Design and Documentation

Chapter 8

Network Design Issues Your first step in the process is to gather

information about the organization. This information should include: 1. organization's history and current status 2. projected growth 3. operating policies and management

procedures 4. office systems and procedures 5. viewpoints of the people who will be

using the LAN

Network Design Issues The second step is to make a detailed

analysis and assessment of the current and projected requirements of those people who will be using the network.

The third step is to identify the resources and constraints of the organization. Organization resources that can affect the implementation of a new LAN system fall into two main categories - computer hardware and software resources and human resources.

Network Design Issues

You must document an organization's existing computer hardware and software and identify and define its projected hardware and software needs. The answers to some of these questions will also help you determine how much training will be required and how many people will be needed to support the LAN.

Network Design IssuesThe questions you ask should include:

1. What financial resources does the organization have available?

2. How are these resources currently linked and shared?

3. How many people will be using the network?

4. What are the computer skill levels of the network users?

5. What are their attitudes toward computers and computer applications?

Following these steps and documenting the information in the framework of a formal report will help you estimate costs and develop a budget for the implementation of a LAN.

General Network Design ProcessIn technical fields such as engineering, the design process resources include . . .

1. designer—person doing the design

2. client—person who has requested and is probably paying for the design

3. users—persons who will use the product

4. brainstorming—generation of creative ideas

5. specifications development—usually numbers that will measure how well the design works

6. building and testing—process for meeting client objectives and satisfycertain standards

Network Design DocumentsThe following list includes some of the documentation that you should create as you design a network:

1. engineering journal

2. logical topology

3. physical topology

4. cut sheets

5. problem-solving matrices

6. labeled outlets

7. labeled cable runs

8. summary of outlets and cable runs

9. summary of devices, MAC addresses, and IP addresses

Planning Structured Cabling:Wiring Closet SpecificationsThe most important decision is the selection of the MDF. wiring closet size—TIA/EIA-568-A specifies that in an

Ethernet LAN the horizontal cabling runs must be attached to a central point in a star topology.

central point is the wiring closet where the patch panel and hub must be installed

size is important to accommodate growth considerations

walls, floors, and ceilings temperature and humidity locations and types of lighting power outlets room and equipment access cable access and support

Planning Structured Cabling:Wiring Closet Specifications

TIA/EIA-569 SPECIFIES THAT EACH FLOOR MUST HAVE A MINIMUM OF ONE WIRING CLOSET AND THAT ADDITIONAL WIRING CLOSETS SHOULD BE PROVIDED FOR EACH 1,000 M2 WHEN THE AREA OF THE FLOOR THAT IS SERVED EXCEEDS 1,000 M2 OR THE HORIZONTAL CABLING DISTANCE EXCEEDS 90m.

Walls, Floors, and Ceilings MDF—floor must be capable of bearing 4.8 kPA (100 lb./ft.2) IDF—floor must be capable of bearing 2.4 kPA (50 lb./ft.2) Floor should be raised where possible and covered in tile or

other finished surface. A minimum of two walls should be covered with 20-mm A-C

plywood that is at least 2.4 m high. In MDF where POP is located, interior walls should be

covered with 20-mm plywood with a minimum of 4.6 m of wall space provided for terminations andrelated equipment.

Walls and coverings should be fire retardant. Room should not have dropped or false

ceiling.

Temperature and Humidity

21o C when all LAN equipment is in full operation relative humidity—30 to 50 percent

Lighting Fixtures and Power Outlets If there is only one wiring closet or the closet is MDF, a

minimum of two dedicated, nonswitched AC duplex electrical outlet receptacles on separate circuit is required.

At least one duplex power outlet should be positioned every 1.8 m along each wall of the room, 150 mm above floor.

Wall switch should be located inside the room. 500 1x brightness required; fixtures 2.6 m above floor

Room and Equipment Access Door should be .9 m wide and should swing open out of the

room. Lock should allow anyone inside room to exit at any time. Wiring hub and patch panel may be mounted to a distribution

rack or to a hinged swing-mount rack secured to a wall. 48 cm should be allowed for the panel to swing out from wall.

If using distribution rack, it must have a minimum of 15.2 cm of wall clearance, plus another 30.5 to 45.5 cm for physical access by workmen. A 55.9 cm floor plate mounts rack to floor.

If patch panel, hub, or other equipment are mounted in a full equipment cabinet, they require at least 76.2 cm of clearance in front for door to swing open.

Cable Access and Support All cable should be protected by 10.2 cm conduit or

sleeve core. All horizontal cabling that runs from work areas to a

wiring closet should be run under a raised floor or through 10.2 cm sleeves that are placed above door level. (cabling ladder)

Planning Structured Cabling:Identifying Potential Wiring Closets

1. Start with floor plan of existing building.

2. Consider that the horizontal cabling system extends from the telecommunications outlet in the work area to the horizontal cross-connect in the telecommunications closet. It includes the telecommunications outlet, an optional consolidation pointer transition point connector horizontal cable, and the mechanical terminations and patch cords or jumpers that comprise the horizontal cross-connect.

Planning Structured Cabling:Identifying Potential Wiring Closets

Some points specified for horizontal cabling subsystem include:1. multipair and multiunit cables are allowed2. grounding must conform to applicable building codes and industry

standards3. minimum of two telecommunication outlets is required per work area

a. first outlet—100 UTP (Cat 5e recommended)b. second outlet—100 UTP (Cat 5e recommended)c. two-fiber multimode optical fiberd. one transition point is allowed between different forms of same

cable type (where undercarpet cable connects to round cable)e. additional outlets may be providedf. bridged taps or splices are not allowedg. application specific components shall not be installed as part of

horizontal cabling; must be placed external to telecommunications outlet or horizontal cross-connect

h. electromagnetic interference (EMI) must be considered

Planning Structured Cabling:Identifying Potential Wiring Closets

1. Start by looking for a wiring closet close to POP, where telecommunications services are provided by telephone company.

