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Unit 2: The Internet

  • 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

  • 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