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Networking and Virtualization > Midterm-Network3 > Flashcards

Midterm-Network3 Flashcards

1
Q

Throughput:

A

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

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2
Q

Bandwidth (strict definition):

A

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

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3
Q

Methods of transmission:

A

Full Duplex
Half Duplex
Simplex

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4
Q

Full Duplex

A

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

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5
Q

Half-duplex

A

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

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6
Q

Simplex

A

signals may travel in only one direction

Sometimes called one-way or unidirectional

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7
Q

The reason the wires are twisted:

A

to reduce crosstalk and electromagnetic interference (EMI)

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8
Q

Benefits and drawbacks of Twisted Cable:

A 
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
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9
Q

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

A

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

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10
Q

Most common twisted pair types:

A

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

CAT 5e or higher used in modern LANs.

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11
Q

What are the 2 cable pinouts methods?

A

TIA/EIA 568A - normal

TIA/EIA 568B - change green by orange

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12
Q

Computer communication: signals and pin number

A 
1 - TX +
2 - TX -
3 - RX +
4 - NULL
5 - NULL
6 - RX -
7 - NULL
8 - NULL
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13
Q

What is balanced mode of operation?

A

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.

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14
Q

Types of communications flaws:

A

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

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15
Q

What are NEXT and FEXT:

A

NEXT - NEAR END cross talk occurs near source

FEXT - Far end cross talk occurs at the far end

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16
Q

2 types to boost a sign:

A

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

17
Q

RTT

A

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

18
Q

NVP:

A

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

19
Q

What are the benefits and drawbacks of fibre cables?

A 
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
20
Q

SMF - Single Mode Fiber

A

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

21
Q

MMF (Multimode Fiber)

A

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

22
Q

What is a campus network?

A

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

23
Q

What are the 6 subsystems of a structured cabling system?

A 
Building Entrance
Equipment Room
Backbone cabling
Telecommunications closet
Horizontal cabling
Work area
24
Q

What are the basic components of a Horizontal Cabling?

A

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

25
Q

To adequately manage a network, record the following:

A 
Network diagrams
Physical topology
Access methods
Protocols 
Devices
Operating systems
Applications
Configurations
26
Q

What is a Wireless LAN?

A

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

27
Q

What are the 4 physical layers technologies in WLAN 802.11?

A

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.

28
Q

types of 802.11:

A
  1. 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)
  2. 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)
  3. 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)
  4. 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)
  5. 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
  6. 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
  7. 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
29
Q

802.11 DSSS

A

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)

30
Q

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

A

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

31
Q

What are the Wireless Management Protocols?

A

authentication, association, data delivery, and privacy

32
Q

What is BBS (Basic Service Set)

A

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

Networking and Virtualization (3 decks)

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