CompTIA Net+ Chapter 2 - Supporting Cabling and Physical Installations

CompTIA Net+ Chapter 2

How does data transfer work?

By modulating the properties of the transmission medium (electric current, infrared light, or radio waves) to encode a signal.

Ethernet media specifications are named using a three part convention. What is it often referred to?

xBASE-y

This describes the following:

• The speed or bit rate in megabits per second or gigabits per second

• The signal mode (baseband or broadband)

• A designator for the media type

The Ethernet protocol governing contention and media access is called

Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

What does 100BASE-TX refer to?

• Fast Ethernet working over Cat 5 (or better)

• Twisted Pair cobber cable

• Maximum supported link length of 100 meters (328 feet)

To support compatibility with hosts still equipped with 10 Mbps Ethernet interfaces, Fast Ethernet introduced what?

Autonegotiation protocol to allow a host to choose the highest supported connection parameters

Gigabit Ethernet does not support

Hubs, can be only implemented using switches

10/40GbE is not deployed in many access networks, but what is its use?

• Company’s that require very high-bandwidth transfers such as TV and film production

• Also widely used as backbone cabling

Fiber is often used for what?

High-bandwidth requirements like video editing

Describe Unshielded Twisted Pair Cable

• Type of copper cable that has been used for telephone systems and data networks

• Cable is completed with an insulating outer jacket

• Pairs are twisted at different rates to reduce external interference and crosstalk

• Solid or stranded conductor wires

Shielded cable may be required in environments with high levels of interference. What are some examples of this interference?

• Run near motors

• Run near generators

• Or even fluorescent lighting

Screened cable

• Has on thin outer foil shield around all pairs

• Designated as screen twisted pair (ScTP), foiled/unshielded twisted pair (F/UTP), or sometimes just foiled twisted pair (FTP)

Fully Shielded Cabling

Has a braided outer screen

Cat 5e (Class D)

• Cable Type - UTP or F/UTP

• Ethernet Standard - 1000BASE-T

• Max. Distance - 100m (328ft)

• Frequency - 100 MHz

• Connector - RJ45

Cat 6 (Class E)

• Cable Type - UTP, F/UTP, or U/FTP

• Ethernet Standard - 1000BASE-T or 10BASE-T

• Max. Distance - 100m (1000BASE-T), 55m (10GBASE-T)

• Frequency - 250 MHz

• Connector - RJ45

Cat 6A (Class Ea)

• Cable Type - UTP, F/UTP, U/FTP, or S/FTP

• Ethernet Standard - 10GBASE-T

• Max. Distances - 100m

• Frequency - 500 MHz

• Connector - RJ45

Cat 7 (Class F)

• Cable Type - S/FTP or F/FTP

• Ethernet Standard - 10GBASE-T

• Max. Distance - 100m

• Frequency - 600 MHz

• Connector - GG45/TERA

Cat 8/8.1 (Class I)

• Cable Type - U/FTP or F/UTP

• Ethernet Standard - 40GBASE-T

• Max. Distance - 30m

• Frequency - 2,000 MHz

• Connector - RJ45

Cat 8.2 (Class II)

• Cable Type - F/FTP or S/FTP

• Ethernet Standard - 40GBASE-T

• Max. Distance - 30m

• Frequency - 2,000 MHz

• Connector - GG45/TERA

RJ45 Connectors

• Used with 4-pair copper cables

• Used for Ethernet twisted pair cabling

• Have a plastic retaining clip

RJ11 Connectors

• Used with 2-pair copper cable

• Can support six positions, but only the center two contacts are wired

• In a telephone system, this pair carries the dial tone and voice circuit

• Used for telephone systems and to connect analog data modems to a phone jack

Plenum Space

• A void in a building designed to carry heating, ventilation, and air conditioning systems

• Typically false ceiling, though it could be constructed as a raised floor

• Effective conduit for fire

Cabling that passes between two floors is referred to as a what?

• Riser

• Cabling must be fire stopped

You can use ________ in place of __________, but never use riser-rated cables in place of plenum-rated cables.

