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2.) communication and internet technologies - Coggle Diagram
2.) communication and internet technologies
data transmission
method
wireless
wireless (radio frequency)
infra red
fiber optic
speed of transmission
bandwidth - The amount of data that can be transmitted at one time is referred to.
different type of transmission
serial transmission
one signal
over a single wire
a very high transfer speed can be achieve
parallel transmission
number of wire
signal send simutanously
disadvantage
skew -
therefore, parallel transmission is good for short/small distance
make the data sent at a different speed (little)
crosstalk
wire are close to each other and may have electrical interference causing the data to be resent
data ribbon
example of parellel transmission
direction of transmission
three main way
half duplex
allow data to travel in both direction (cannot occur simutaneously) but can travel only one way at a time.
full duplex
half duplex + upgrade
travel in both direction at the same time (both direction simultaneously)
simplex transmission
allow data to be sent in one direction
error checking
causes
def: when data not arrive correctly
power surges
synchronisation issues
broken or damaged cables
electrical interference
can cause the bits to transpose (flip from 1 to 0 or 0 to 1) (sometime)
checking error :
parity checks
measure in
odd parity
adding the last number of 1 to the right (parity bit)
even parity
adding the last number of 0 to the right (parity bit)
how is it work
both parity will agree (either odd or even)
if its not match its clear that there is error
the parity bit may correct but other information may wrong so it is not a very good way to check eror
check digits
similiar to partiy
it is added number at the last digit
this case it is string (1-9)
how you do it?
you will be given the two long digit (weight and barcode) in a table
find the last digit of the barcode (first line)
find multiplication (time both number together) and use the last digit of the number
add multiplication together
find the last number by devided by 10 and findremainder
minus the remainder by 10 and the check digit (number 2) should be the same
check sums
similar to check digit but using string
process data through algorithm
produce "hash" code that is more than one digit long
e.g.
MD5
SHA1
used for downloading of software or the processing od credit card
how is it work
1.algorithm produce check sum
data/file sent recipient (receiver) and check sum
the recipient will run the data through the same algorithm to produce a check sum
the recipient will compare the checksum sented and produced if its match then it is safe (error free) if not they will have to redo everything again
ARQ
(automatic repeat request)
to ensure that both parties are aware of any error
simply system
how it works
1.time stting for data e.g. 10 seconds
data sent
if data receive within 10 secs the recipient (receiver) will sent back to tell them (acknowledge)
if not everything will be redo
the internet
protocol
about
set of rule to make internet work efficient and smooth operation
important protocal
TCP/IP
(transmission control protocol / internet protocol)
responsible data transmitted to internet - packet switching
HTTP/HTTPs
(Hyper Text transfer protocol)
IP
hardware
connect internet hardware is required
types of hardware
router
common is house holds
purpose for many devices to share one single internet connection
direct data from correct devices
modem
convert the digital signal of computer system into analogue signals that can travel across phone line
reduce error
network interface cards (NIC)
necessary for any device to be connected to network
provide physical or wireless connection
each has its own MAC some time 2 for wireless and wired connection
MAC addresses (media access control addresses)
assigned to every NIC by company that ,manufactured it
consist of 12 hexadecimal charecters
first 6 identify the manufaturer (creator) e.g. apple sony
last 6 (right side) identify the device itself
IP address can change but MAC address no change
HTML / CSS
general
def - The worlds largest network, it is a series of inter-connected networks (differ from WWW)
WWW (world wide web) - collection of web pages and can be accessed - a collection of web pages and documents that can be accessed via internet
ISP - internet services provider - company provide with internet
cookies
stored for client user the next time you visit website
small text file,
uses
storing personal information / data
remeber our login detail
save item in an online shopping basket
provided target advertisement (as it is can access our data) ??
storing payment detail
tracking our online habit (tracking our internet surfing habit)
warning
can have spyware and can read the content to the malware creator (hacker)
often advisable to not use cookie
very important
URL - uniform resource locator
pins the website you wish to visit
why (how they know how i wish)
section of website searched
3 main section
HTTPS://
protocol
www.bitsofbytes.co
Domain - web server's name
3.home.html
file name - file you try to receive from the web
extract from : HTTPS://WWW.BITSOFBYTES.CO/HOME.HTML
DNS (domain name server)
def: act as phone book internet
IP address: address given to every device connected to internet used to find correct server and connect to device or webpage
role :
the DNS will convert URL to IP address and direct to it when type URL and visit ISP
"the DNS will convert URL to IP address and direct to it when type URL and visit ISPwhen get visit URL to visit ISP (?) the DNS will convert URL to IP address and then direct traffic toward its"
store large list of URLs along + corresponding (?) IP addresses
security
malware
def: The umbrella term referring to any Malicious software (suspicious software that has intention to cause a disfunction to the users)
VIRUSES
-attached to file
after an activation it will replicate itself
it will jump to other memory file steal/ spam/ consuming user's file
TROJANS
https://www.google.com/url?sa=i&url=https%3A%2F%2Fsimple.wikipedia.org%2Fwiki%2FTrojan_horse_(computing)&psig=AOvVaw19lPzs7QfM9qMSJgkzlyHJ&ust=1615003620972000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCICMhLujmO8CFQAAAAAdAAAAABAO
trojan is act like trojan horse, it can activated (open) in form of little gift
they ALSO can perform various function of annoying to serious like VIRUS
WORMS
UNLIKE VIRUS it does not needed to attached to other file
once activated, it will REPLICATE themselves continuously until the computer CRASH from OVERLOADED.
can transfer by network , also
ADWARE
popup ADs - annoying
NOT harmful
SPYWARE
software that will gather your information
e.g. password, username, search
history
it will observe the user activity
RANSOMWARE
OR blackmail style threat
prevent user from playing
both use the hostage information for asking for money
Hackers
REASON
cause somebody harm
gain money
Fun - Some hackers enjoy the challenge
Reputation
Types of Hacker
White Hat Hackers
legal - hacking for good purpose e.g. to make sure the security is save
hack with permission
Grey Hat Hackers
fineline between being legal and illegal.
Black Hat Hackers
illegal - no permission to hack
does not have positive purpose e.g. hack for data for selling to gain money or as a hostage
botnet
large amount of computers that have been compromised by a hacker
used
DOS attack by all accessing a particular service (using bandwidth)
Commit click fraud
bot net computers offering the hacker PROTECTION
Spam email
ANTI - VIRUS SOFTWARE
protect yourself from hackers and malware AND KEEP IT UP TO DATE (malware can be invented)
work
the software contains a dictionary full of code SNIPPET taken from known malware
new file enter - the software will examine the file
the code will be compare to the known malware
if the code match the dictionary - the anti virus will delete or quarantine the file
if not - allow the computer to enter and run the file