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Networks and Internet - Coggle Diagram
Networks and Internet
HTTP & HTML
Website in computer: Computer talks to server (miles away), in miliseconds the computer asks server for website and server talks back to computer in HTTP
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HTML: Language to tell a web browser how to make a page look (font, image, text, etc)
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To send information to a web, your browser sends information in plain text to web server using HTTP post request
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Wires, cables & wifi: Binary sequences of 1's and 0's sent physically
Internet
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Bob Kahn and Vint Cerf, created the internet. It was the result of another experiment called the ARPANET. Which was a defense department research project
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Assures end-to-end connectivity of every part of the network. Utility of the net: any device can communicate with any other device
Nobody is in charge of the internet. There is no central control which decides how packets are routed or where pieces of network are built or who interconnects with who
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Completely open, connections shared & information sent in plain texts.
Hackers see information you send, yet, safe websites prevent this (browser communicates with a secure channel) by secure sockets layer (ssl) & transport layer security (tls)
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The Internet: Wires, Cables & Wifi
Internet ships binary information made out of bits (any pair of opposites. Ex: on & off, yes & no, etc)
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We physically send bits by electricity, light and radio waves
Send bits faster --> Bandwidth: Maximum transmission capacity of a device. Measured in Bit rate (number of bits that can be sent in a given time)
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Ethernet Wire: Measurable signal loss over just a few hundred feet.
Electricty --> (pro) Cheap, (con) Signal loss
Fiber optic cable (light): Thread of glass engineered to reflect light
Light --> (pro) really fast and no signal loss, (con) expensive and hard to work with (found across oceans)
Wireless (radio): Uses radio signals to send bits from one place to another
Radio --> (pro) totally mobile, (con) short range
Typically a 1 is used meaning on and a 0 meaning off. And because it has 2 states it is called binary code.
Today we send bits by electricity, light and radio waves.
Encryption & Public Keys
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Caesar Cipher: Algorithm that changes each letter in original message with a letter a certain number of steps down the alphabet. Easily to discover message
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Computers use Asymmetric Encryption (public key that can be exchanged with anybody and a private key that isn't shared)
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How Search Works
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Search Engine determines the best matches to your search to show your first (looks every single word from search separately)
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Spammers try to game the search algorithm to put their pages first as every time you visit a page the creator of the page gains money
Machine Learning: Artificial Intelligence, that lets computer learn without being explicitly programmed
IP Addresses & DNS
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In order for a new technology to use the internet, it needs to know which protocols to work with
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Addresses form part of one of the most important protocols used in the internet communication, the internet protocol (ip)
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DNS servers are connected in a distributed hierarchy, and are divided into zones splitting up responsability (.org, .com .net)
If one route is congested, data packets will go through other ones. May get to destination in different times and orders. Once they get to destination they are reassembled in order.
Data packets have multiple routes but choose the cheapest available path for each packet. Cheap = time.
Cybersecurity & Crime
Exploiting vulnerabilities in hardware software & unintentional decisions by people using software (stolen credit cards, social security numbers copromised, etc)
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Virus: Executable program that gets installed, usually unintentionally, and harms user and their computer. Can spread to other computers
Virus gets in computer by: lure a victim into installing a program with deception about the program's purpose, software on computer has a vulnerability, so attacker can install itself without permission
When virus is on computer it can steal or delete any of your files, control other programs, or allow someone else to control your computer
Hackers can take millions of computers worldwide and use them as digital army (botnet) to take down websites (DDOS)
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Phising Scam: When you get a "trustworthy email" asking to log in with your account, but clicking the email takes you to a fake website
Packets, Routing & Reliability
Information gets transferred from a computer to another by a path. The path can be fixed, yet it may change
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Having options for paths --> network fault tolerant.
Network can send packets even if something goes wrong.
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