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NETF > TUTORIAL 1 - Network Topologies & Technologies > Flashcards

TUTORIAL 1 - Network Topologies & Technologies Flashcards

1
Q

define topology

A

describes lay of land

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2
Q

define network topology

A

describes how network physically laid out & how signals travel from 1 device to another

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3
Q

what are the 2 categories of topologies and why are they categorized

A

physical and logical

physical layout of devices & cables doesn’t describe how signals travel from 1 device to another

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4
Q

what is a physical topology?

A

arrangement of cabling & how cables connect 1 device to another in network

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5
Q

what are the different types of physical topologies

A

bus
star
ring
meshed
point-t-point

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6
Q

what are the strengths of the physical bus topology

A

Strengths:

simplest & at 1 time most common method for connecting pc

continuous length of cable connecting 1 pc to another in daisy-chain fashion

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7
Q

what are the weaknesses of the physical bus topology

A

weaknesses:

limit of 30 pc per cable segment

max total length of cabling is 185m

both ends must be terminated if not will over circuit & signal bounce

any break in bus brings down entire network

adding/removing machine brings down entire network temporarily

limited to 10mbps half-duplex

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8
Q

how does data travel in a physical bus

A
  1. electrical pulses (signals) travel cable’s length in all directions
  2. signal travels across medium & from device to device (signal propagation)
  3. signal continues until weakened/absorbed by terminator
  4. if not terminated, signal bounces/reflected at end of medium
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9
Q

what is a physical star topology

A

uses central device for monitoring & managing network

central device is usually hubs & switches which can collects stats about network traffic patterns & detect errors

with cabling & NICs support, star network can be updated by replacing central device of higher speed if needed
Eg. 100mbps to 1gbps

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10
Q

what are the strengths of a physical star topology

A

faster than bus

centralized monitoring & management of network traffic possible

easier network upgrades

when num of workstations you need exceed num of ports on central device you simply add another central device

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11
Q

what is an extended star topology and what is the other name for it

A

when num of workstations have exceeded and several central devices are added, extended star is formed

hierarchical star

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12
Q

how does data travel 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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13
Q

what is a physical ring topology

A

similar to bus
devices are daisy-chained

no terminator, cabling brought around from last device back to 1st to form ring

most widely used to connect LANs with tech called Fiber Distributed Data Interface (FDDI)

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14
Q

what is a FDDI dual ring

A

FDDI acts as a high speed backbone to connect LANS (servers, switches) and terminal concentrators (which connects terminals)

uses dual ring which allows data to travel in both directions

1 ring failure doesn’t break network

operates using fiber-optic cable at 100mbps

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15
Q

what is a point-to-point topology (PMP)

A

it is also known as point-to-multipoint topology

all communication goes through central device

central device can communicate with 2 or more other devices

data travels on a dedicated link.

single connection made from router to switching device that directs traffic to correct branch office

mostly used in WANs where main office has connections to several branch offices via router

can connect 2 LANs separated by highway, river or railway tracks to make a wireless bridge

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16
Q

what is a mesh topology

A

connects each device to every other device in network

has multiple pt to pt connections for purposes of redundancy & fault tolerance

purpose is to ensure if 1 or more connections fail, there’s still path for reaching all devices on network

expensive due to multiple interfaces & cabling

found in large WANs & internetworks

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17
Q

what is a logical topology

A

describes how data travels from pc to pc

sometimes may be similar to physical arrangement of cables (bus, star, ring)

in a switched topology, there is always an electrical connection between the computer & switch

but when no data being transferred, there is no logical connection/circuit between devices

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18
Q

what is a network technology, what are some other terms for it and provide some examples

A

defines frame format & media

a method NIC uses to access the medium & send data frames
(either ethernet, token ring, wireless or a combination)

other terms:
network interface layer technologies

network architectures

data link layer technologies

examples:

LAN
ethernet
802.11 wireless
token ring

WAN
frame relay
FDDI
ATM

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19
Q

what are the 3 types of cables

A
  1. Unshielded Twisted Pair (UTP)

most common media type in LANs

consists of 4 pairs of copper wires twisted tgt

comes in numbered categories

sub-categories of UTP:
CAT3, CAT5, CAT6, CAT6a, CAT7

  1. fiber-optic cabling

uses twin strands of glass to carry pulses of light long distances & at high data rates

