Exam Domain 1.0 Networking Concepts

Question 1

A measurable amount of light is reflected when it hits the ends of the cable.
Much of a cable’s reflection loss occurs at each cable connection.
When the light hits the boundary between the core and the cladding, it is reflected back into the core.
There is minor loss to the signal when this occurs, but it contributes to overall signal loss.

Answer 1

Reflection

Question 2

If the light hits the boundary between the core and the cladding at too steep of an angle, the light is refracted into the cladding instead of reflected back into the core, causing signal loss.
Some fiber optic cables are doped with impurities near the edge of the fiber so that the signals are bent instead of reflected back to the center of the core.
The loss due to this refraction is minor when compared with the benefits of confining the light to the center of the core.

Answer 2

Refraction

Question 3

Impurities in the fiber core can cause light to scatter.
Some of the light continues down the fiber.
The light that is scattered backwards contributes to the signal loss.

Answer 3

Scattering

Question 4

Impurities in the fiber can also absorb the light, converting it to another form of energy, such as heat. This is a major cause of signal loss.

Answer 4

Absorption

Question 5

Name 4 types of physical cable attributes which can contribute to signal loss

Answer 5

• Cable length - While higher quality cables carry light signals further, the longer the cable, the more signal absorption and the greater the signal loss.
• Connectors - Every connector causes some level of signal loss, mostly due to reflection. While patch cables at each end of a run are to be expected, minimize any other connections.
• Splices - There are tools that you can use to splice a cut fiber optic cable. However, the signal loss from a splice is comparable to the signal loss from a connector.
• Bends - Micro bends in the cable due to things such as temperature change or manufacturing anomalies can cause signal loss.

While you have little control over micro bends, even macro bends that can’t be detected by the human eye can contribute to signal loss.
The straighter the fiber optic cable, the less the signal loss.

Question 6

Signal loss is calculated by summing the average loss of all the components used in the cable run to generate an estimate of the total attenuation that will be experienced end-to-end.
This estimate is called a _____________________.

Answer 6

budget loss.

When calculating a loss budget for a segment of fiber optic cable, use the following guidelines.

• Connectors: 0.3 dB loss each.
• Splices: 0.3 dB loss each.
• Multi-mode cabling:
• 3 dB loss per 1000 meters when using an 850 nm light source.
• 1 dB loss per 1000 meters when using a 1300 nm light source.
• Single-mode cabling:
• 0.5 dB loss per 1000 meters when using a 1310 nm light source.

-0.4 dB loss per 1000 meters when using a 1550 nm light source

Question 7

The total attenuation should be no more than 3 dB less than the total power at the transmission source. This is called the ____________

Answer 7

link loss margin.

For example, if the total power output at the transmission source of a cable run is 15 dB, then the total attenuation over the cable run should not exceed 12 dB.

This ensures that the cable will continue to function as its components (such as the LED light transmitters and connectors) degrade with age and use.

Question 8

Physical contact (PC) polishing

Answer 8

Typically usually used with single-mode fiber. The ends of the fiber are polished with a slight curvature so that when the cable end is inserted into the connector, only the cores of the fiber touch each other.

Question 9

Super physical contact (SPC) polishing
Ultra physical contact (UPC) polishin

Answer 9

Fiber cable contact polishing method that use a higher grade of polish and have more of a curvature than PC polishing. This further reduces ORL reflections.

Question 10

Angled physical contact (APC) polishing

Answer 10

This type polishing is used to reduce back reflection as much as possible.

An APC connector has an eight-degree angle cut into the ferrule.

The angle cut prevents reflected light from traveling back into the fiber.

Any reflected light is bounced into the cable cladding instead.

You can use angle-polished connectors only with other angle-polished connectors.

Using an angle-polished connector with a non-angle-polished connector causes excessive insertion loss.

Question 11

This network tool, reflects a signal from the transmit port on a device to the receive port on the same device. Use the loopback plug to verify that a device can both send and receive signals.

