how the internet works

Who co-created the internet

Vint Cerf and Bob Kahn

ARPANET

Advanced Research Projects Agency NETwork

Distributed or Centralized?

• Communication system between computers that would survive nuclear attack

• Messages sent through a giant mesh net, so that no one flaw of the system could stop the system

Who controls the internet?

• Many tiers of independent networks and service providers - meant to connect every device to every other device

Information transfer units

• bit = binary code (opposites)

• 8 bits =1 byte

• 1000 bytes =1 kilobyte

Types of Data Transfer

• Rate that the data is transferred = based on time (bandwidth is the maximum bit rate capacity - travel time is latency (how long it takes to get to the destination))

• Electricity (Copper wire - Ethernet)

  • Signal loss

  • Cheap

• Fibre Optics (Thread of glass engineered to reflect light)

  • No signal loss

  • Really fast

  • Connects continents

  • Expensive

  • Hard to work with

• Wirelessly (Radio)

  • Radio signals

  • Transfer information into waves of different frequencies

  • Signal loss

Protocol

A well known set of rules and standards used to communicate between machines

Device Address name

• Internet Protocol Address (IP)

• Hierarchy

  • 1973 + 1980s Each address has 32 bits (8 bits for each section)

  • 4 Billion addresses

  • Country

    • Region

      • Subnetwork

        • Device

• IPv6

  • 128 bits per address

  • 340 Undecillion addresses

Domain to address

• Domain Name System (DNS)

  • Looks for a domain name

  • Address is sent back to the computer

• Split up based on the .org, .com. .net to divide and conquer

DNS Spoofing

• Hacks into server and matches domain to impostor website

Packet system

• Rocket analogy - If you’re sending a large piece of information (or a big thing like a rocket) then you’ll need to send them all separately

• Routers determine fastest route between networks

  • Often takes into mind company relationships

  • Sends the routers through traffic managers at different times or out of order

• TCP - Transmission Control Protocol

  • Sends and receives data as packets and then ensures all packets are present. If not, the data will be resent

  • They are then rearranged once the packet makes its destination

URL Acronym

Universal Resource Locator

Computers talk to each other in the language

HTTP

• Hyper Text Transfer Protocol

• Get requests

Language to tell web browser how to make page

HTML - Hyper Text Markup Language

Why do images take time to load?

• They each require individual “GET” requests in order to load

What happens when you send information

HTTP “POST” request - sends information to the computer (data)

What are cookies?

ID numbers that your browser uses to remember who you are. This way, when you refresh or login to a page that has a “Remember me”, it remembers who you are

How do safe websites prevent snooping and tampering through communication

• Uses secure channel

  • Secure sockets layer

  • Transport Layer Security

• https = tttp + “Secure”

• Digital certificates verify that the website that you’re sending information to is actually the right website

  • Will warn you if the website doesn’t actually have a certificate

Scrambling and unscrambling

Encryption and decryption

Caesar’s cypher modification

Shifts each letter by a different amount, where the key is a list of numbers
- 10 digit encryption would mean 10 billion possible solutions, whereas 1 digit would be like 26
- Longer keys make it less likely to be computed in a small amount of time

Symmetric encryption

The sender and receiver have the same key, and both have private access to it - requires agreement between parties (which cannot always occur lol)

Asymmetric encryption

One device has keys for encrypting data, and another has keys for decrypting data

How does a virus work

• downloads through a program with or without permission

• may spread to other computers

• may lead to remote operation, controlling of programs, or delete files

DDoS

Distributed denial of service

• when many devices (through hackers) use software to attack and take down websites

Phishing

• Email asks you to log into an account on a website. If you log in, you give the fake website your password and username

How often does a human mistake cause hacking

90% of the time

How does a search engine work

• Searches are pre-prepared, constantly scanning the web in advance of any searches you might make

• Spider crawls through the web of links on the internet and records all of their information - adding it to a search index

• Each word looks through a search index, giving many results

  • Search engine ranks pages based on what it thinks you’re looking for. Sequencing, titling, and references to the page are all considered.

• Spammers sometimes artificially try to place themselves at the top of the search

• Note: distinction between homophones/homonyms/homographs

  • Machine learning (pitcher vs. pitcher)