Transcript How the Internet Works

HOW THE INTERNET WORKS
HTTPS://WWW.KHANACADEMY.ORG/COMPUTING/COMPUTERSCIENCE/INTERNET-INTRO
WIRES, CABLES, & WIFI
• HTTPS://WWW.KHANACADEMY.ORG/COMPUTING/COMPUTER-SCIENCE/INTERNET-INTRO
WIRES, CABLES, & WIFI
•THE INTERNET: A
PHYSICAL SYSTEM
MADE TO MOVE
INFORMATION
THE INFORMATION IS MADE OF BITS
• BIT=ANY PAIR OF OPPOSITES (0N/OFF)
• ON=1
• OFF=0
• 8 BITS=1BYTE
• BINARY
INTERNET SPEED
• BANDWIDTH: TRANSMISSION
CAPACITY
• BITRATE : THE NUMBER OF BITS
PER SECOND A SYSTEM CAN
TRANSMIT
• LATENCY : TIME IT TAKES FOR A
BIT TO TRAVEL FROM THE
SENDER TO THE RECEIVER
CABLES
• ETHERNET WIRE-SENDS
INFORMATION USING
ELECTRICITY
• LOSES SIGNAL OVER LONG
DISTANCES
• FIBER OPTIC-SENDS
INFORMATION AS LIGHT
• NO SIGNAL LOSS OVER
DISTANCES
WIFI
• WIRELESS-USES RADIO SIGNALS TO
TRANSMIT INFORMATION
• ROUTER RECEIVES INFORMATION AND
THEN TRANSLATES THAT INFORMATION
FROM BINARY INTO RADIO WAVES
THAT ARE BROADCAST AND YOUR
COMPUTER OR SMARTPHONE CAN PICK
UP
• SIGNAL LOSS OVER LONG DISTANCES.
IP ADDRESSES AND DNS
• HTTPS://WWW.KHANACADEMY.ORG/COMPUTING/COMPUTER-SCIENCE/INTERNET-INTRO
THE INTERNET IS A NETWORK OF NETWORKS
• LINKS BILLIONS OF DEVICES TOGETHER AROUND THE
GLOBE
• ISP : INTERNET SERVICE PROVIDER
• PROTOCOL : A SET OF RULES AND STANDARDS USED TO
COMMUNICATE BETWEEN MACHINES
ALL DEVICES ON THE INTERNET HAVE AN UNIQUE
ADDRESS
• IP (INTERNET PROTOCOL) ADDRESS : THE COMPUTER
SENDS A MESSAGE TO ANOTHER COMPUTER WITH ITS
ADDRESS (A SPECIFIC NUMBER THAT INDICATES ITS
LOCATION)
• DNS (DOMAIN NAME SYSTEM) : ASSOCIATES NAMES WITH
THE CORRESPONDING ADDRESS. THE COMPUTER USES THE
DNS TO FIND THE IP ADDRESS
PACKETS, ROUTING, AND RELIABILITY
• HTTPS://WWW.KHANACADEMY.ORG/COMPUTING/COMPUTER-SCIENCE/INTERNET-INTRO
DATA TRAVELS ON THE INTERNET INDIRECTLY-THERE IS
NOT A FIXED PATH FROM ONE COMPUTER TO
ANOTHER
INFORMATION TRAVELS ON THE INTERNET IN A
PACKET
A PACKET TRAVELS ONE PLACE TO ANOTHER ON THE
INTERNET A LOT LIKE HOW YOU MIGHT GET FROM ONE
PLACE TO ANOTHER IN A CAR, DEPENDING ON TRAFFIC OR
ROAD CONDITIONS.
PACKETS CAN BE DIVIDED INTO SMALLER PACKETS IF THE
INFORMATION TO BE SENT IS TOO BIG. EACH SMALLER
PACKET CONTAINS THE DESTINATION ADDRESS TO IT GETS
TO THE RIGHT PLACE
ROUTER- ACTS AS A TRAFFIC MANAGER TO KEEP THE
PACKETS MOVING SMOOTHLY
EACH ROUTER KEEPS TRACK OF THE DIFFERENT
ROUTES FOR SENDING PACKETS AND CHOOSES THE
CHEAPEST AVAILABLE PATH FOR EACH PIECE OF DATA
BASED ON DESTINATION IP ADDRESS.