Answer 11

Loopback Plug

There are loopback plugs for both copper and fiber connections.

A failure in the loopback test indicates a faulty network card.

A successful loopback test means the problem is in the network cabling or another connectivity device.

You can purchase pre-made loopback plugs, or you can make an inexpensive one by cutting the end of a cable and manually connecting the transmit wires to the receive wires. To do this, connect the wire from pin 1 to the wire at pin 3, and the wire at pin 2 to the wire at pin 6.

Question 12

____________ is an intelligent loopback device installed at the demarcation point for a WAN service. Key points are:

Answer 12

A SmartJack

Technicians at the central office can send diagnostic commands to the smartjack to test connectivity and performance between the central office and the demarc. (demarcation point)

When you contact a WAN service provider for assistance, the provider might execute a test using the smartjack.

A successful test indicates that the problem is within the customer premises equipment (CPE).

Question 13

Verifies that the cable can carry a signal from one end to the other and that all wires are in the correct positions.

Answer 13

Cable tester

High-end cable testers can check for various miswire conditions such as wire mapping, reversals, split pairs, shorts, or open circuits.

You can use a cable tester to quickly identify a crossover and a straight-through cable.
Most testers have a single unit that tests both ends of the cable at once.

Many testers come with a second unit that can be plugged into one end of a long cable run to test the entire cable.

Question 14

A special device that sends electrical pulses on a wire to discover information about the cable

Answer 14

A time-domain reflectometer (TDR)

The TDR measures impedance discontinuities (the echo received on wire in response to a signal on the same wire). The results of this test can be used to identify several variables:
Estimated wire length.
Cable impedance.
The location of splices and connectors on the wire.
The location of shorts and open circuits.

Question 15

This specialized tool, performs the same function as a time-domain reflectometer (TDR), but is used for fiber optic cables

Answer 15

Optical time-domain reflectometer
(OTDR)

The OTDR performs the same function as a TDR, but is used for fiber optic cables. An OTDR sends light pulses into the fiber cable and measures the light that is scattered or reflected back to the device. The information is then used to identify specifics about the cable:
The location of a break.
Estimated cable length.
Signal attenuation (loss) over the length of the cable.

Question 16

A multi-function tool that verifies that a cable or an installation meets the requirements for a specific architecture implementation.

Answer 16

Cable certifier

A certifier is very important for Cat 6 cable used with bandwidths at or above 1000 Mbps. Slight errors in connectors or wires can cause the network to function at 100 Mbps instead of the desired 1000 Mbps (10 Gbps).

Certifiers can also validate the bandwidth capabilities of network interface cards and switches. Many can detect the duplex settings of network devices.

Most certifiers include features of a toner probe, TDR, and cable tester.
Certifiers are very expensive and are typically used by organizations that specialize in wiring installations.

Question 17

A network tool composed of two devices used together to trace the end of a wire from a known endpoint to the termination point in the wiring closet

Answer 17

Toner Probe

Connect the tone generator to one end of the wire. It will send a signal on the wire.

In the wiring closet, touch the probe to wires or place the probe close to wires.

A sound at the probe indicates that the generated tone has been detected and the wire that you are touching is the termination point for the wire you are tracing.

Question 18

A device used to test various electrical properties.

Answer 18

A multimeter can measure several parameters:
* AC and DC voltage
* Current (amps)
* Resistance (ohms)
* Capacitance
* Frequency

Question 19

Unique device that tracks voltage conditions on a power line.

Answer 19

Voltage Event Recorder

Basic recorders track only undervoltage or overvoltage conditions.

More advanced devices track conditions over time and create a graph, saving data from a program running on a computer.

Some UPS systems include a simple voltage event recorder.

Use a voltage event recorder to identify periods of low or high voltage that can adversely affect network components.

Question 20

A specialized device that monitors the environmental conditions of a specific area or device and are often used to track the conditions within server rooms, such as temperature, humidity, water, smoke, motion, and air flow.

