Question | Answer |
media | physical or atmospheric paths that signals follow |
transmit | issue signals along a network medium such as a cable |
transmission | process of transmitting or the progress of signals after they have transmitted |
signaling methods | analog digital |
volts | electrical current pressure |
strength of a signal | is directly proportional to its voltage |
transceiver | transmits and receives signals |
voltage | strength of a signal |
signals can be | current, light pulses, electromagnetic waves |
analog signal properties | amplitude frequency wavelength phase |
amplitude | height of the wave |
amplitude | measure of a waves strength at any given time |
frequency | number of times the amplitude cycles over fixed time |
wavelength | distance between one peak and the next |
phase | progress of wave over time in a relationship compared to a fixed point |
hertz | one full wave per second |
frequency expressed in | cycles per second |
hertz | cycles per second |
wavelength | distance between corresponding points on a wave cycle |
analog signal benefit | more variable than digital signals so they can convey greater subtleties with less energy |
analog signal drawback | voltage is varied and imprecise |
noise | any type of interference that may degrade a signal |
analog transmission | is more susceptible to transmission flaws |
digital signals | composed of pulses of precise,positive voltages and zero voltages |
one | pulse of positive voltages |
in a data signal | multiple bytes are combined to form a message |
eight bits | byte |
digital transmission involves | sending and receiving only a pattern of ones and zeros |
overhead | describes the nondata information that must accompany data for a signal to be properly routed and interpreted by a network |
examples of overhead | data link layer header and trailer |
examples of overhead | network layer addressing information |
examples of overhead | transport layer flow control information |
standards dictate | type of transmitter,communications channel,and receiver should be used |
modem | modulator demodulator |
data modulation | used to modify analog signals to make them suitable for carrying data over a communication path |
modulation | simple wave |
modulation | combined with another analog signal to produce a unique signal that gets transmitted from one node to another |
simple wave | carrier wave |
carrier wave | purpose is a messenger, help convey information |
data wave | information |
frequency modulation radio | data must travel along a particular frequency |
modulation | used to make a signal conform to a specific pathway |
am | a modulation technique in which the amplitude of the carrier signal is modified by the application of a data signal |
fm | a method of data modulation in which the frequency of the carrier signal is modified by the application of a data signal |
data transmission | direction in which the signals travel over the media |
simplex | signals travel in only one direction |
simplex | unidirectional communication |
digital drawback | many pulses required to transmit same information |
digital benefit | more reliable less noise interference |
overhead | required for proper signal routing and interpretation |
half duplex | signals travel in both directions but only one direction at a time |
half duplex | walkie talkie |
modem | accomplishes translation |
data modulation | make data suitable for carrying over communication path |
data modulation | data relies on digital transmission |
carrier wave | combined with another analog signal |
carrier wave | produces a unique signal |
carrier wave | purpose is to convey information |
information wave | data wave |
data wave | added to a carrier wave |
information wave | modifies one carrier wave property |
full duplex | bidirectional transmission |
full duplex transmission | telephone call |
full duplex transmission | ethernet networks because they use multiple channels on the same medium |
makes use of modulation | digital subscriber line |
channel | distinct communication path between nodes |
channels are seperated | physically and logically |
full duplex capability | increases the speed in which data travels over the network |
multiplexing | a form of transmission that allows multiple signals to travel simultaneously over one medium |
full duplex | signals travel in both directions simultaneously |
subchannels | the mediums channel is logically seperated into multiple smaller channels in order to carry multiple signals |
multiplexer | a device that can combine many signals on a channel |
channel | a lane on a highway.distinct way to communicate |
multiplexer | required at the transmitting end of a channel |
demultiplexer | at the receiving end |
physical seperation | one wire for transmission and one for reception |
demultiplexer | seperates the combined signals and regenerates them in their original form |
networks rely on multiplexing to | increase the amount of data that can be transmitted in any given time or span over a given bandwidth |
time division multiplexing | divides a channel into multiple intervals of time |
tdm | time slots |
subchannels | logical multiple smaller channels |
multiplexing | travel simultaneously over one medium |
mux | combines many signals |
demux | seperates combined signals |
tdm | assigns a seperate time slot to every node on the network,and,in that time slot,carries data from that node |
time slots | reserved for their designated nodes regardless of whetehr or not the node has data to transmit |
tdm | inefficient if the nodes on the network rarely send data |
statistical multiplexing | the transmitter assignes slots to nodes according to priority and need |
frequency division multiplexing | assigns a unique frequency band to each communications subchannel |
wavelength division multiplexing | technology used with fiber optic cable which enables one fiber optic connection to carry multiple light signals simultaneously |
dense wavelength division multiplexing | a multiplexing technique used over singlw mode or multimode fiber optic cable in which each signal is assigned a different wavelength for its carrier wave |
