Chap 8 Design and Documentation

Andres, Wen-Yuan Liao

Department of Computer Science and Engineering

De Lin Institute of Technology

andres@dlit.edu.tw

http://www.cse.dlit.edu.tw/~andres

Overview

• Network Design and Documentation

• Document brainstormed ideas, problem solving matrices

Wiring closet specifications

Wiring and electrical techniques used in network building

Basic Network Design and Documentation

General design process

Network design issues

General network design process

Network design documents

General design process

Layer 1 designA logical and a physical topology

Layer 2 LAN topology Reduce congestion and collision

domain size

Layer 3 topologyBreak up both collision and

broadcast domains.

Network design issues

Gather information about the organization

Make a detailed analysis and assessment of the current and projected requirements

Identify the resources and constraints of the organization

Network design documents Engineering journal Logical topology/Physical topology Cut sheets Problem-solving matrices Labeled outlets/Labeled cable runs Summary of outlets and cable runs Summary of devices, MAC addresses, and IP addresses

Wiring Closet Specifications

Overview of wiring closet selection

Size

Environmental specification

Walls, floors, and ceilings

Temperature and humidity

Lighting fixtures and power outlets

Room and equipment access

Cable access and support

Overview of wiring closet selection

MDF:Main Distribution Facility/Facilities IDF:Intermediate Distribution Facilities

Size

The horizontal cabling runs must be attached to a central point in a star topologyThe central point is the wiring closet Where the patch panel and the

hub must be installed

Size

TIA/EIA-569 A minimum of one wiring

closet Additional wiring closets

for each 1,000 m2

Environmental specification

Power supply and heating/ventilation/air conditioning (HVAC) issues

Be secure from unauthorized access

Meet all applicable building and safety codes

Walls, floors, and ceilings

Bear the load MDF: 4.8 kPA (100 lb/ft²)IDF: 2.4 kPA (50 lb/ft²)

Raised floorAccommodate incoming horizontal c

ables

Floor coverings should be tile

Temperature and humidity

Maintain a room temperature of approximately 21° C No water or steam pipes running through or above the room, with the exception of a sprinkler system Relative humidity should be maintained at a level between 30%-50%

Lighting fixtures & power outlets

A minimum of two dedicated, non-switched, AC duplex electrical outlet receptacles, each on separate circuits

Florescent lighting should be avoided for cable pathways because of the outside interference that it generates

Room and equipment access

The door of a wiring closet should be at least .9 m wide, and should swing open out of the room, thus ensuring an easy exit for workers The lock should be located on the outside

Room and equipment access

Allow 48 cm for the panel to swing out from the wall

A distribution rack, then it must have a minimum 15.2 cm of wall clearance for the equipment, plus another 30.5-45.5 cm for physical access by workmen and repairmen

Cable access and support

If a wiring closet serves as an MDF, all cable running from it should be protected by 10.2 cm conduit or sleeved core

All horizontal cabling that runs from work areas to a wiring closet should be run under a raised floor

Cable access and support

Any wall/ceiling openings that provide access for the conduit, or sleeved core, must be sealed with smoke and flame-retardant materials

Identifying Potential Wiring Closets

Topology as floor plan

Selecting potential locations

Determining number of wiring closets

Identification practice

Topology as floor plan

In order to determine the location of a wiring closetDrawing a floor plan of the building Adding to it all of the devices that

will be connected to the networkComputers, printers and file servers

Selecting potential locations

Identify secure locations that are close to the POP

The POP is where telecommunications services, provided by the telephone company, connect to the building's communication facilities

Determining number of wiring closets

Use your compass to draw circles: a radius of 50 m from potential hub locations

If overlap, eliminate one of the hub locations

To see if one of them is closer to the POP than the other(s)

Horizontal and Backbone Cabling

Catchment area problems

MDF location in a multi-story building

Example of where you would use multiple wiring closets

Cabling for MDF and IDF connections

Backbone cabling media

TIA/EIA-568-A requirements for backbone cabling

Maximum distances for backbone cabling

Catchment area problems If the 100 m catchment area cannot provide enough coverage, it can be extended by using repeaters100 Ohm UTP (four pair) 150 Ohm STP-A (two pair) 2 fiber (duplex) 62.5/125 µm optical f

iber Multimode optical fiber

MDF location in a multi-story building

The MDF is usually located on one of the middle floors of the building

The POP might be located on the first floor, or in the basement

Cabling for MDF and IDF connections

Backbone cabling: vertical cablingConnect wiring closets to each

other

Backbone cabling mediaTIA/EIA-568-A 100 Ω UTP (four-pair) 150 Ω STP-A (two-pair) 62.5/125 µm multimode optical fiber Single-mode optical fiber

The IDF is sometimes referred to as the horizontal cross-connect (HCC)

The MDF is sometimes referred to as the main cross-connect (MCC)

Only one

Electricity and Grounding

Differences between AC and DC AC line noise Electrostatic discharge Grounding electrical current in computer equipment Purpose of grounding computer equipment Safety ground connections Safety ground connection problems

Differences between AC & DC

DC flows at a constant value when circuits are turned on

AC rises and falls in current values

AC line noise

Coming from a nearby video monitor, or hard disk drive

It does this by adding unwanted voltages to the desired signals

Prevent a computer's logic gates from detecting the leading and trailing edges of the square signal waves

Electrostatic discharge

ESDs can destroy semiconductors and data, in a random fashion, as they shoot through a computer

A solution that can help solve problems that arise from ESD is good grounding

Grounding electrical current in computer equipment

The safety ground wire is connected to any exposed metal part of the equipment

The motherboards and computing circuits in computing equipment are electrically connected to the chassis

This also connects them to the safety grounding wire, which is used to dissipate static electricity.