2. Determine how many wiring closets you will need.

3. Draw circles that represent a radius of 50 m from each of the potential hub locations; if there is any overlap, you could potentially eliminate one of the hub locations.

Planning Structured Cabling:Backbone Cabling

If the 100 m catchment area of a simple star topology wiring closet cannot provide enough coverage, the star topology can be extended by using hubs.

TIA/EIA-568-A specifies the use of one of the following: 100-ohm UTP (four pair) 150-ohm STP (two pair) Two-fiber duplex 62.5/125 micron optical fiber Multimode optical fiber

TIA/EIA recommends the use of Cat 5 or Cat 5e UTP for horizontal cabling when an Ethernet LAN uses a simple star topology.

Planning Structured Cabling:Backbone Cabling

The main hub or switch for an extended star topology is usually centrally located. This central location is so important that in a high-rise building, the MDF is usually located on one of the middle floors, even though the POP might be located on the first floor or in the basement.

Backbone cabling connects the POP to the MDF. Backbone cabling connects the MDFs to the IDFs on

each floor. Horizontal cabling runs radiate out from IDFs on each

floor. Horizontal cabling radiates from MDF to workstations on

same floor.

Planning Structured Cabling:Cabling for MDF and IDF Connections

The type of cabling that TIA/EIA-568 specifies for connecting wiring closets to each other in an Ethernet LAN extended star topology is called backbone cabling.

Backbone cabling is sometimes referred to as vertical cabling. Backbone cabling consists of:

backbone cabling runs intermediate and main cross-connects mechanical terminations patch cords used for backbone-to-backbone cross-

connections vertical networking media between wiring closets on

different floors networking media between the MDF and POP networking media used between buildings

Planning Structured Cabling:Backbone Cabling Media

TIA/EIA-568-A specifies four types of networking media that can be used for backbone cabling: 100-ohm UTP (four pair) 150-ohm STP (two pair) 62.5/125 micron multimode optical fiber single-mode optical fiber

The topology used when more than one wiring closet is required is the extended star topology.

Planning Structured Cabling:TIA/EIA-568-A Requirements

In the extended star topology, there are two ways in which an IDF can be connected to the MDF. In the first, each IDF can be connected directly to the

MDF. In this case, because the IDF is where the horizontal

cabling connects to a patch panel in the wiring closet, whose backbone cabling then connects to the hub or switch in the MDF, the IDF is sometimes referred to as the horizontal cross-connect (HCC).

The MDF is sometimes referred to as the main cross-connect (MCC) because it connects the backbone cabling of the LAN to the Internet.

Planning Structured Cabling:TIA/EIA-568-A Requirements

In the extended star topology, there are two ways in which an IDF can be connected to the MDF. The second method of connecting an IDF to the

central hub or switch uses the “first” IDF interconnected to the “second” IDF. The “second” IDF is then connected to the MDF.

The IDF that connects to the work areas is called the horizontal cross-connect.

The IDF that connects the HCC to the MDF is called the intermediate cross-connect (ICC).

No work areas or horizontal cabling connects to the intermediate cross-connect when this type of hierarchical star topology is used.

Planning Structured Cabling:Electricity and Grounding

Electricity is brought into our homes, schools, and offices by power lines that carry it in the form of alternating current (AC). Another type of current, called direct current (DC), is the kind found in a flashlight, car battery, and in the motherboard of a computer.

Electrical Issues that must be addressed:• AC Line Noise• ESD• Grounding Electrical Current

Planning Structured Cabling:Cabling and Grounding

Cabling and Electrical Issues that must be addressed:• Faulty Ground Wiring Problems• Avoiding Potential Dangerous Circuits

Between Buildings• Fiber-optic Cable Can Prevent Electrical

Shocks

Network Power Supply Issues: Power Line Problems

• Surge• A surge is a voltage increase above 110% of the normal

voltage carried by a power line. • Sag/Brownout

• A sag is a brownout that lasts less than a second. These incidents occur when voltage on the power line falls below 80% of the normal voltage.

• Spike• A spike is an impulse that produces a voltage overload on the

power line.• Oscillations and Noise

• Oscillation is an excessively long electrical wiring run, which creates an antenna effect .

Network Power Supply Issues: Power Line Problems

• Sources of Surges and Spikes•Lightening, cycles on electrical motors

• Surge and Spike Damage•Lockups, loss of memory, problems with data

• Surge and Spike Solutions•Surge protectors

• Sag and Brownout Solutions•UPS, backups

• Oscillation Solution•Rewiring

Summary• Layer 1 components include plugs, cables, jacks, patch

panels• To finish Layer 1 design, both a logical and a physical

topology must be generated.• Layer 2 devices such as switches reduce congestion

and collision domain size.• Layer 3 devices such as routers are used to build

scalable internetworks (larger LANs, WANs, networks of networks) or to impose a logical structure on the network.

• Databases and other shared resources as well as LANs link to WANs and to the Internet.

Summary

• Whenever you install a cable, it is important to document what you have done.

• A wiring closet is a specially designed room for wiring a data or voice network.

• Backbone cabling consists of backbone cabling runs, intermediate and main cross-connects, mechanical terminations, and patch cords used for backbone-to-backbone cross-connections.

• Surge suppressors are an effective means of addressing the problems of surges and spikes.