wavelength division multiplexing | a multiplexing technique in which each single on a fiber optic channel is assigned a different wavelength, which equates to its own subchannel |
analog | wave |
digital | block |
fdm | cell phones dsl |
point to point transmission | one transmitter and one receiver |
point to multipoint transmission | one transmitter and multiple receivers |
broadcast transmission | one transmitter and multiple undefined receivers |
nonbroadcast | one transmitter and multiple defined recipients |
broadcast transmission | simple and quick; used on wired and wireless networks |
important characteristics of data transmission | type of signaling and the direction in which it travels |
important characteristics of data transmission | number of senders and receivers;the relationship between them |
broadcast transmission | everyone can get the transmission whether or not they want it |
data communication may involve | a single transmitter with one or more receivers |
data communication may involve | multiple transmitters with one or more transceivers |
throughput | capacity ot bandwith |
throughput | amount of data transmitted during given time |
throughput | expressed as quantity of bits transmitted per second |
bandwidth | difference between highest and lowest frequencies medium can transmit |
bandwidth | range of frequencies |
bandwidth | measured in hertz |
bandwidth | the width of your frequency band |
baseband systems | can transmit only one signal ,or one channel,at a time |
baseband | transmission form in which digital signals are sent thru direct current pulses applied to the wire |
baseband | supports half duplex and full duplex |
broadband | form of transmission in which signals are modulated as radio frequency analog waves that use different frequency waves |
baseband | does not encode information as digital pulses |
broadband | more expensive because of extra hardware |
broadband | span longer didistances than baseband |
emi | common source of noise |
emi | waves that emanate from electrical devices or cables carrying electricity |
type of emi | radio frequency interference |
cross talk | a signal traveling on one wire or cable infringes on the signal traveling over an adjacent wire or cable |
alien cross talk | cross talk occurs between two cables |
next | near end cross talk |
attenuation | loss of a signals strength as it travels away from the source |
repeater | a device that regenerates a digital signal |
regeneration | process of retransmitting a digital signal,repeats the pure signal,with no noise |
latency | the delay between the transmission of a signal and its receipt |
affects latency | length of the cable and intervening connectivity device |
round trip time | length of time it takes for a packet to go from sender to receiver,then back from receiver to sender |
to constrain the latency and avoid its associated errors | each type of cabling is rated for a maximum number of connected network segments |
to constrain the latency and avoid its associated errors | each transmission method is assigned a maximum segment length |
throughput is limited | by the signaling and multiplexing techniques used in a given transmission method` |
baseband transmission | ethernet |
factors that affect the final cost in choosing to use a certain type of media | cost of installation |
factors that affect the final cost in choosing to use a certain type of media | cost of new system versus the old one |
factors that affect the final cost in choosing to use a certain type of media | maintenance and support |
factors that affect the final cost in choosing to use a certain type of media | cost of a lower transmission rate affecting productivity |
factors that affect the final cost in choosing to use a certain type of media | downtime |
near end cross talk | occurs near source |
type of media least affected by noise | fiber optic cable |
conduit | pipeline to contain and further protect cabling |
the maximum segment length depends on | attenuation, latency, maximum network length |
populated segment | part of a network that coontains end nodes |
unpopulated segment | link segment |
link segment | part of the network that does not contain end nodes but connects two networking devices such as routers |
maximum distance a signal can travel and still be interpreted | is equal to a segments length |
factors that determine the size and scalabiility of networking media | maximum nodes per segment |
factors that determine the size and scalabiility of networking media | maximum segment length |
factors that determine the size and scalabiility of networking media | maximum network length |
amplifiers and repeaters | found in the physical layer of the osi model |
repeater | device regenerates digital signals |
amplifier | boosts analog signals |
connectors | pieces of hardware that connects the wire to the network device |
media converter | hardware that enables networks or segments running on different media to interconnect and exchange signals |
physical media characteristics | throughput |
physical media characteristics | cost |
physical media characteristics | noise and immunity |
physical media characteristics | connectors and media converters |
causes of throughput limitation | laws of physics |
causes of throughput limitation | noise |
causes of throughput limitation | signaling and multiplexing techniques |
causes of throughput limitation | devices connected to transmission medium |
maximum nodes per segment dependency | attenuation and latency |
sheath | jacket |
attenuation | signal decaying over time |
latency | time back and forth |
sheath | protects the cable from physical damage |
because of its shielding | most coaxial cable has a high resistance to noise |
rg | radio guide |
significane difference between cable types | lie in the materials used for their shielding and conducting cores |
impedeance | resistance that contributes to controlling the signal |
impedance | expressed in ohms |
transmission characteristics | impedance attenuation throughput |
awg | american wire gauge |
