ARPANET - Advanced Research Projects Agency Network
Types of Networks
Centralized
Distributed - a distributed packet-switched network
The internet is made up of an incredibly large number of independently operating networks
Completely independent, no central control on how packets are routed
Computing Device - a machine that can run a program, including computers, tablets, servers, routers, and smart sensors
Computing System - a group of computing devices and programs working together for a common purpose
Computer Network - a group of interconnected computing devices capable of sending or receiving data
Path - the series of connections between computing devices on a network starting with a sender and ending with a receiver
Bandwith - the maximum amount of data that can be sent in a fixed amount of time, usually measured in bits per second
In the 1970s, there was no standard method for networks to communicate
Vint Cert and Bob Kahn invented the Internetworking Protocol (the internet)
Internet Service Provider - ISP
The internet is really a design philosophy expressed in a set of protocols
Design philosophy is being used to adapt and absorb new communication technologies
Protocol - a well-known set of rules and standards used to communicate between machines (and specify the behavior of some systems)
All the different devices on the internet have unique addresses
An address on the internet is just a number that’s unique to each device on the network
Internet Protocol - IP
The computer’s address is called the IP address (the protocol for sending data across the Internet that assigns unique numbers to each connected device
Traditional IP addresses are 32 bits long, with 8 bits for each part of the address
The first part of the address identifies the country/network, then the region/network, then the subnetworks, and then the device address
It is the unique number assigned to each device
It is no longer countries and regions, it’s now networks and sub-networks
IPv4 - provides more than 4 billion unique addresses
IPv6 - 128 bits per address and 340 undecillion unique addresses
Domain Name System (DNS) - corresponds to the website domain with the IP address
DNS Servers are connected in a distributed hierarchy
DNS was created to be an open public communication protocol for government and educational institutions
the system responsible for translating domain names like example.com into IP addresses
DNA Spoofing - sending people to an imposter website
DNS and IP are designed to scale no matter how much the internet grows
Router - a type of computer that forwards data across a network
Redundancy - the inclusion of extra components so that a system can continue to work even if individual components fail, for example by having more than 1 path between any 2 connected devices in a network
Fault Tolerant - can continue to function even in the event of individual component failures. This is important because elements of complex systems like a computer network fail at unexpected times, often in groups
User Datagram Protocol (UDP)
Main Idea: Like Protocol 1 or clearing out the library as fast as you can, the goal is to send information quickly without worrying about accuracy.
Basics of how it works: Send all the packets but don’t check if they get through or arrive in the right order.
Use in real life: Useful when split seconds matter more than correcting errors, like video conferencing, live streaming, and online gaming.
Summary: a protocol for sending packets quickly with minimal error-checking and no resending of dropped packets
Transmission Control Protocol (TCP)
Main Idea: Like Protocol 2 or numbering every book in the library. It’s slower but more accurate.
Basics of how it works: Number packets so they can be re-ordered, confirm all were received, and resend any missing packets. Multiple back-and-forth confirmations between sender and receiver.
Use in real life: Useful when accuracy matters more than saving a split second, like sending emails, photos, or just browsing websites.
TCP - manages the sending and receiving of all your data as packets
Direct dedicated connections - impossible to keep things working
Data travels on the internet in a much less direct fashion
The information does not need to follow a fixed path
They send in packets of information
Many kinds of digital information can be sent with IP packets
Packets have the address of where they came from and where it is going
Routers (or computing devices) act like traffic managers to keep packets moving smoothly and packets are reassembled in order
However, packets may arrive at different times or orders
Routers choose the cheapest available path for each piece of data
“Cheapest” - time, politics, relationships
Often the best route for data to travel isn’t the most direct
TCP + Router systems - scalable
Grow and scale the internet without interrupting service
Principles of fault tolerance and redundancy, more routers = more reliable
Different systems that make up the internet connect, communicate with each other, and collaborate because of agreed-upon standards for how data is sent around the internet
Datastream - information passed through the internet in packets
Packet Metadata - data added to packets to help route them through the network and reassemble the original message
Packet - a chunk of data sent over a network. Larger messages are divided into packets that may arrive at the destination in order, out-of-order, or not at all
URL - Uniform Resource Locator
HTTP - HyperText Transfer Protocol
the language used to communicate between web browsers and servers
“Get” requests
Send information (in a form or search query)
a protocol for computers to request and share the pages that make up the world wide web on the Internet
HTML - HyperText Markup Language
Cookies - what websites use to remember who you are (an ID number that remembers you)
The internet…
is completely open
the connections are shared
and information is sent in plain text
Safe websites prevent snooping & tampering by communicating on a secure channel
Secure Sockets Layer (SSL) & its successor, Transport Layer Security (TLS) are a layer of security wrapper around your communications
They are active when there is a lock in the address bar, next to the HTTPS
The HTTPS protocols make sure the HTTP requests are secured and protected
Digital certificate - ID card proving that it is the website that it claims to be, which is published by
Certificate authorities - trusted entities that verify the identities of websites and issue certificates for them
Browser will warn you if there is not a proper certificate
HTTP & DNS manage the sending & receiving of web files
TCP/IP & Routing that break down and transport packets
Wires, cables & WiFi are made using binary sequences of 1’s and 0’s that are sent physically
Scalability - the capacity for the system to change in size and scale to meet new demands
World Wide Web - a system of linked pages, programs, and files
The World Wide Web is different from the Internet. The World Wide Web are files, web pages, and media. The Internet is the network we use to access those files.
The DNS is an important system in helping the Internet scale.
Digital Divide - differing access to computing devices and the Internet, based on socioeconomic, geographic, or demographic characteristics
Can affect both individuals and groups
Raises ethical concerns of equity, access, and influence globally and locally
Affected by the actions of individuals, organizations, and governments