (15 feet)
of plywood covered wall space for telephone wiring and equipment.
Walls (including the plywood) should be painted with a fire retardant
- Ceilings should not be dropped or false ceilings. This is primarily
a security concern.
- Air conditioning should always be present in any wiring closet.
A temperature of 21 degrees Celsius (69.8 degrees Fahrenheit)
should be maintained when all equipment is running. No water pipes
(unless required by fire codes for sprinklers) should be running
above the wiring closets.
- There should be at least 2 dedicated, non-switched AC duplex
outlets, each on it's own circuit, in each wiring closet. There
should also be one duplex outlet every 1.8m (5.9 feet) and they
should be 150mm (5.9 inches) above the floor.
- Fluorescent lighting should be avoided around cabling, but can
be used when properly installed. A wall switch for the room's
lighting should be just inside the door.
- The door to the wiring closet should be .9m (3 feet) wide and
swing open out of the room. There should be a lock on the door,
but anyone in the room should be able to open the door.
- If you are using distribution racks to mount your equipment
they should have a minimum of
15.2cm (6 inches) of wall clearance for the equipment plus another
30 to 45cm (1 to 1.5 feet) of space for access (figure at least
2.5 feet minimum).
- A floor plate 55.9cm (22 inches) should be used to mount the
rack to the floor for stability.
- If using a cabinet there should be 76.2cm (30 inches) of clearance
in the front for the door to swing open. Typical cabinets are
1.8m (6 feet) high x .74m (2.4 feet) wide x .66m (2.2 feet) deep.
- Data and Phone cables running into IDFs and MDFs should be in
10.2cm (4 inch) conduit. Likewise, all horizontal cabling from
workstations to wiring closets should be run through the same
size conduit. Preferably, cabling from workstations should be
run under a raised floor, but this is not always possible. An
additional 2 sleeve cores or conduits should be installed in each
wiring closet for future growth.
Conduit should be kept within 15.2cm (6 inches) of the walls,
and cabling coming into the wiring closets through conduit should
be run directly onto a 30.5cm (12.1 inch) wide ladder rack.
All holes or openings into wiring closets, that conduit runs through,
must be sealed off with a smoke and fire retardant material.
Horizontal cabling runs from the data outlet at the workstation
to the patch panel or horizontal cross-connect in the wiring closet
(IDF/MDF). It includes the outlet, horizontal cable, connectors,
and patch cords/cables that comprise the horizontal cross-connect.
- Grounding must conform to building codes as well as ANSI/TIA/EIA
- A minimum of 2 cables are required at each data outlet. Either
2 CAT5e cables or 2 Multi-mode fiber optic cables.
- Hybrid bundled cables (multiple, single UTP cables bundled together)
are allowed, but must meet TIA/EIA-568-A-3 standards.
- One transition point is allowed between different forms of the
same type of cable, but this should be avoided because transitions
add another potential failure point.
- 50 OHM COAX and 150 OHM STP cable should not be used for new
installations. This is outdated cable.
- Take into account the proximity of horizontal cabling to EMI
(electromagnetic interference) sources.
For example: motors, fluorescent lighting, power panels, surface
to air missle guidance systems, etc.
Maximum Distances for Horizontal Cabling
(Using CAT5 UTP cabling in an Ethernet network)
3 Meters – 90 Meters – 6 Meters
Work area patch cable.
From computer to wall
What is considered the Horizontal
Cabling. From wall outlet to the patch panel in the MDF or
IDF (Server Room).
The patch cable that cross
connects a patch panel
Backbone cabling, also called vertical cabling, is wiring used to
connect wiring closets to each other. Backbone cabling consists of
backbone cabling runs, intermediate and main cross-connects, cable
connectors, and patch cords used for backbone to backbone cross-connects.
Four types of network media are specified for backbone cabling
1. 100 ohm UTP 4 pair cable
2. 150 ohm STP 2 pair cable (outdated)
3. 62.5/125 -µm multimode fiber cable
4. Single-mode fiber cable
Connecting Horizontal and Backbone Cabling
There are a variety of ways of connecting workstations, IDFs and MDFs.
Below are some diagrams showing common methods of doing this. What
you see is an extended star physical topology which is very common
with Ethernet networks.
Some new terms are introduced, just to make things confusing. Main
Cross-Connect, and Intermediate Cross-Connect - MCC, HCC, ICC.
MCC - Main Cross-Connect. The same as the MDF. This is the main
See Figure A.
HCC - Horizontal Cross-Connect. The same as the IDF.
This is an intermediate
wiring closet that sits between the workstations and the MDF.
See Figure A.
ICC - Intermediate Cross-Connect. This is another wiring closet
that sits between
the IDF(s) and MDF. See Figure B.
Note: When using ICCs in your network layout, ANSI/TIA/EIA-568-A
states there can be only one ICC between the HCCs and the MCC. Also,
when using an ICC, no horizontal cabling (cabling from workstations)
connects directly to the ICC. All horizontal cabling connects to the
HCC or IDF.
Maximum Distances for Backbone Cabling
The maximum distances for cable runs vary from one type of cabling
to another. These distances can also be impacted by the way you design
your wiring closet layouts. As an example, if single mode fiber
optic cabling is to be used as a backbone media, and your network
layout includes a MDF (MCC) and an IDF (HCC) then the maximum distance
between the two wiring closets is 3000 meters.
If instead, you have a layout like Figure C below where you have an
ICC between the MDF and IDFs, then the maximum distance of the backbone
cable between the MCC and ICC is 2500 meters, and the maximum distance
of the backbone cabling from the ICC to the IDFs or HCCs is 500 meters.
See Figure C.