Answer 20

Environmental Monitor

Typically, computers (especially servers) have an internal monitor that measures fan speed and CPU temperature.

Many monitors sound an alarm if a specified temperature or other environmental condition is reached.

Question 21

Tool which removes the protective sheath of a cable in order to expose the conductive wire.

Answer 21

Wire strippers

Wire strippers are rated to specific gauge (cable width) ranges.

Most wire strippers are combination tools. They can strip, cut, and crimp cables.

Almost all wire strippers have multiple holes or can be adjusted for specific cable sizes.

Question 22

A common tool in networking used to attach connectors to wires

Answer 22

Crimping tool

Some crimpers are designed for power connections. A special crimper is used to attach RJ45 connectors to twisted pair cables.

Question 24

A type of cutting tool used to cut cables or wires to a specific length or to remove damaged sections.

Answer 24

Snips

A diagonal cutter is an example of a snip tool.

Question 25

A tool that uses heat to join two optical fibers together. It fuses them together end-to-end. This is done in situations when the cable is broken or too short for the purpose it’s being used for.

Answer 25

Fusion Splicer

The fusion splicer ensures that the two cables are fused together in an accurate and precise way to eliminate (as much as possible) any light being scattered or reflected back by the splice.

The source of heat used by the fusion splicer is usually an electric arc, but could also be a laser, a gas flame, or a tungsten filament through which current is passed.

Question 26

A ___________ is a vinyl plastic wire termination device with a sharp metal insert that cuts through the plastic insulating jackets of two wires and crimps them together.

Answer 26

Tap Splicer

You use it to make quick splices or connections using two or more pieces of wire within the recommended range of the tap splice.

Question 27

This network component is responsible for converting digital data into digital signals to be sent on the medium.

Answer 27

A Transceiver.

is responsible for converting digital data into digital signals to be sent on the medium.

To receive signals, the transceiver converts digital signals from the network to digital data for the PC.

The following are the most common types of transceiver modules:

A gigabit interface converter (GBIC) is a large transceiver that fits in a port slot and is used for gigabit media, including copper and fiber optic.

A small form-factor pluggable (SFP) is similar to a GBIC, but is a smaller size. An SFP is sometimes called a mini-GBIC.

SFP+ is a newer version of the SFP. SFP+ supports data rates as high as 10 Gbit/s, 8 Gbit/s Fiber Channel, 10 gigabit Ethernet, and the Optical Transport Network (OTU2 standard).

A 10 gigabit small form-factor pluggable (XFP) transceiver is similar to an SFP in size, but is used for 10 gigabit networking.
Quad (4-channel) SFP is a compact hot-pluggable transceiver that is also used for data communication applications.

Question 28

Known for converting digital data to analog waves in networking.

Answer 28

A modem.

A modem converts binary data to analog waves on the sending end (modulation) and then converts the analog waves back to binary data on the receiving end (demodulation).

Some computers, such as laptops, come with built-in NICs. Other computers use NICs that plug in to the system’s expansion slots or are external to the computer and connect through an existing computer port.

Question 29

Connects network interface cards that are using different media types.

Answer 29

Media Converter

Media converters work at the Physical layer (Layer 1).

Media converters do not read or modify the MAC address in any way.

Media converters convert one media type to another within the same architecture (such as Ethernet).

A media converter cannot translate between two different architectures. This must be done using a bridge or a router.

Converting from one architecture to another requires modifying the frame contents to modify the Data Link layer address.

Question 30

A device that connects two (or more) media segments on the same subnet, and it filters traffic between both segments based on the MAC address in the frame. This Layer 2 network device builds a database based on MAC addresses to use for making forwarding decisions.

Answer 30

Bridge

The process begins by examining the source MAC address of an incoming frame.

If the source address is not in the forwarding database, an entry for the address is made in the database, associating the MAC address with the media segment.