HAVING OPTIONS FOR PATHS MAKES THE NETWORK
FAULT TOLERANT-WHICH MEANS THE NETWORK CAN
KEEP SENDING PACKETS EVEN IF SOMETHING GOES
HORRIBLY WRONG. THIS HELPS MAKE THE INTERNET
RELIABLE
TCP (TRANSMISSION CONTROL PROTOCOL) :
MANAGES THE SENDING AND RECEIVING OF ALL
YOUR DATA PACKETS
HTTP AND HTML
• HTTPS://WWW.KHANACADEMY.ORG/COMPUTING/COMPUTER-SCIENCE/INTERNET-INTRO
URL (UNIFORM RESOURCE LOCATOR) : A WEBSITES
ADDRESS
HTTP (HYPER TEXT TRANSFER PROTOCOL) : THE
LANGUAGE USED TO COMMUNICATE BETWEEN WEB
BROWSERS AND SERVERS
• MANAGE THE SENDING AND RECEIVING OF WEB FILES
HTML (HYPER TEXT MARKUP LANGUAGE) : THE
LANGUAGE THAT TELLS THE WEB BROWSER HOW
THE PAGE SHOULD LOOK
COOKIES: AN ID NUMBER A WEBSITE USES TO
REMEMBER WHO YOU ARE
ENCRYPTION & PUBLIC KEYS
• HTTPS://WWW.KHANACADEMY.ORG/COMPUTING/COMPUTER-SCIENCE/INTERNET-INTRO
THE INTERNET IS AN OPEN AND PUBLIC SYSTEM
WHICH MAKES IT VULNERABLE TO HACKING
• ENCRYPTION: SCRAMBLING OR CHANGING A
MESSAGE TO HIDE IT.
• DECRYPTION: UNSCRAMBLING THE MESSAGE TO
MAKE IT READABLE
• KEY: A SECRET PASSWORD FOR UNLOCKING A
MESSAGE
ASYMMETRIC ENCRYPTION: DIFFERENT KEYS FOR
ENCRYPTING AND DECRYPTING DATA
• PUBLIC KEY-SHARED WITH EVERYBODY SO
ANYBODY CAN ENCRYPT A MESSAGE
• PRIVATE KEY-CAN ONLY BE DECRYPTED BY A
COMPUTER WITH ACCESS-ONLY YOU CAN
DECRYPT THE MESSAGE
HTTPS : SECURED
CYBERSECURITY AND CRIME
• HTTPS://WWW.KHANACADEMY.ORG/COMPUTING/COMPUTER-SCIENCE/INTERNET-INTRO
VIRUS IS A PROGRAM THAT GETS INSTALLED (USUALLY
UNINTENTIONALLY) AND HARMS THE USER AND COMPUTER.
CAN SPREAD TO OTHER COMPUTERS.
HOW DOES A VIRUS INFECT?
1. TRICK THE USER TO INSTALL A PROGRAM THAT
CONTAINS THE VIRUS.
2. SOFTWARE HAS A VULNERABILITY-GET IN A BACK DOOR.
ONCE IN, IT CAN STEAL OR DELETE FILES, CONTROL
PROGRAMS, OR ALLOW REMOTE OPERATION.
SPAM/PHISHING : EMAIL TRICK TO GET PEOPLE TO
SHARE SENSITIVE PERSONAL INFORMATION
AVOID GETTING HACKED
1. USE STRONG PASSWORDS
2. CHECK FOR AUTHENTIC WEB ADDRESSES
3. INSTALL SYSTEM SECURITY UPDATES OFTEN
4. DON’T INSTALL SOFTWARE YOU DON’T TRUST.