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What is the internet?
A philosophy of making information and knowledge open and accessible to ALL, a network of networks, built on open, agreed upon protocols.
A way for all machines and humans to communicate with each other.
What is a computing device?
A physical artifact that can run a program.
What is bandwidth?
What is latency?
BANDWIDTH: The capacity of data transfer in a system. Measure by bitrate (the number of bits a system can send per second).
LATENCY: The time it takes for a bit to get from sender to receiver. Low latency = fast connection.
What is DNS?
Domain Name System
Translates names to IP Addresses
DNS is Scalable: the hierarchy helps the system scale - each layer is only in charge of a small amount of information, easy to add a single element to a layer, easy to add a new layer, searching one layer is much easier than searching every possible domain.
What is fault tolerance?
Multiple paths exist between two points. Individual routers can break and the system will still work fine. This improves reliability.
This makes the routing system scalable.
What is a protocol?
A widely agreed upon set of rules that standardize communication between machines.
What is an input device?
What is an output device?
What are storage devices?
What are network devices?
INPUT: Computing devices that are used to take in information from a user or another device.
OUTPUT: Computing devices that are used to send computer data to the user.
STORAGE: Computing devices that remember information.
NETWORK: Computing devices that are used for communication between computers.
What is an internet address?
Every device on the internet has a unique internet address, data has a to and from address, addresses follow a standard, agreed upon format.
From Name to IP Steps
2. Ask a Root Server
3. Ask a TLD Server
4. Ask a Hosting Server
5. Save in the CACHE
6. Send the request
What is a packet?
All data sent over the internet is broken down into several packets. Packets are the units of data that are sent over the network. Once packets arrive they are pieced together. The layout of the packet is defined by protocol.
Packets are labeled with metadata.
All packets must have a destination IP Address, a from IP Address, the actual data being sent.
The Internet Protocol gives each device on a network an IP Address and defines the layout of a single packet.
Transmission Control Protocol (TCP) is a protocol that allows for sending multiple packets between two computers. TCP checks that all packets arrived and that they can be put back together in the proper order.
What impact has the internet had?
Collaboration, Communication (dissemination of information), crowdsourcing, anonymity, censorship.
What is a computing system?
What is a computing network?
SYSTEM: A group of computing devices and programs working together for a common purpose.
NETWORK: A group of interconnected computing devices capable of sending/receiving data. Also a type of computing system.
What is an Internet Protocol (IP)?
A protocol that defines the layout of an internet address (IP Address).
Hierarchical. Scalable (easy to add more networks and more devices).
93.184.216.34
93 is network, 184 is subnetwork, 216 is sub sub network, and 34 is device.
According to the Domain Name System (DNS), which of the following is a subdomain of the domain example.com?
What is HTTP?
HyperText Transfer Protocol (HTTP) - defines how computers request and receive HyperText information
HyperText Markup Language (HTML)
TCP/IP, DNS, Routing, all work together to send packets over the internet. HTTP makes sure the information inside the packets can be understood.
What are the legal and ethical concerns that arise from the internet?
Access to copyrighted material, anonymity, censorship.
What is a network?
A group of two or more computer systems linked together.
IPv4 vs. IPv6
IPv4: 32 bits, 2^32
IPv6: 128 bits, 2^128
What is routing?
The process of sending data between two computers on the internet. The data is sent through routers that determine the route. It is also redundant.
1. The URL
2. Create an HTTP request
3. Use DNS to get the IP Address
4. TCP/IP breaks the request into packets
5. Packets are routed to the proper IP Address
6. The original request is pieced together from the packets
7. The server creates an HTTP response
8. TCP breaks up the response into packets
9. The response packets are routed back to the computer
10. The original response is pieced together from the packets
11. The page is rendered!
Which of the following statements are true about the Internet?
I - The Internet connects devices and networks all over the world
II - The Internet helps people collaborate to solve problems
III - The Internet helps people communicate
IV - There are no negative consequences of the Internet, it is purely positive
I, II, III
How do we send digital information?
Electricity: Ethernet Cables (cheap, but only covers medium distances), low voltage/high voltage
Light: Fiber Optic Cables (long distance, expensive), bright light/dim light
Radio: WiFi Router, Cell Tower (wireless, short distance), high frequency/low frequency
What are the steps for rendering a web page?
1. The URL (Uniform Resource Locator - www.example.com/homepage.html, www.example.com is the domain (where in the internet you are looking for the resource), homepage.html is the path (what resource you are requesting). You type the URL into your browser.
2. The Request (the browser sends a message to a server requesting resource).
3. The Response (the server sends a response to the browser with the resource attached).
4. Rendering the Page (your browser takes the resource and renders it in the browser window).
Messages will be sent to the router with the lowest cost. What is the cost?
How close is the IP Address? Is the router trustworthy? Is the connection fast?
What is parallel and distributed computing?
SEQUENTIAL: Completes one task at a time, in order. SLOWER. Easier to find bugs. No setup needed.
PARALLEL/DISTRIBUTED: Completes multiple tasks at a time, simultaneously. Usually FASTER. Difficult to find bugs. Difficult to use/expensive and setup correctly. Scalable, reliable, fault tolerant.