  1. coaxial- cabling

obsolete but used as network medium for Internet access via cable modem

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20
Q

what is baseband and broadband signaling

A

network technologies can use media to transmit signals in these 2 ways

21
Q

what is baseband signaling

A

sends digital signals in each bit of data represented by a pulse of electricity/light

sent at single fixed frequency & no other frames can be sent along with it

no more than 1 frame can be sent at same time

22
Q

what is broadband signaling

A

uses analogue techniques to encode binary 1s & 0s across a continuous range of values

signals flow at particular frequency & each frequency represents a channel of data

can have several transmissions occurring at same time

23
Q

what is an ethernet network and what range of speeds does it have

A

it is a LAN tech which is easy to install and is also a baseband.

range of speeds: 10 mbps to 10 gbps

operates in physical bus/star and logical bus/switched topology.

has same underlying tech as most NICs and hubs

24
Q

what is ethernet addressing

A

every station has a MAC address,

MAC address: 48 bits expressed as 12 hex digits

incoming frames must match NIC’s address/broadcast address (FF-FF-FF-FF-FF-FF)

once processed by NIC, incoming frames sent to network protocol for further processing

25
Q

what are ethernet frames, give example and frame conditions

A

there are 4 frame types, depending on network protocol used to send frame

frames must be between 64 & 1518 bytes in order to have pause in between transfers and receive other packets
- destination MAC
- source MAC
- type: network protocol
- data
- FCS: error handling check

example:
ethernet II frame is used by TCP/IP which is a network protocol

26
Q

what is ethernet media access

A

media access method:
rules governing how & when medium can be accessed for transmission

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

this is only used in a hub(switches that have switching tables)

Carrier Sense: listen before send
- must hear silence

Multiple Access: if 2 or more stations hear silence, multiple stations ma transmit at same time

Collision Detection: if 2 or more stations transmit, a collision occurs & is detected by NIC

all stations & servers wait for a random amount of time before retransmitting

all stations must retransmit

27
Q

what are collisions and collision domains and what are the conditions for it to occur

A

all devices interconnected by 1 or more hubs hear all signals generated by other devices

usually happens in half-duplex

only during full-duplex mode, (switches) will not have collisions because they have switching tables

collision domain:
extent to which signals in Ethernet bus topology network propagated

all devices in collision domain subject to possibility that whenever a device sends a frame, a collision might occur

more collisions > need retransmit > slower network traffic

28
Q

what is ethernet error handling, describe how and what ethernet uses to detects errors

A

ethernet is best-effort delivery system

there will be no acknowledgement whether data gets to destination

network protocols & apps ensure delivery

only collisions will be auto retransmitted

ethernet detects damaged frames using:

error-checking code in frame’s trailer called Cyclic Redundancy Check (CRC)

CRC determines if data is unchanged

if frame detected as damaged, its discarded with no notification

29
Q

half-duplex VS full-duplex communication

A

half-duplex
- can talk & listen but not both at the same time (2 way radio)

ethernet on hubs work in half-duplex

full-duplex means NIC/switch can transmit/receive simultaneously

CSMA/CD turned off

most switches operate in full-duplex

30
Q

define ethernet standards

A

they are expressed as XBaseY
X: speed
Y: type of media

T = twisted pair
FX = fiber optic

e.g 100BaseFX
100 = speed
Base = baseband(signal) is digital
FX = fiber optic

31
Q

what are the different types of standards (including obsolete ones)

A

100BaseT
100BaseTX
100BaseFX
100BaseT ethernet
100GBaseT ethernet
100BaseT4
1000BaseLX
1000BaseSX
1000BaseCX
10 Gigabit ethernet IEEE 802.3ae
40 Gigabit & 100 Gigabit ethernet

32
Q

decribe 100BaseTX

A

most common ethernet

category 5/higher UTP (cables)

