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IT Networking Tech > Chapter 3 > Flashcards

Chapter 3 Flashcards

1
Q

Network topology

A

describes how a network is physically laid out and how signals travel from one device to another (the physical layout of the devices does not describe how signals travel from one device to another) (for this reason network topologies are categorized into physical and logical topologies)

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2
Q

physical topology

A

the arrangement of cabling and how cables connect one device to another in a network

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3
Q

logical topology

A

the path data travels between computers on a network

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4
Q

Major physical topologiies

A

bus, star, ring, point-to-point

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5
Q

Physical bus topology

A

continuous length of cable connecting one computer to another in a daisy-chain fashion (the simplest physical topology)

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6
Q

Weaknesses of physical bus topology

A

1: Limit of 30 computers per cable segment
2: Maximum total length of cabling is 185 meters
3: Both ends of the bus must be terminated
4: Any break in the bus breaks down the entire network
5: Adding or removing a machine brings down the entire network temporarily
6: Technologies using this topology are limited to 10 mbps half-duplex communication since they use coaxial cabling

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7
Q

How data travels in a physical bus

A

Electrical pulses (signals) travel the cable’s length in all directions. Signal continues until it is weakened or absorbed by a terminator. If not terminated signal bounces at end of medium

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8
Q

signal propagation

A

Signal travel across the medium and from device to device

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9
Q

terminator

A

electrical component called a resistor that absorbs the signal instead of allowing it to bounce

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10
Q

Physical star topology

A

uses a central device (hub or switch) to connect computers

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11
Q

Advantages of a Physical star topology

A

1: Must faster technologies than a bus
2: Centralized monitoring and management of network traffic are possible (Hubs and switches can include software that collects stats about network traffic patterns and detect errors)
3: Easier network upgrades (as long as cabling and NIC support it, can easily be updated by replacing the central device)

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12
Q

Extended star topology

A

When number of devices exceeds the ports on a single device you can use a few central devices to connect to one central device (if each switch has 3 ports and you have 9 computers, one switch would be connected to 3 switches, and those 3 switches would be connected to 3 computers each)

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13
Q

How data travels in a physical star

A

Depends on type of central device, central device determines logical topology (hub = logical bus, switch = logical switching, MAU = logical ring)

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14
Q

Major disadvantage of a physical star

A

If the central device goes down, the entire network goes down

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15
Q

Physical ring topology

A

Similar to a physical bus topology except that instead of terminating at each end, the cabling is brought around from the last device to the first to form a ring

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16
Q

network backbone

A

cabling used to communicate between LANs or between hubs and switches

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17
Q

How data travels in a Physical ring topology

A

Data travels in one direction. If any station fails data can no longer be passed along

FDDI uses dual ring. Data travels in both directions so that one ring failure does not break network

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18
Q

FDDI info

A

Operates using fiber-optic cable at 100 Mbps

Extended star topologies with Gigabit Ethernet has largely replaced FDDI

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19
Q

Point-to-point topology

A

Direct link between two devices (mostly used in WANs)

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20
Q

Point-to-multipoint topology

A

a central device communicates with two or more other devices. All communication goes through the central device.

Often used in WANs where a main office has connections to several branch offices via a router. A single connection is made from the router to a switching device that directs traffic to the correct branch office.

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21
Q

Mesh topology

A

Connects each device to every other device in a network

Consists of multiple point-to-point connections for the purposes of redundancy and fault tolerance

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22
Q

Mesh topology advantages/disadvantages

A

Purpose of creating a mesh topology is to ensure that if one or more connections fail, there’s another path for reaching all devices on a network

Expensive due to multiple interfaces and cabling

Found in large WANs and internetworks

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23
Q

Logical topology

A

describes how data travels from computer to computer

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24
Q

Network technology

A

method NIC uses to access the medium and send data frames

Also called Network interface layer technologies, network architectures, data link layer technologies

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25
Q

LAN examples of Network technologies

A

Ethernet
802.11 wireless
Token Ring

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26
Q

WAN examples of network techonologies

A

Frame Relay
FDDI
ATM

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27
Q

Unshielded Twisted Pair (UTP)

