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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
what are ethernet frames, give example and frame conditions
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
what is ethernet media access
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
what are collisions and collision domains and what are the conditions for it to occur
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
what is ethernet error handling, describe how and what ethernet uses to detects errors
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
half-duplex VS full-duplex communication
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
define ethernet standards
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
what are the different types of standards (including obsolete ones)
100BaseT 100BaseTX 100BaseFX 100BaseT ethernet 100GBaseT ethernet 100BaseT4 1000BaseLX 1000BaseSX 1000BaseCX 10 Gigabit ethernet IEEE 802.3ae 40 Gigabit & 100 Gigabit ethernet
32
decribe 100BaseTX
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
describe 100BaseFX
runs over 2 strands of fiber optic usually used as backbone cabling between hubs/switches also used when immunity to noise & eavesdroppng required
34
describe 100BaseT ethernet
AKA Gigabit Ethernet Category 5/higher UTP use all 4 wire pairs
35
describe 1000BaseLX
use fiber-optic media "L" stands for "long wavelength" laser supports max cable length of 5000m
36
describe 1000BaseSX
use fiber-optic media "S" stands for "short wavelength" laser not as long as long-wavelength lasers but less expensive
37
describe 1000BaseCX
uses specially shielded, balanced, copper jumper cables AKA "twinax"/"short-haul" copper cables
38
describe 10 Gigabit Ethernet IEEE 802.3ae
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
describe 40 Gigabit & 100 Gigabit Ethernet
high cost prohibitive adoption slow fiber optic primary medium though have provisions to use special copper assemblies over short distance
40
what is WI-FI and what medium does it use
802.11 Wi-Fi AKA Wireless Fidelity (Wifi) hotspot - public wifi network is extension to ethernet use airwaves instead of cabling as medium
41
what are the modes of operation for WIFI
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
what are the wifi channels and frequencies
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
what are wifi antennas
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 2. unidirectional antenna signals focused in single direction ideal for long, narrow spaces
44
what are some access methods and operation
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
what are the 9 signal characteristics
1. absorption - solid objects absorb radio signals, causing them to attenuate (weaken) 2. refraction - bending of radio signal as it passes from mediums of diff densities 3. diffraction - altering of wave as it tries to bend around obj 4. reflection - signal hits dense, reflective material resulting in signal loss 5. scattering - signal changes dir in unpredictable ways causing loss in signal strength 6. signal-to-noise ratio - amount of noise compared to signal strength - noise can come from eq, wireless devices, wireless networks etc 7. throughput - actual amt of data transferred - not counting errors & acknowledgements 8. goodput - actual app-to-app data transfer speed - overhead - packet frame headers, acks & retransmissions
46
what are non-overlapping channels
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
describe how wifi security works
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
what are some token ring networks
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
fiber distributed data interface technology
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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