Midterm-Network3

Question 1

Throughput:

Answer 1

Amount of data transmitted during given time period
Also called payload rate or effective data rate
Expressed as bits transmitted per second

Question 2

Bandwidth (strict definition):

Answer 2

Difference between highest and lowest frequencies medium can transmit
Range of frequencies

Question 3

Methods of transmission:

Answer 3

Full Duplex
Half Duplex
Simplex

Question 4

Full Duplex

Answer 4

signals are free to travel in both directions over a medium simultaneously

Question 5

Half-duplex

Answer 5

signals may travel in both directions over a medium but in only one direction at a time (Walkie-talkie)

Question 6

Simplex

Answer 6

signals may travel in only one direction

Sometimes called one-way or unidirectional

Question 7

The reason the wires are twisted:

Answer 7

to reduce crosstalk and electromagnetic interference (EMI)

Question 8

Benefits and drawbacks of Twisted Cable:

Answer 8

More wire pair twists per foot
More resistance to cross talk
Higher-quality
More expensive
Twist ratio
Twists per meter or foot
However, high twist ratio can result in greater attenuation

Question 9

Why on twisted-cable a high twist ratio can result in greater attenuation?

Answer 9

Because with more twists per feet, longer will be the cable, what leads to more attenuation of the signal.

Question 10

Most common twisted pair types:

Answer 10

Category (cat) 3, 5, 5e, 6, 6a, 7

CAT 5e or higher used in modern LANs.

Question 11

What are the 2 cable pinouts methods?

Answer 11

TIA/EIA 568A - normal

TIA/EIA 568B - change green by orange

Question 12

Computer communication: signals and pin number

Answer 12

1 - TX +
2 - TX -
3 - RX +
4 - NULL
5 - NULL
6 - RX -
7 - NULL
8 - NULL

Question 13

What is balanced mode of operation?

Answer 13

on tp, there are no grounded wires, so wires are set up as high and low frequency. Both are relative to a virtual ground.
In a balanced mode of operation, the balanced operation of the two wire pairs help to maintain the required level of performance in terms of crosstalk and noise rejection.

Question 14

Types of communications flaws:

Answer 14

Noise: EMI - Electromagnetic interference and cross talk
Attenuation: Loss signal strength due distance

Question 15

What are NEXT and FEXT:

Answer 15

NEXT - NEAR END cross talk occurs near source

FEXT - Far end cross talk occurs at the far end

Question 16

2 types to boost a sign:

Answer 16

Amplifier: Increase the voltage or strenght of the signal. It can boot the noise accumulated.
Repeater: Regenerates a digital signal on its original form. Retiming and regenerator

Question 17

RTT

Answer 17

ROUND TRIP TIME: Time for packet to go from sender to receiver, then back from receiver to sender.

Question 18

NVP:

Answer 18

Nominal Velocity of propagation: some percentage of the velocity of light in a vacuum and dependent on the type of cable being tested

Question 19

What are the benefits and drawbacks of fibre cables?

Answer 19

Benefits over copper cabling
Extremely high throughput
Very high noise resistance
Excellent security
Able to carry signals for longer distances
Industry standard for high-speed networking
Drawbacks
More expensive than twisted pair cable
Requires special equipment to splice

Question 20

SMF - Single Mode Fiber

Answer 20

Consists of narrow core (8-10 microns in diameter)
1 micron = 0.001 millimeter
Laser-generated light travels over one path; little reflection
Light does not disperse as signal travels
Can carry signals many miles before repeating is required
Rarely used for shorter connections
Due to cost
Used in long-haul and WAN, e.g., Internet backbone

Question 21

MMF (Multimode Fiber)

Answer 21

Contains a core with a larger diameter than single mode fiber. Common sizes: 50 or 62.5 microns
Laser or LED generated light pulses travel at different angles
Greater attenuation than single-mode fiber
Common uses
Cables connecting router to a switch
Cables connecting server on network backbone

Question 22

What is a campus network?