A

most common media type in LANs

Consists of 4 pairs of copper wires each twisted together

Comes in numbered categories

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28
Q

Fiber-optic cabling

A

uses thin strands of glass to carry pulses of light long distances and at high data rates

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29
Q

Coaxial cable

A

obsolete as a LAN medium but is used as the network medium for internet access via a cable modem

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30
Q

Two main ways network technologies can use media to transmit signals:

A

Baseband or Broadband

31
Q

Baseband

A

sends digital signals in which each bit of data is represented by a pulse of electricity or light. Sent at a single fixed frequency and no other frames can be sent along with it

32
Q

Broadband

A

uses analog techniques to encode binary 1s and 0s across a continuous range of values. Signals flow at a particular frequency and each frequency represents a channel of data

33
Q

Ethernet

A

the most popular LAN technology
supports a broad range of speeds (10 Mbps to 10 Gbps)

Can operate in physical bus or physical star topologies and logical bus or switched logical topologies

34
Q

Ethernet addressing

A

Every station has a MAC address

Each MAC address has 48 bits expressed as 12 hexadecimal digits

Incoming frames must match NIC’s address or broadcast address (FF-FF-FF-FF-FF-FF)

Once processed by the NIC, incoming frames are sent to the network protocol for further processing

35
Q

Media access method

A

Rules governing how and when the medium can be accessed for transmission

36
Q

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

A

ethernet uses this

37
Q

Carrier Sense

A

Listen before sending (must hear silence)

38
Q

Multiple Access

A

If two or more stations hear silence, multiple stations may transmit at the same time

39
Q

Collision Detection

A

If two or more stations transmit, a collision occurs and is detected by the NIC, all stations must retransmit

40
Q

Collision domain

A

the extent to which signals in an Ethernet bus topology network are propagated.

All devices in a collision domain are subject to the possibility that whenever a device sends a frame, a collision may occur

41
Q

Cyclic Redundancy Check (CRC)

A

error-checking in a frame’s trailer.

CRC is used to determine that data is unchanged

If a frame is detected as damaged it is discarded with no notification

42
Q

Half-duplex

A

works like a two way radio, can talk and listen but not both at the same time.

Ethernet on hubs only works in half-duplex

43
Q

Full-duplex

A

means NIC/switch can transmit and receive simultaneously (like a telephone)

CSMA/CD is turned off

Most switches operate in full-duplex

44
Q

Ethernet Standards representation

A

XBaseY

X - designates the speed of transmission

Y - specifies the type of media (T - twisted pair, FX - fiber optic)

45
Q

10BaseT

A

Uses two of the four wire pairs

Runs over Category 3 or higher UTP cabling

Highly susceptible to collisions and is obsolete

46
Q

100BaseTX

A

Most common Ethernet variety

Runs over Category 5 or higher UTP

Uses two of four wire pairs

Switches can be used to interconnect multiple hubs

47
Q

Two types of 100BaseTX hubs:

A

Class 1 - can have only one hub between communicating devices

Class 2 - can have a maximum of two hubs between devices

48
Q

100BaseFX

A

Runs over two strands of fiber optic cabling

Typically used as backbone cabling between hubs or switches. Also used to connect clients or servers when immunity to noise and eavesdropping is required

49
Q

1000BaseT

A

Also known as Gigabit Ethernet

Runs over Category 5 or higher UTP and uses all four wire pairs

50
Q

10GBaseT

A

Runes over four pairs of Category 6A or 7 UTP

Operates only in full-duplex mode (no hubs, only switches support 10GBaseT)

Still considered to be an expensive option

Good for network servers so they can keep up with desktop systems that commonly operate at 1 Gbps

51
Q

100BaseT4

A

Uses all 4 pairs of wires in UTP Category 3 cable

Obsolete

52
Q

1000BaseLX

A

Uses fiber-optic media

“L” stands for “long wavelength” laser

Supports a maximum cable segment of 5000 meters

53
Q

1000BaseSX

A

Uses fiber-optic media

“S” stands for “short wavelength laser

Can’t cover as long-wavelength lasers, but are less expensive

54
Q

1000BaseCX

A

Uses specially shielded, balanced, copper jumper cables

Might also be called “twinax” or “short-haul” copper cables

55
Q

10 Gigabit Ethernet IEEE 802.3ae

A

Much like the others in frame formats and media access

Defined to run only on fiber-optic cabling and specifies a maximum distance of 40 kilometers