The destination address is then examined.
If the destination address is not in the database, the frame is sent out on all segments except for the one on which it was received.

If the destination address is in the database, the frame is forwarded to the appropriate segment if the segment is different from the one on which it was received.

Broadcast frames are forwarded to all segments except the one on which they were received.

Question 31

** Important note regarding Network Bridges **

Answer 31

You should be aware of the following regarding bridges:

Bridges are used to separate one part of a subnet from another. This eliminates unnecessary traffic between segments and keeps the network from wasting bandwidth.

All segments connected to a bridge are on the same subnet and share a common subnet address.

Bridges can connect two segments that use different types of network architecture.

For example, a bridge can connect a segment using Ethernet to a segment using 802.11 wireless.
Bridges are Layer 2 devices; they read the MAC address contained in a frame to make forwarding decisions.

Frame forwarding happens independently of the upper-layer protocols (such as TCP/IP).

Question 32

A multi-port bridge that performs filtering based on MAC addresses and provides additional features not found in a bridge.

Answer 32

Switch

While most bridges can process only a single frame at a time, switches can process multiple frames simultaneously.

Switches offer guaranteed bandwidth to each switch port.
Switches can make additional forwarding decisions based on the MAC address.

For example, a switch can be configured to accept frames from specific MAC addresses.
Like bridges, switches operate at Layer 2.

Unmanaged switches are autonomous in their function, requiring no port management or configuration.

Managed switches allow administrators to change the port configurations, including the following:
Port speed
Duplexing
Filters based on network adapter MAC addresses
VLAN assignment

Question 33

A_________ is router with additional security features.

Answer 33

Firewall

Firewalls can be programmed with security rules to restrict the flow of traffic between networks.

Firewall rules control the type of traffic allowed into a network and the type of traffic allowed out of a network.

A firewall can be either hardware devices or software installed onto operating systems.

Question 34

A switch that is capable of reading Layer __ (network) addresses and routing packets between subnets

Answer 34

Layer 3 switch.

A Layer 3 switch often provides better performance than a router, but it does not support as many features as a router.

Question 35

The acronym “MDF” stands for _______________.

Answer 35

Main Distribution Frame
The MDF is a cable rack that manages and connects the cables entering a building.

Question 36

The acronym “IDF” stands for _______________.

Answer 36

Intermediate Distribution Frame.

The IDF is a cable rack that manages and connects wiring for communication between the MDF and workstation devices. The cables run through the MDF, are distributed to each IDF, and finally go to specific workstations.

Question 37

What is the network schema called when subnets of different sizes are used to reduce IP address waste.

Answer 37

Variable-Length Subnet Mask (VLSM)

The first step is to create a table showing the different subnets and possible host addresses.

Note: For VLSM to work, the network must be using advanced routing protocols such as OSPF, BGP, and others.

VLSM is typically used by ISP’s and larger public networks as it requires complex configuration.

Question 38

When given a network IP address, a network administrator might have to determine the network, or subnet, it belongs to. This is done by using a process called __________ ..

Answer 38

ANDing
ANDing is done by multiplying each bit of the binary versions of the IP address and its subnet mask with each other and calculating the results
. Each bit can have the following results:

0 and 0 = 0
1 and 0 = 0
0 and 1 = 0
1 and 1 = 1
The result of the ANDing process is the network ID that the IP address belongs to.

Question 39

As networks become more complex, these routing tables can get quite large and complicated. When routers talk to each other, they share their routing tables.

The process of combining several subnets, which reduces the number of entries in a routing table is known as _________.

Answer 39

Supernetting

Supernetting is the process of combining several subnets. This reduces the number of entries in a routing table.

Supernetting has many advantages including:

Reducing the size of routing tables.
Simplifying the network overview.
Decreasing CPU and RAM resources on the routers.
Improving network performance.

The main thing to keep in mind when Supernetting, is that the networks must be in sequence. If they are not in sequence, the networks cannot be combined.