• plenum-rated cables

• riser-rated cables

Coaxial Cable

• Made of two conductors that share the same axis

• Core conductor is made of solid or stranded copper wire

• Enclosed by plastic insulation

• Wire mesh wrapped around the plastic constitutes the second conductor

BNC Connector

• Bayonet Neill-Concelman

• Twist-and-lock mechanism

F-Type Connector

• Secured by screwing them into place

Twinaxial Cable

• Similar to coax but contains two inner conductors

• Used for daatacenter interconnects working at 10 GbE

• Maximum distance is up to about 5 meters for passive cable types and 10 for active cable types

• Terminated using Direct Attach Copper (DAC) transceivers

ANSI/TIA/EIA 568 identifies the following locations of subsystem within a structured cabling system:

• Work Area

• Horizontal Cabling

• Telecommunications Room

• Backbone Cabling

• Entrance Facilities/Demarc

Work Area

The space where user equipment is located and connected to the network, usually via a patch cable plugged into a wall port.

Horizontal Cabling

• Connects user work areas to an IDF

• When using copper cabling, IDF must be within 90m cabling distance of each wall port

Telecommunications Room

• Room/closet that houses an intermediate distribution frame and networking equipment

• The termination point for the horizontal cabling along with a connection to backbone cabling

Backbone Cabling

Connects IDFs to a main distribution frame

Entrance Facilities/Demarc

• Marks the point at which external cabling is joined to internal cabling via the MDF

• Entrance facilities are required to join the local exchange carrier’s network and for inter-building communications

• The demarc point is where the access provider’s network terminates and the organization’s network begins.

T568A Wire Color

• Pin 1 - Green/White

• Pin 2 - Green

• Pin 3 - Orange/White

• Pin 4 - Blue

• Pin 5 - Blue/White

• Pin 6 - Orange

• Pin 7 - Brown/White

• Pin 8 - Brown

T568B Wire Color

• Pin 1 - Orange/White

• Pin 2 - Orange

• Pin 3 - Green/White

• Pin 4 - Blue

• Pin 5 - Blue/White

• Pin 6 - Green

• Pin 7 - Brown/White

• Pin 8 - Brown

Patch Panel

• Has punch down blocks on one side and preterminated RJ45 modular ports on the other side

• Allows incoming and outgoing connections to be reconfigured by changing the patch cable connections

• Structured cabling running form the work area or forming a backbone is terminated at the back of the patch panel on the IDCs, either using T568A/T568B

Punch Down Tool

Terminates fixed cable

Cable crimper

Creates a patch cord

A single optical fiber is constructed from three elements

• Core provides the transmission path, or waveguide, for the light signals.

• Cladding reflects signals back into the waveguide as efficiently as possible

• Buffer is a protective plastic coating

Fiber optic cables fall into two broad categories. What are those categories?

• Single Mode Fiber (SMF)

• Multimode Fiber (MMF)

Single Mode Fiber

• Small core (8 to 10 microns)

• Long wavelength

• Uses a laser to generate a near infrared (1,310 or 1,550nm) signal

• Can support data rates up to 100 Gbps

• OS1/OS2 are two grades of SMF cable, with OS1 being for indoor use, and OS2 being for outdoor use

Multimode Fiber (MMF)

• Larger core (62.5 or 50 microns)

• Shorter wavelength light (850 or 1,300nm)

• Uses less expensive optics and is less expensive than SMF

• Does support such high signaling speeds or long distances

• Most suitable for LANs

OM1/OM2

• 62.5 micron cable is OM1

• 50 micron cable is OM2

• OM1/OM2 are mainly rated for application up to 1Gbps and use LED transmitters

OM3/OM4

• Also 50 micron cable, but manufactured differently

• Designed for use with 850nm vertical cavity surface emitting laser VCSEL

Straight Tip (ST)

• Early bayonet-style connect that uses a push-and-twist locking mechanism

• Mostly for multimode networks, but not widely used for Ethernet installations anymore

Subscriber Connector (SC)

