What is the name of the wiring closet that provides connections for a floor or section of a large building?

Cisco Semester 1 (Lessons 46-49 notes)
Instructor: Michael P. Harris

Lesson 46

Inhaltsverzeichnis Show

• What is a wiring closet called?
• What is in a wiring closet?
• What type of cabling is run between the floors of a building?
• What is the cable called that runs between telecommunications closets and between floors?

For an Ethernet LAN each run of horizontal cabling is attached to a central point in a star topology. The central point is referred to as the wiring closet. The wiring closet is where the patch panel and the hub are located.

The wiring closet must be large enough to accommodate the equipment and wiring located in it. Naturally, this will vary with the size of the LAN and the types of equipment required to operate it. Equipment required for some small LANs might take up as little space as a large filing cabinet, while a large local area network could require a full fledged computer room. Finally, the wiring closet must be large enough to accommodate future growth.

Recommended Sizing for Wiring Closets:

Service Area 1,000m/10,000' Wiring Closet Size: 10x11

Service Area 800m/ 8,000' Wiring Closet Size: 10x9

Service Area 500m/ 5,000' Wiring Closet Size: 10x7

EIA/TIA-569 specifies that there be a minimum of one wiring closet per floor and states that additional wiring closets should be provided for each area up to 1000 square meters when the floor area served exceeds 1000 square meters or the horizontal cabling distance exceeds 90 meters.

Any location selected for a wiring closet must meet certain environmental requirements. Broadly speaking these environmental requirements include sufficient power and HVAC. In addition, the location selected should be one that is secure from unauthorized access and meets all applicable building and safety codes.

All interior walls, or at least those on which equipment is to be mounted, should be covered with ¾" plywood that is raised away from the underlying wall a minimum of 1 ¾".

POP - Point of presence - The point of interconnection between the communication facilities provided by the telephone company and the building's main distribution facility.

If the wiring closet is to serve as the main distribution facility for the building, the telephone point of presence or POP, may actually be located inside the room. In such instances, interior walls at the POP and behind the PBX should be covered from the floor to the ceiling with ¾" plywood, and a minimum of fifteen feet of wall space should be provided for terminations and related equipment.

Fire retardant paint which meets all applicable fire codes should be used to paint all interior walls.

Rooms selected for wiring closets should not have a dropped or false ceiling. Failure to observe this specification could result in an insecure facility to which unauthorized access cannot be controlled.

To help control dust, floor coverings should be tile or other type of finished surface. Where required by certain types of equipment, anti-static protection should be taken.

If there is only one wiring closet in the building or if the wiring closet will serve as the main distribution facility, the floor must be able to bear a minimum load of 250 lb. per square foot, or as required by the equipment. Where the wiring closet is to serve as an intermediate distribution facility, the floor should be able to bear a minimum load of 100 lb. per square foot.

Where possible, rooms should have raised floors in order to accommodate incoming horizontal cabling runs from work areas. Where rooms cannot have or are not equipped with raised floors, there should be 12" ladder rack installed in a configuration designed to support all proposed equipment and cable.

No water or steam pipes should run through or above the room with the exception of a sprinkler system if required by local fire codes. Relative humidity should be maintained between 30% and 50%. Failure to adhere to these specifications could produce serious corrosion of the copper wires used in UTP and STP. Such corrosion would naturally impede optimal function of the network.

The wiring closet should include sufficient HVAC to maintain a room temperature of approximately 70 degrees Fahrenheit when all LAN equipment is fully functioning.

A wall switch to turn room lighting on and off should be located immediately inside the door. Due to the outside interference it generates, fluorescent lighting should be avoided.

If there is only one wiring closet in the building or if the room selected must serve as the main distribution facility, there should be at least one duplex power outlet every ten feet along each wall in the room. If the wiring closet is to serve as an intermediate distribution facility, at least two duplex power outlets should be located along each wall.

The door should be at least three feet wide and should swing open out of the room. This will ensure easy access to the room for workers and equipment. The wiring closet should lock from an outside access in such a way that exiting from the room is always possible.

Wiring hubs and patch panels may be wall-mounted using hinged wall brackets that are attached to the plywood covering the underlying wall surface. The purpose of the hinge on the wall brackets is to allow the assembly to swing out so workers and repairmen can easily access the back side. While this type of hinged mounting uses space economically, care must be taken to allow nineteen inches for the panel to swing out from the wall.

When distribution racks are used to mount patch panels and wiring hubs, care must be taken to allow at least a six inch depth for the equipment plus another twelve to eighteen inches for physical access to the back side. If a twenty-two inch floor plate is used to mount the distribution rack, this will provide stability and determine the minimum distance of the rack from the wall.