Primarily used for network backbones

Varieties:
10GBaseSR, 10GBaseLR, 10GBaseER, 10GBaseSW, 10GBaseLW, 10GBaseEW

56
Q

40 Gigabit and 100 Gigabit Ethernet

A

Very high cost is still prohibitive

Adoption has been slow

Fiber-optic cabling is primary medium (although there are provisions to use special copper assemblies over short distances)

57
Q

Wireless Fidelity (Wi-Fi)

A

802.11 wireless network standard

is basically an extension to Ethernet (using airwaves instead of cabling as the medium)

58
Q

hotspot

A

public Wi-Fi network

59
Q

Two modes Wi-Fi can operate on:

A

Infrastructure (uses central access point)

Ad hoc (no central device, data travels from device to device like a bus)

60
Q

Two frequencies Wi-Fi operates at:

A

2.4 GHz and 5.0 GHz

Works like a tv channel, must tune to the correct channel to connect

61
Q

2.4 GHz Wi-Fi

A

actually 2.412 through 2.484 divided into 14 channels spaced 5MHz apart.

Needs 25 MHz to operate spanning 5 channels

62
Q

5.0 GHz

A

actually 4.915 through 5.825 GHz divided into 42 channels of 10, 20, or 40 MHz each

63
Q

Antenna

A

both a transmitter and a receiver on a Wi-Fi device.

Characteristics and placement determine how well a device transmits or receives Wi-Fi signals

usually categorized by their radiation patterns

64
Q

Omnidirectional antennas

A

signals radiate out from the antenna with equal strength in all directions

65
Q

Unidirectional antenna

A

signals are focused in a single direction (ideal for placement at one end of long, narrow spaces)

66
Q

Wi-Fi access method

A

Sending station can’t hear if another station begins transmitting so they cannot use the CSMA/CD access method that Ethernet uses

Wi-Fi devices use carrier sense multiple access with collision avoidance (CSMA/CA)

Uses request-to-send/clear-to-send (RTS/CTS) packets and acknowledgements

With this extra “chatter” actual throughput is essentially cut in half

67
Q

Common types of Wi-Fi signal interference

A

Absorption - solid objects absorb radio signals, causing them to attenuate (weaken)

Refraction - the bending of a radio signal as it passes from a medium or one density through a medium of a different density

Diffraction - the altering of a wave as it tries to bend around an object

Reflection - occurs when a signal hits a dense, reflective material, resulting in signal loss

Scattering - when a signal changes direction in unpredictable ways, causing a loss in signal strength

68
Q

Signal-to-noise ratio

A

the amount of noise compared with the signal strength (noise can come from equipment, other wireless devices, and other wireless networks)

69
Q

Throughput

A

the actual amount of data transferred (not counting errors and acknowledgements)

70
Q

Goodput

A

actual application-to-application data transfer speed

71
Q

Overhead

A

packet frame headers, acknowledgements, and retransmissions

72
Q

Encryption protocols

A

Wired equivalency privacy (WEP), Wi-Fi Protected Access (WPA), and WPA2

Not all devices support all three protocols, older devices may only support WEP and/or WPA

73
Q

Token Ring networks

A

Based on the IEEE 802.5 standard

Star physical topology, ring logical topology

A token is passed along a network and only the station with the token can transmit, frames are acknowledged and token is released, no collisions.

Originally operated at 4 Mbps and then increased to 16 Mbps and later 100Mbps

Uses cat 4 and higher UTP

Obsolete

74
Q

Fiber Distributed Data Interface Technology

A

Physical and Logical Ring topology

Uses a token-passing access method and dual rings for redundancy

Transmits at 100 Mbps and can include up to 500 nodes over a distance of 60 miles

Uses fiber-optic cable only

Obsolete on new networks

IT Networking Tech (8 decks)

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