• Push/pull design, allowing for simple insertion and removal

• Can be used for single or multimode

• Commonly used for Gigabit Ethernet

Local Connector (LC)

• Also known as Lucent Connector

• Small form factor with a tabbed push/pull design

• Similar to SC, but the smaller size allows for higher port density

• LC is widely adopted for Gigabit Ethernet and 10/40 GbE

Fiber Optic Cable Installation

• Patch cables for fiber optic can come with same connector or a mix

• Duplex patch cords must maintain the correct polarity, so that the Tx port on the transmitter is linked to the Rx port on the receiver and vice versa

• TIA/EIA cabling standard sets out a system of A to B polarity

• Each elements in the link must perform a crossover, and there must be an odd number of elements

Two finishing types for tip of ferrule

• Ultra Physical Contact (UPC)

• Angled Physical Contact (APC)

Ultra Physical Contact (UPC)

The faces of the connector and fiber tip are polished so that they curve slightly and fit together better

Angled Physical Contact (APC)

The faces are angled for an even tighter connection. APC cannot be mixed with PC or UPC

Multi-fiber push-on (MPO)

• Allows for low-footprint backbone or trunk cabling

• Bundles 12 or more strands terminated to a single compact ferrule

• Mostly used to aggregate 10/25 Gbps lanes into 40/100/400 Gbps

• Each lane normally requires two fiber strands

Bidirectional Transceivers

• Support transmit and receive signals over the same strand of fiber

• Uses WDM to transmit the Tx and Rx signals over slightly shifted wavelengths

Coarse Wavelength Multiplexing (CWDM)

• Supports up to 16 wavelengths

• Typically used to deploy four or eight bidirectional strands

Dense Wavelength Division Multiplexing (DWDM)

• Provisions greater numbers of channels

• Means that there is much less spacing between each channel and that it requires more precise and expensive lasers

Rack

• Steel shelving system designed for standard-sized equipment

• Using a rack allows equipment to be stored more securely and compactly

What environmental factors need to be monitored when it comes to equipment?

• Temperature

• Humidity

• Electrical

• Flooding

Temperature

High temperature will make it difficult for device and rack cooling systems to dissipate heat effectively. This increases the risk of overheating of components within the device chassis and consequent faults.

Humidity

More water vapor in the air risks condensation forming within a device chassis, leading to corrosion and short circuit faults. Conversely, very low humidity increases risks of static charges building up and damaging components.

Electrical

Computer systems need stable power supply, free from outages, voltage dips, and voltage spikes/surges. Sensors built into power distribution systems and backup battery systems can report deviations from a normal power supply.

Flooding

This may be natural or man made. Electrical systems need to be shut down immediately in the presence of any significant amount of water.

How is wattage calculated?

Volts * Current

How to calculate the maximum load for a rack?

Add up the watts used by each appliance power supply and divide by the circuit voltage

Power Distribution Unit (PDU)

Has circuitry to clean the power signals, provide protection against spikes, surges, and under-voltage events.

Class A Fire Extinguishers

Designed to combat fires fueled by ordinary combustible materials such as wood, paper, cloth, and plastics

Class C Fire Extinguishers

Gas-based extinguishing and can be used where the risk of electric shock makes other types unsuitable

Wet-pipe sprinklers

• Work automatically

• Triggered by heat

• Discharge water

• Constantly hold water at high pressure

Alternatives to wet-pipe systems

• Dry-pipe

• Pre-action

• Halon

• Clean agent

Dry-pipe

These are used in areas where freezing is possible; water only enters this part of the system if sprinklers are triggered elsewhere

Pre-action

System only fills with water when an alarm is triggered; it will then spray when the heat rises. This gives protection against accidental discharges and burst pipes and gives some time to contain the fire manually before the sprinkler operates.

Halon

Gas-based systems have the advantage of not short circuiting electrical systems and leaving no residue

Clean agent

Alternative to Halon. Known to not be damaging to the environment, it is also nontoxic to humans

Bit Rate (Bandwidth)

Amount of information that can be transmitted, measures in bits per second (bps).