If a full equipment cabinet is the option chosen for mounting the patch panel, hub, and other equipment in the wiring closet, it will require at least thirty inches of clearance in front in order for the door to swing open. Typically, such equipment cabinets are seventy-two inches in height, twenty-nine inches wide, and twenty-six inches deep.

If the wiring closet is to serve as the main distribution facility, all cable leaving the room to intermediate distribution facilities and computer and communications rooms located on other floors of a building should be via four inch conduits or sleeved cores. Likewise, all such cable into IDFs should be via the same four inch conduits or sleeved cores.

Care should be taken to include additional conduits in any wiring closet design in order to provide for future anticipated growth. To meet this specification, a minimum of two excess sleeved cores or conduits should be provided in each wiring closet. Where construction permits, all conduits and sleeved cores should be kept to within six inches of walls.

Lesson 47

Think of the hub as the center point of a circle with lines of horizontal cabling radiating out from it like spokes from the center of a wheel. When you have completed this process, you should have a floor plan. Later when you pull cable for the network, you can use the floor plas as your cut sheet. Approach the project as if there is a need for multiple wiring closets, if not immediately, then at some point in the future as the network grows. Using a compass, draw circles with a radius of fifty meters from each of the potential hub locations.

EIA/TIA-568 specifies the maximum length of the cabling run, not the linear distance from the hub to the device. Distances of all horizontal cabling runs must include amount that is run through walls from ceilings to jacks as well as any service cable left at both ends.

Cut sheet - A rough diagram indicating where cable runs are located and the numbers of rooms they lead to.

A good place to start is to identify secure locations close to the POP that can serve as either the sole wiring closet or as the main distribution facility if intermediate distribution facilities are required. Remember, because the POP is where telecommunications facilities provided by the telephone company connect to the building's communication facilities, it is essential that the hub be located near it in order to facilitate wide area networking and connection to the Internet.

One wiring closet must be designated as the main distribution facility. Any additional wiring closets are referred to as intermediate distribution facilities.

Once you have drawn the circles, look at the floor plan again. Are there any potential hub locations whose catchment areas substantially overlap? If so, one of the hub locations can probably be eliminated. Are there any potential hub locations whose catchment areas can contain all of the devices that are to be connected to the network? If so, then one of them can probably serve as the wiring closet for the entire building. If more than one hub is needed to provide adequate coverage for all of the devices that will be connected to the network, is one closer to the POP than the other? If so, you will probably want to select it to serve as the main distribution facility.

Catchment area - Zone that falls within area that can be served by an internetworking device such as a hub.

Answer the following questions:

* Do any of the circles overlap?

* Can any of the potential wiring closet locations be eliminated?

* Do any of the circles provide coverage for all of the devices that will be connected to the network?

* Which of the potential wiring closet locations seems to be the best?

* Are there any circles where only a few of the devices fall outside the catchment area?

* Which potential wiring closet is closest to the POP?

Lesson 48

The building where the LAN is to be installed will provide work areas for 71 workers. In addition to workstations for these workers, seven printers will also be attached to the LAN.

The building where the LAN will be located occupies 7,200 square feet of office space contained on a single floor. The building is 60 feet wide by 120 feet long.

The ceiling height in all rooms unless specified otherwise is 12 feet. All ceilings are dropped ceilings unless specified otherwise.

All floors are poured concrete covered with industrial carpet unless specified otherwise.

On the floor plan provided with this lesson, the telephone company point of presence is labeled "POP." Men's restrooms are labeled "MR," and ladies' restrooms are labeled "LR." Potential locations for wiring closets have already been identified. They are marked on the floor plan as "A," "B," "C," "D," "E," "F," "G," "H," "I," and "J." Red dotted lines represent water pipes running through the ceiling space from the water heater to the restrooms. Blue dotted lines indicate where fluorescent lighting has been installed. Green dotted lines indicate where high voltage power lines have been routed through the walls. Magenta dotted lines indicate where heating a cooling ducts are located. All heating and cooling in the building is accomplished by use of a forced air system.

Location A is a small closet approximately three feet wide and eight feet deep. It has a dropped ceiling with fluorescent lighting. The switch that turns the light on and off is located just inside the closet door. The floor is carpeted and walls are of concrete block construction. There is only one electrical outlet in the closet. It is located on the back wall. Currently the room is used to store office supplies. Although a heating a cooling duct passes through the dropped ceiling space over the room, there is no vent into the room. The nearest thermostat for this section of the building is located in room 113. The door swings outward when it opens and is approximately three feet wide, however, because all staff members must be able to access the storage area, there is no lock on the door.

