Chap 2.1 - data transmission Flashcards by Amrita Rana

define data

info. translated for efficient transmission

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define transmission

-movement of data from 1 device to another

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define processing

-generating meaningful info.

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how is a text sent

-text
-converted into binary
-arranged into data packets / datagram
-router
-internet
-person

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define data packet

-data split into smaller bytes for transmission over a network
-contains header, payload, trailer

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standard size of data packets

-64 KiB

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what happens if data packet is small

-add 0’s

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are data packets unlimited

yes

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data packet structure for packet switching

-header
-payload
-trailer

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what is in a header

-IP address of source device
-IP address of destination device
-sequence of packet (packet no.)
-size of packet in bytes
-total no. packets
-IP of router
-hop no.

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what does sequence of data packet allow

correct reassembly of data packets

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what is in payload

-data

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what is in trailer

-method of identifying end of packet
-some form of error checking

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max hop count

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define packet switching

-forwarding packets form 1 router to another leading towards its destination

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difference btw packet & circuit switching

packet:
-no fixed route
-diff speed for each packets
-have to reorder at arrival
-less expensive
-packets travel independently
-don’t reserve bandwidth
circuit:
-dedicated pathway
-uniform delay of packets
-packets are in order
-more expensive
-packets travel in same path
-reserve entire bandwidth

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advantages for packet switching

-no single com. needed
-packet can be resent by rerouting if it fails = high speed transmission
-relatively easy to expand packet usage
-high data transmission rate possible

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disadvantages of packet switching

-can be lost & need to resend
-more prone to errors for real time streaming
-delay at destination = have to reassemble

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explain how packet switching works

-data is split into multiple packets
-each packet follows its own path to the destination
-routers determine the path
-rout is selected depending on no. packets in each router
-shortest path is selected

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define bouncing packets

-packets move back & forth btw routers & never reach destionation

what happens after max hops

-packet is destroyed & resent

explain problems caused by bouncing packets

network could stop because lost packets mount up and ‘clog’ the system

how is an email sent

-email is broken into packets
-IP source, IP destination, sequence no., packet size, total no. packets added to header
-router checks hop no. and IP destinations of packet & determines shortest path
-packets takes diff routes and arrive at diff times
-packets are checked for errors & reassembled according to sequence no.

which form of switching is more reliable

circuit, has dedicated channel

how are the delay btw packets in circuit switching

uniform delay

how does circuit switching work

Connection establishment: -all packets know entire path address -data processed at source system only -have fixed channel Data transfer: -delay btw packets is uniform -resource reservation = fixed path = more wastage Connection released

advantage of circuit switching

-dedicated pathway -packet arrive in order -no delay in transmission -Ideal for certain types of traffic

disadvantage of circuit switching

-inefficient resource utilisation -Delay when establishing channel -higher cost = fixed channel

eg of packet switching

-internet browsing -file download & upload -emails & instant messages

eg of circuit switching

-traditional cell phone call -Cellular voice call (Non-VoLTE) -dedicated fax lines

types of transmission mode

-simplex -half-duplex -full-duplex

types of data transmission

-serial -parallel

define simplex transmission mode

-data is sent from 1 direction eg. comp - printer, radio station - person, TV - person

define half-duplex transmission mode

-data is sent from 2 direction but not at same times eg. walkie - talkie

define full-duplex transmission mode

-data is sent from 2 directions at same time eg. messaging at same time, live call

define serial transmission

-data sent 1 bit at a time over a single channel eg. comp - printer via USB

define parallel transmission

-data sent in multiple bits over multiple channels eg. internal circuit in comp

diff btw serial & parallel transmissions

serial: -good over long distance -data sent in correct order -slower over short distance parallel: -good over short distance -data not sent in correct order -faster over short distance

what happens to data over long distance using parallel transmission

-parallel is better over short distance -data is skewed -longer the wire, more skewed

define USB

-Universal Serial Bus is a form of serial data transmission

what happens when device is plugged in comp

-comp. auto detect device from change in voltage in on data signal wire in USB cable -device is recognised & device driver software is loaded for com. -comp will look for device driver that match device. If not available, user is asked to download the software

advantages of USB

-devices plugged are auto detected & device drive is auto loaded up -connection only 1 way = prevent incorrect connection -is industry standard = considerable support available -support diff transmission rate -no need external power source -error-free transmission = USB protocol notify to re-transmit if error detected -backwards compatible -easy to use -high-speed data transmission

disadvantages of USB

-standard UBS support only 5m -some early UBs may not be supported by latest comp.s -slower data transfer rate than Ethernet

how much power does UBS cable supply

+5 V

USB types

-A -B -C -mini A -mini B -micro A -micro B -micro B super speed

diff wires in USB

-black -green -white -red

USB type C

-24 pin symmetrical connector -smaller than older UBS connectors -20V power connectivity = 10Gbps = support 4K video -backwards compatible

how can packet switching cause errors in vid & sound

-pic & sound not in sync = packets arrive at diff times -pauses in vid = time delay in assembling packets -degraded vid & sound = competing traffic on con. link -possible 'drop out' = packet take diff route & may get lost

note: -when drawing serial half/ full duplex, draw 2 line - dotted & undotted -be careful of which devices to use, eg need a web server