Throughput

Average data transfer rate achieved over a period of time excluding encoding schemes, errors, and other losses incurred at the Physical and Data Link layers

Latency (Delay)

Another term used for speed in order to measure the speed at which packets are delivered.

Attenuation

Loss of signal strength, expressed in decibels

Interference

Anything that gets transmitted within or close to the channel that isn’t the intended signal

Cable Category Issues

• Cat 5e supports Gigabit Ethernet and could still be an acceptable choice for providing network links for workstations, but most new installations and upgrades would now use Cat 6 or better.

• Cat 6 can support 10 Gbps, but over a 55m maximum distance.

• TIA/EIA recommends Cat 6A for healthcare facilities.

• Cat 7 cable is always of a screened/shielded type and is rated for 10 Gbps applications up to 100m.

• Cat 8 is intended for use in datacenters only for short patch cable runs.

Cable Tester

• Reports detailed information on the physical and electrical properties of the cable

• Can test and report on cable conditions, crosstalk, attenuation, noise, etc

Wire Map Tester

Used to detect improper termination issues

Wire map testers can identify the following problems:

• Continuity (open)

• Short

• Incorrect pin-out/incorrect termination/mismatched standards

• Reversed Pair

• Crossed pair (TX/RX transposed)

Continuity (Open)

A conductor does not form a circuit because of cable damage or because the connector is not properly wired.

Short

Two conductors are joined at some point, usually because the insulating wire is damaged, or a connector is poorly wired.

Incorrect pin-out/incorrect termination/mismatched standards

The conductors in a pair have been wired to different terminals.

Crossed Pair

Conductors from one pair have been connected to pins belonging to a different pair.

Split Pair

Where both ends of a single wire in one pair are wired to terminals belonging to a different pair.

Tone Generator/Probe

Used to trace a cable from one end to the other.

Decibel (dB) loss

May mean that the link experiences signal degradation problems with high error rates and retransmissions resulting in reduced speeds and possibly loss of connectivity

Crosstalk

• Indicates a problem with bad wiring, a bad connector, or improper termination

• Higher values represent less noise

What are the various types of crosstalk that can be measured?

• Near End (NEXT)

• Attenuation to Crosstalk Ratio, Near End (ACRN)

• Attenuation-to-Crosstalk Radio, Far End (ACRF)

• Power Sum

• Alien Crosstalk

Near End (NEXT)

This measures crosstalk on the receive pairs at the transmitter end and is usually caused by excessive untwisting of pairs or faulty bonding of shielded elements.

Attenuation to Crosstalk Ratio, Near End (ACRN)

This is the different between insertion loss and NEXT. ACR is equivalent to a signal-to-noise ration. A high value means that the signal is stronger than any noise present; a result closer to zero means the link is likely to be subject to high error rates.

Attenuation to Crosstalk Ratio, Far End (ACRF)

Far-end crosstalk (FEXT) is measured on the receive pairs at the recipient end. The difference between insertion loss and FEXT gives ACRF, which measures cable performance regardless of the actual link length.

Power Sum

Gigabit and 10 GbE Ethernet use all four pairs. Power sum crosstalk calculations confirm that a cable is suitable for this type of application. They are measured by energizing three of the four pairs in turn.

Alien Crosstalk

This is signal traffic from cables in close proximity that causes interference to a disturbed or victim cable. This is commonly caused by cinching a cable bundle with ties to tightly and by poorly terminated cabling.

Cable Troubleshooting Strategies

• Physical inspection

• Reseat the cable

• Verify drivers

Physical Inspection

• Check the cable for any visible damage such as cuts, kinks, or severe bends.

• Ensure that the connectors are not damaged and are securely plugged into the network device and the computer.

Reseat the Cable

• Unplug the cable from both ends and then plug it back in. This can resolve loose connection issues.

Verify Drivers

• If the problem persists, the issue could be the drivers or a physical problem with the network adapter.

• Open Device Manager on your computer, find your network adapter in the list, and check if it’s working properly.

• If it is not working properly, you may need to update the drivers or replace the network adapter.