** Also centrally located, room D is slightly larger than room C. Its dimensions are approximately eight feet wide by ten feet deep. In addition, room D is near the POP. The room does not have a dropped ceiling. A heating and cooling duct that passes through the top of the room is also vented into the room. Temperatures inside the room are controlled by a thermostat located just inside the door. When the door is opened, it swings outward. The opening for the door is three feet wide. The floor is covered with ceramic tiles. Lighting is provided by an incandescent lighting fixture in the ceiling. The light switch that turns the light on and off is located just outside the door. There are eight electrical outlets in the room, two along each wall. Walls are of concrete block construction and are painted with a fire retardant paint. Currently, the room is used to store extra office equipment and is kept locked. The door can only be unlocked from outside the room.

Lesson 49

Horizontal cabling - term used by EIA-TIA 568 for the type of cabling that runs from the wiring closet to each work area.

When the 100 meter 'catchment area' of one 'wiring closet' is not enough to include all devices that need to be networked, repeaters can be used in an extended star topology. These repeaters/hubs, are located in wiring closets called IDFs and are linked by networking media to a central hub located in another wiring closet called the MDF.

So important is this central location that in a high rise building the MDF is usually located on one of the middle floors of the building even though the POP might be located on the first floor or in the basement.

Backbone - The part of a network that acts as the primary path for traffic that is most often sourced from, and destined for, other networks.

Vertical cabling/Backbone cabling - Cabling that provides interconnections between wiring closets, wiring closets and the POP, and between buildings that are part of the same LAN.

Backbone cabling consists of the backbone cabling runs, intermediate and main cross-connects, mechanical terminations and patch cords used for backbone-to-backbone cross-connection. Included in this are the vertical networking media between wiring closets on different floors, networking media between the MDF and the POP, and networking media used between buildings in a multi-building campus.

EIA/TIA-568 specifies four types of networking media that can be used for backbone cabling. These include 100 ohm unshielded twisted pair, 150 ohm shielded twisted pair, 62.5/125 micron optical fiber, and single-mode optical fiber.

Although EIA/TIA-568 recognizes 50 ohm coaxial cable, generally, it is not recommended for new installations, and it is anticipated that it will be removed the next time the standard is revised. Most installations today use the 62.5/125 µ fiber-optic cable as a matter of course for backbone cabling.

Hierarchical star topology - Extended star topology where a central hub is connected by vertical cabling to other hubs that are dependent on it.

HCC - Horizontal cross-connect. Wiring closet where the horizontal cabling connects to a patch panel which is connected by backbone cabling to the main distribution facility. (IDF)

MCC - Main cross-connect. Wiring closet that serves as the most central point in a star topology and where LAN backbone cabling connects to the Internet. (MDF)

ICC - Intermediate cross-connect. IDF that connects the horizontal cross-connect to the main cross-connect.

In the extended star topology, there are two ways in which an intermediate distribution facility can be connected to the main distribution facility:

1. Each (IDF) intermediate distribution facility can be connected directly to the (MDF) main distribution facility. Because the IDF is where the horizontal cabling connects to a patch panel in the wiring closet whose backbone cabling connects to the hub in the main distribution facility, this IDF is sometimes referred to as the horizontal cross-connect or HCC. Because it connects the backbone cabling of the LAN to the Internet, the main distribution facility is sometimes referred to as the main cross-connect or MCC.

2. A second way of connecting an IDF to the central hub uses a first IDF interconnected to a second IDF. The second IDF is then connected to the MDF. In such instances, the IDF that connects to the work areas is called the horizontal cross-connect, and the IDF which connects the horizontal cross-connect to the MDF is called the intermediate cross-connect or ICC. Note that no work areas or horizontal wiring connects to the intermediate cross-connect when this type of hierarchical star topology is used. When the second type of connection occurs, EIA/TIA-568 specifies that no more than one intermediate cross-connect can be passed through to reach the main cross-connect.

Single-mode fiber-optic cable (backbone cabling) - If used to connect the horizontal cross-connect to the main cross-connect, the maximum distance for the backbone cabling run is 3000 meters or 9840 feet. if the backbone cabling is used to connect the horizontal cross-connect to an intermediate cross-connect and the intermediate cross-connect to the main cross-connect, then the maximum distance of 3000 meters must be split between the two sections of backbone cabling. When this occurs, the maximum distance for the backbone cabling run between the HCC and the ICC is 500 meters or 1640 feet. The maximum distance for the backbone cabling run between the ICC and the MCC is 2500 meters or 8200 feet.

EIA/TIA-568 specifications for maximum distances for backbone cabling runs for each type of networking media:

Network Media Distance Distance Distance

Type HCC - MCC HCC - ICC ICC-MCC

-----------------------------------------------------------

62.5/125 fiber 2000m/6560' 500m/1640' 1500m/4820'

single mode 3000m/9840' 500m/1640' 2500m/8200'

UTP (voice) 800m/2624' 500m/1640' 300m/984'

UTP (data) data applications limited to 90m/295' total

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What is a wiring closet called?

What is in a wiring closet?

What type of cabling is run between the floors of a building?

What is the cable called that runs between telecommunications closets and between floors?