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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
LAN examples of Network technologies
Ethernet 802.11 wireless Token Ring
26
WAN examples of network techonologies
Frame Relay FDDI ATM
27
Unshielded Twisted Pair (UTP)
most common media type in LANs Consists of 4 pairs of copper wires each twisted together Comes in numbered categories
28
Fiber-optic cabling
uses thin strands of glass to carry pulses of light long distances and at high data rates
29
Coaxial cable
obsolete as a LAN medium but is used as the network medium for internet access via a cable modem
30
Two main ways network technologies can use media to transmit signals:
Baseband or Broadband
31
Baseband
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
Broadband
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
Ethernet
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
Ethernet addressing
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
Media access method
Rules governing how and when the medium can be accessed for transmission
36
Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
ethernet uses this
37
Carrier Sense
Listen before sending (must hear silence)
38
Multiple Access
If two or more stations hear silence, multiple stations may transmit at the same time
39
Collision Detection
If two or more stations transmit, a collision occurs and is detected by the NIC, all stations must retransmit
40
Collision domain
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
Cyclic Redundancy Check (CRC)
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
Half-duplex
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
Full-duplex
means NIC/switch can transmit and receive simultaneously (like a telephone) CSMA/CD is turned off Most switches operate in full-duplex
44
Ethernet Standards representation
XBaseY X - designates the speed of transmission Y - specifies the type of media (T - twisted pair, FX - fiber optic)
45
10BaseT
Uses two of the four wire pairs Runs over Category 3 or higher UTP cabling Highly susceptible to collisions and is obsolete
46
100BaseTX
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
Two types of 100BaseTX hubs:
Class 1 - can have only one hub between communicating devices Class 2 - can have a maximum of two hubs between devices
48
100BaseFX
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
1000BaseT
Also known as Gigabit Ethernet Runs over Category 5 or higher UTP and uses all four wire pairs
50
10GBaseT
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
100BaseT4
Uses all 4 pairs of wires in UTP Category 3 cable Obsolete
52
1000BaseLX
Uses fiber-optic media "L" stands for "long wavelength" laser Supports a maximum cable segment of 5000 meters
53
1000BaseSX
Uses fiber-optic media "S" stands for "short wavelength laser Can't cover as long-wavelength lasers, but are less expensive
54
1000BaseCX
Uses specially shielded, balanced, copper jumper cables Might also be called "twinax" or "short-haul" copper cables
55
10 Gigabit Ethernet IEEE 802.3ae
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
40 Gigabit and 100 Gigabit Ethernet
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
Wireless Fidelity (Wi-Fi)
802.11 wireless network standard is basically an extension to Ethernet (using airwaves instead of cabling as the medium)
58
hotspot
public Wi-Fi network
59
Two modes Wi-Fi can operate on:
Infrastructure (uses central access point) Ad hoc (no central device, data travels from device to device like a bus)
60
Two frequencies Wi-Fi operates at:
2.4 GHz and 5.0 GHz Works like a tv channel, must tune to the correct channel to connect
61
2.4 GHz Wi-Fi
actually 2.412 through 2.484 divided into 14 channels spaced 5MHz apart. Needs 25 MHz to operate spanning 5 channels
62
5.0 GHz
actually 4.915 through 5.825 GHz divided into 42 channels of 10, 20, or 40 MHz each
63
Antenna
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
Omnidirectional antennas
signals radiate out from the antenna with equal strength in all directions
65
Unidirectional antenna
signals are focused in a single direction (ideal for placement at one end of long, narrow spaces)
66
Wi-Fi access method
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
Common types of Wi-Fi signal interference
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
Signal-to-noise ratio
the amount of noise compared with the signal strength (noise can come from equipment, other wireless devices, and other wireless networks)
69
Throughput
the actual amount of data transferred (not counting errors and acknowledgements)
70
Goodput
actual application-to-application data transfer speed
71
Overhead
packet frame headers, acknowledgements, and retransmissions
72
Encryption protocols
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
Token Ring networks
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
Fiber Distributed Data Interface Technology
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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