Answer 22

A campus network consists of interconnected LANs within a limited geographic area such as a college campus, a military base, or a group of commercial buildings

Question 23

What are the 6 subsystems of a structured cabling system?

Answer 23

Building Entrance
Equipment Room
Backbone cabling
Telecommunications closet
Horizontal cabling
Work area

Question 24

What are the basic components of a Horizontal Cabling?

Answer 24

Backbone cabling interconnecting between closets
Switch or hub
Patch panel
Patch cables
Cabling to the LAN (horizontal cabling)
Wall plate
Patch cable connecting the computer to the wall plate

Question 25

To adequately manage a network, record the following:

Answer 25

``` Network diagrams Physical topology Access methods Protocols Devices Operating systems Applications Configurations ```

Question 26

What is a Wireless LAN?

Answer 26

Wireless LAN or WLAN is a network composed of at least one WAP and at least one computer or handheld device that can connect to the WAP The advantages of wireless include: User mobility in the workplace A cost effective networking media for use in areas that are difficult or too costly to wire In order to ensure compatibility, the WAP and other wireless devices must all use the same IEEE 802.11 WLAN standard

Question 27

What are the 4 physical layers technologies in WLAN 802.11?

Answer 27

DSSS – Direct Sequence Spread Spectrum. Spread the transmitted signal over a wide bandwidth FHSS – Frequency Hopping Spread Spectrum. The transmit signal frequency changes based on a pseudorandom sequence Infrared OFDM – Orthogonal Frequency Division Multiplexing DSSS is most often used in 802.11b and 11g wireless networks, and OFDM is used in 802.11a.

Question 28

types of 802.11:

Answer 28

802. 11a (Wireless-A): This standard can provide data transfer rates up to 54 Mbps and an operating range up to 75 feet. It operates at 5GHz (Modulation – OFDM) 802. 11b (Wireless-B): This standard can provide data transfer rates up to 11Mbps with ranges of 100 to 150 feet. It operates at 2.4 GHz. (Modulation – DSSS) 802. 11g (Wireless-G): This standard can provide data transfer rates up to 54 Mbps up to 150 feet. It operates at 2.4 GHz. (Modulation – DSSS or OFDM) 802. 11n (Wireless-N): This is the next generation of high-speed wireless connectivity promising data transfer rates over 200+ Mbps. It operates at 2.4 GHz and also 5 GHz. (Modulation – DSSS or OFDM) 802. 11ac: This is the latest generation of high-speed wireless connectivity. This technology promises data rates up to 1Gbps. It operates over the 5GHz band 802. 11i: This standard for wireless LANs (WLANs) provides improved data encryption for networks that use the 802.11a, 802.11b, and the 802.11g standards 802. 11r: This standard is designed to speed handoffs between access points or cells in a wireless LAN. This standard is a critical addition to 802.11 WLANs if voice traffic is to become widely deployed

Question 29

802.11 DSSS

Answer 29

Implements 14 channels (each consuming 22MHz) over approximately 90MHz of RF spectrum in the 2.4GHz ISM (industrial, scientific, and medical) band Spread the transmitted data over a wide bandwidth (22MHz bandwidth channel)

Question 30

Network access in 802.11 uses a technique called Carrier Sense Multiple Access / Collision Avoidance (CSMA/CA)

Answer 30

Carrier Sense: In CSMA/CA, the client station listens for other users of the wireless network. If the channel is quiet, the client station may transmit. If the channel is busy, the station(s) must wait until transmission stops Collision Avoidance: Each client station uses a unique random back-off time and then checks all over again to find out if the channel if busy. This technique prevents the client stations from trying to gain access to the wireless channel as soon as it becomes quiet

Question 31

What are the Wireless Management Protocols?

Answer 31

authentication, association, data delivery, and privacy

Question 32

What is BBS (Basic Service Set)

Answer 32

The basic topology of the WLAN is the Basic Service Set (BSS). This is also called the independent Basic Service Set or “ad hoc” network. An example of an ad hoc network is provided. In this network, the wireless clients (stations) communicate directly with each other. This means that the clients have recognized the other stations in the wireless LAN and have established a wireless data link