GroundingPrevent such metal parts from becoming energized with a hazardous voltage Circuit breakers and Ground Fault Circuit Interrupters (GFCIs) Surge suppressors and Uninterrupted Power Supplies (UPS) Be required to protect computing and

networking equipment

Safety ground connection problems

The earth ground between buildings is almost never the same

Cabling and Grounding Causes of ground potential problems

Networking devices and dangerous circuits

Faulty ground wiring problems

Avoiding potentially dangerous circuits between buildings

How fiber optic cable can prevent electrical shocks

Reasons for using UTP for backbone cabling between buildings

Causes of ground potential problems

When devices with different ground potentials are linked in a circuit, they can produce hazardous shocks

Networking devices and dangerous circuits

The closed circuit produced by the use of UTP cable would then allow electrical current to flow from the negative source to the positive source

One hand rule You should not use more than one hand at a

time to touch any electrical deviceThe second hand should remain in your pocket

Avoiding potentially dangerous circuits between

buildings Use fiber-optic cable as the backboneBecause glass is an insulator rather than a conductor, electricity does not travel over fiber-optic cables

Reasons for using UTP for backbone cabling between

buildings

Whenever copper is used for backbone cabling, it can provide a pathway for lighting strikes to enter a building

Network Power Supply Issues: Power Line

Problems Power problem classifications Normal mode and common mode Typical power line problems Sources of surges and spikes Surge and spike damage Surge and spike solutions Sag and brownout solutions Oscillation solution

Power problem classifications

Normal mode problem Exists between the hot and neutral

wire Do not, ordinarily, pose a hazard to

you or to your computer Be intercepted by a computer's power

supply, an uninterruptible power supply or an AC power line filter

Power problem classifications

Common mode problem If a situation involves either the

hot, or neutral wire, and the safety ground wire

Go directly to a computer's chassis without an intervening filter.

Typical power line problems Power disturbanceUnwanted voltage that is sent to

electrical equipment Include voltage surges, sags,

spikes, and oscillations

Another situation that can cause power problems is a total power loss

Surge

A voltage increase above 110% of the normal voltage carried by a power line

A few seconds

Hardware damage

Most computer power supplies that run at 120 V are not built to handle 260 V for any length of time

Sag/Brownout

A brownout that lasts less than a second

Voltage on the power line falls below 80% of the normal voltageCaused by overloaded circuits

SpikeAn impulse that produces a voltage overload on the power line

Spikes last between .5 and 100 microseconds

In simple terms, when a spike occurs it means that your power line has momentarily been struck with a powerful hit of at least 240 V

Oscillations and Noise

Oscillations are also sometimes referred to as harmonics, or noise A common cause of oscillation is an excessively long electrical wiring run, which creates an antenna effect.

Sources of surges and spikes

Probably the most common one is a nearby lightning strike

Utility switching operations performed by the local power company can also trigger electrical surges and spikes

Sources of surges and spikes

Inside your school, office, or buildingElevators, photocopiers, and air

conditioners, cycle on and off, they create momentary dips and surges in power

Surge and spike solutions

Surge suppressors

When surges or spikes come in, surge suppressors divert them to ground

A good rule of thumb to follow is to protect all networking devices with surge suppressors

Surge and spike solutions

If you protect one networking device with a surge suppressor, then you should protect all devices, including the telephone line, in the same way

Sag and brownout solutions

Every network should have some type of uninterruptable power supply

Oscillation solution

The best way to address the problem of oscillation is to rewire

Surge Suppressors and UPS Functions

Surge suppressors: networking device locations Surge suppressors: for power panel locations UPS: for certain LAN devices UPS: for certain electrical problems UPS: components UPS: differences in UPS features UPS: description and operation

Surge suppressors: networking device locations

Surge suppressors are usually mounted on a wall power socket, to which a networking device is connected

A device called a metal oxide varistor (MOV) is most often used as this type of surge suppressor

Surge suppressors: networking device locations

This type of surge suppressor has a limited lifetime, dependent, in part, on heat and usage

Surge suppressors: for power panel locations

By placing a commercial grade surge suppressor near the power panel, the impact on the network, of voltage surges and spikes diverted to ground, can be reduced

UPS: for certain electrical problems

An UPS is designed to handle only short-duration power outages If a LAN requires uninterrupted power, even during power outages that could last several hours, then a generator would be needed to supplement the backup provided by a UPS

UPS: components

InverterConvert low-level DC voltage of the

batteries into the AC voltage, normally supplied by the power line, to networking devices

battery charger Designed to keep the batteries in peak

condition during periods when the power line system is functioning normally

UPS: components

BatteriesGenerally, the bigger the

batteries in a UPS, the longer a period of time it will be able to support networking devices during power outages

UPS: description and operation

A good UPS should be designed to communicate with the file serverShut down files when the UPS

battery power nears its endA good UPS reports instances

when the server starts to run on battery power

Summary

Document what you have done

A wiring closet

Backbone cabling

Surge suppressors