use 2 of 4 wire pairs

2 types of 100BaseTX hubs

class I - can have >1 hub between devices

class II - can have max 2 hubs

switches can be used to connect many hubs

33
Q

describe 100BaseFX

A

runs over 2 strands of fiber optic

usually used as backbone cabling between
hubs/switches

also used when immunity to noise & eavesdroppng required

34
Q

describe 100BaseT ethernet

A

AKA Gigabit Ethernet
Category 5/higher UTP
use all 4 wire pairs

35
Q

describe 1000BaseLX

A

use fiber-optic media

“L” stands for “long
wavelength” laser

supports max cable length of 5000m

36
Q

describe 1000BaseSX

A

use fiber-optic media

“S” stands for “short wavelength” laser

not as long as long-wavelength lasers but less expensive

37
Q

describe 1000BaseCX

A

uses specially shielded, balanced, copper jumper cables

AKA “twinax”/”short-haul” copper cables

38
Q

describe 10 Gigabit Ethernet IEEE 802.3ae

A

similar to others in frame formats & media access

run only on fiber-optic

max 40km

primarily used for network backbones

varieties

10GBaseSR, 10GBaseLR, 10GBaseER, 10GBaseSW, 10GBaseLW, and 10GBaseEW

39
Q

describe 40 Gigabit & 100 Gigabit Ethernet

A

high cost

prohibitive

adoption slow

fiber optic primary medium

though have provisions to use special copper assemblies over short distance

40
Q

what is WI-FI and what medium does it use

A

802.11 Wi-Fi

AKA Wireless Fidelity (Wifi)

hotspot - public wifi network

is extension to ethernet

use airwaves instead of cabling as medium

41
Q

what are the modes of operation for WIFI

A

there are 2 modes

mostly focus on infrastructure

  1. infrastructure - u
    se central access point (AP)
  2. ad hoc - no central device

data travels from device to device like bus

AKA peer to peer mode

42
Q

what are the wifi channels and frequencies

A

operate at 2.4ghz or 5ghz (not fixed)

2.4ghz is actually 2.412 thru 2.484 divided into 14 channels spaced 5mhz apart

work like tv channel - must tune to channel to connect

needs 25mhz to operate spanning 5 channels

choose channels 5 apart from other known APs

5.0ghz actually 4.912 thru 5.825 ghz divided into 42 channels of 10, 20 or 40 mhz each

43
Q

what are wifi antennas

A

antennas are both transmitter & receiver

characteristics & placement determine how well device transmits/receives wifi signals

categorised by radiation pattern

  1. omnidirectional antennas

signal radiate out in equal strengths in all direction

  1. unidirectional antenna

signals focused in single direction

ideal for long, narrow spaces

44
Q

what are some access methods and operation

A

wifi access method

sending station can’t hear if another station begins
transmitting so cannot use CSMA/CD access method that ethernet uses

wifi device use carrier sense multiple access with collision avoidance (CSMA/CA)

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

extra handshake avoids collisions

with this extra “chatter” actual throughput cut in half

45
Q

what are the 9 signal characteristics

A
  1. absorption
  • solid objects absorb radio signals, causing them to attenuate (weaken)
  1. refraction
  • bending of radio signal as it passes from mediums of diff densities
  1. diffraction
  • altering of wave as it tries to bend around obj
  1. reflection
  • signal hits dense, reflective material resulting in signal loss
  1. scattering
  • signal changes dir in unpredictable ways causing loss in signal strength
  1. signal-to-noise ratio
  • amount of noise compared to signal strength
  • noise can come from eq, wireless devices, wireless networks etc
  1. throughput - actual amt of data transferred
  • not counting errors & acknowledgements
  1. goodput - actual app-to-app data transfer speed
  • overhead - packet frame headers, acks & retransmissions
46
Q

what are non-overlapping channels

A

Eg. 802.11b & g has 14 channels

1, 6, 11 are non-overlapping

2, 7, 12 are non-overlapping

4, 8, 13 are non-overlapping

47
Q

describe how wifi security works

A

signals can travel several hundred feet - wifi devices outside home/office can detect your signals

should be protected by encryption protocol that makes data difficult to interpret

encryption protocols

  1. wired equivalent privacy (WEP)
  2. Wifi protected access (WPA)
  3. WPA2

not all devices support all 3 protocols

older devices might only support WEP or/& WPA

48
Q

what are some token ring networks

A

based on IEEE 802.5 standard

token passed along network

only station with token can transmit

frame acknowledged & token released

no collisions

originally operated at 4mbps then increased to 16mbps & later 100mbps

uses category 4 & higher UTP

central device is Multi-Access Unit (MAU)

obsolete

49
Q

fiber distributed data interface technology

A

phy and logical ring topology

uses token-passing access method & dual rings for redundancy

transmits at 100mbps & can include up to 500 nodes over dist of 60miles

uses fiber-optic cable only

obsolete on new networks

NETF (3 decks)

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