coaxial cable | is used to guide radio frequencies in broadband transmission |
awg size | size of the conducting core in a coaxial cable |
coaxial cable is a central metal core | surrounded by insulator,braided metal sheilding,outer cover |
rg 6 | deliver broadband cable internet service and cable tv |
rg 6 | impedeance of 75 ohms and contains 18 awg conducting core |
coaxial cable advantage | carries signals farther before amplifier is required |
coaxial cable disadvantage over twisted pair | more expensive |
rg 8 | provided the medium for the first ethernet network |
rg 8 | impedeance of 50 ohms and contains 10 awg conducting core |
rg 58 | impedeance of 50 ohms and contains 24 awg conducting core |
rg 59 | impedeance of 75 ohms and contains a 20 or 24 awg conducting core |
rg 58 | popular medium for ethernet lans |
rg 59 | used for relatively short connections |
the larger the awg size | the smaller the diameter of a piece of wire |
types of connectors | f type and bnc |
twisted pair cable | inexpensive, flexible,easy to install,scommadates everal topologies,spans msignificant distance before requitring repeater |
twisted pair cable | accomodates several different topologies |
more wire twists per foot | more resistance to cross talk,higher quality,more expensive |
hundreds of different designs | twisted pait cable |
tia/eia 568 | wiring standard specification |
twisted pair categories | shielded and unshielded |
twisted pair categories | Cat 3,5,5e,6,6a,7 |
shielded twisted pair | individually shielded,each pair has a shield and then shielded as a whole |
unshielded twisted pair | used most often |
stp and utp | use registered jack 45 |
telephone connections | use registered jack 11 |
maximum segment length for stp and utp | 100 meters and 328 feet |
patch cable | relatively short cable and had connectors at both ends |
termination standards | tia/eia 568 a or b |
tia 568 a or tia 568 b | defines a patch or a crossover cable |
fiber optic cable | one or more glass or plastic fibers at its center core |
data transmission | pulsing light sent from laser or light emittting diode thru central fibers |
cladding | layer of glass or plastic surrounding core |
fiber optic cable benefits | high throughput, high resistance to noise, |
fiber optic cable benefits | excellent security,able to carry signals for a longer distance |
fiber optic drawbacks | more expensive and requires special equipment to splice and connect |
ferrule | short tube within a connector that encircles the fiber and keeps it properly aligned |
optical loss | degradation of the light signal after it travels a certain distance away from its source |
single mode fiber | consists of a narrow core of eight to ten microns in diameter |
single mode fiber | laser generated light travels over one path |
single mode fiber | light does not disperse as signal travels |
single mode fiber | can carry signals many miles |
multimode fiber | contains a core with a larger diameter than single mode fiber,usually fifty to 62.5 microns |
multimode fiber | many pulses of light generated by a laser or led traveling at different angles |
multimode fiber | greater attenuation than single mode fiber |
multimode fiber | not suited to distances longer then a few miles,it is less expensive |
fiber optic converter | required to connect multimode fiber networks to single mode fiber networks |
serial | refers to a style of data transmission in which the pulses that represent bits follow one another along a single transmission line |
serial | issued sequentially not simultaneously |
physical layer standard | specifies signal voltage,signal timing,plus the characteristics of compatible interfaces |
rs 232 | serial data transmission method |
rs 232 connectors | db9,db 25,rj 45 |
straight thru cable | connect two dissimiliar devices |
crossover cable | connect two similiar devices |
cable plant | hardware that make sup the enterprise cabling system |
tia/eia joint 568 commercial building wiring standard | structured cabling |
entranc facilities | designates where the telecommunications service provider accepts responsibility for the external connection |
demarc | their network stops and ours starts |
main distribution frame | first point of interconnection between an organizations LAN or WAN and a service providers facility |
mdf | computer room or equipment room |
cross connect facilities | the point where circuits interconnect with other circuits |
punch down block | panel of data recepors into which twisted pair wire is inserted,punched down,to complete a circuit |
intermediate distribution frame | junction point between the mdf and concentration of fewer connections |
backbone wiring | the cables or wireless links that provide interconnection between entrance facilities and mdfs,mdf,idfs and telecommunications closet |
telecommunications closet | contains connectivity for groups of connections in the area |
horizontal wiring | wiring that connects workstations to the closest telecommunications closet |
three possible cabling types for horizontal wiring | stp,utp or fiber optic cables |
maximum allowable distance for horizontal wiring | 100 meters |
work area | an area that encompasses all patch cables and horizontal wiring necesary to connect workstations,printers and other network devices from their nics to the telecommunications closet |
bend radius | the radius of the maximum arc into which you can loop a cable before you will impair data transmission |
plenum | the area above the ceiling tile or below the subflooring |
two methods for transmitting data | analog and digital |
tia/eia specifications for backbone cabling | utp single mode multi mode fiber |
many network problems can be traced to | poor cable installation |
multiplexing | allows multiple signals to travel simultaneously over one medium |
analog | signal wave |
digital | pulse,on off |
zip cord cable | short fiber optic cable in which two strands are arranged side by side in conjoined jackets,enabling full duplex communication |
console | the serial interface on the back of the connectivity device |
100 meters | 90 meters to telecommunications closet 10 meters to workstation |