Unit 4: How the Internet Works
Lab 1: Computer Networks
The Internet is a computer network that uses open protocols to standardize communication. A computing device connected to an Internet-connected device is required to access the Internet.
- A computer network is an interconnected computing system that is capable of sending or receiving data.
- A computing system is a group of computing devices and programs working together for a common purpose.
- A computing device is a physical object that can run a program, such as computers, tablets, cell phones, and smart sensors.
- The World Wide Web is a system of linked pages, programs, and files that uses the Internet.
- A router is a computer that passes information from one network to another.
Your computer probably uses a router that is somewhere in your home to connect to your ISP.
- ISPs (Internet Service Providers) are the companies who sell Internet access to homes and institutions.
The computers connected to the Internet and the connections among them don't belong to any one organization. Different ISPs provide the Internet to different communities. And typically within a large organization (such as a university), the Internet connections are provided by the organization itself.
- Bandwidth is the maximum amount of data that can be sent in a fixed amount of time (for digital data, it is measured in bits per second). Higher bandwidth is better because the data will travel more quickly.
- Storing data in the cloud means storing it somewhere on the Internet, but you don't know where. The cloud service provider (Google, Dropbox, Amazon, Snap!, etc.) manages the actual storage location.
CSN-1.A.5, CSN-1.A.6, CSN-1.B.6, CSN-1.E.2, CSN-1.E.5
- A path is a sequence of directly connected computing devices that connect a sender to a receiver.
- Routing is the process of finding a path from sender to receiver.
- Scalability is the ability of the Internet to keep working as it grows.
- Redundancy is the inclusion of back-up elements in case one part fails.
- Fault tolerance is the ability of a system to work around problems.
- A protocol is set of rules that specify the behavior of a system.
- An IP address is a unique number assigned to each device on a computer network.
- A packet is a small chunk of any kind of data (text, numbers, lists, etc.) and metadata (information about the data) that is passed through the Internet as a data stream.
- Packet switching means that the Internet sends short bursts of information, not long continuous strings.
TCP/IP is a pair of protocols that provide two levels of abstraction:
- IP (Internet Protocol) lets your computer pretend it has a direct connection to another computer. The routers at every connection point on the Internet run IP, which transmits packets from one IP address to another.
- TCP (Transmission Control Protocol) lets your computer pretend it has a reliable connection to the other computer. The computers (including servers) at the two endpoints of a communication run TCP, which guarantees that packets arrive successfully.
Lab 2: Cybersecurity
: Encryption and Decryption
- Encryption is the process of encoding data to prevent unauthorized access.
- Decryption is the process of decoding the data.
: Symmetric Encryption
Substitution ciphers are examples of symmetric encryption because they use the same key for both encryption and decryption.
Public key encryption uses a pair of keys: a public key for encryption and a private key for decryption. The sender uses the public key to encrypt the message, and receiver uses their private key to decrypt it.
SSL/TLS (secure sockets layer/transport layer security) is the standard used for cryptographically secured information transfer on the Internet.
Certificate authorities are organizations that issue digital certificates to verify who owns the encryption keys used for secured communications.
Instead of trusting that the website is who they say they are, you now have to trust that the Certificate Authority is reliable.
- Malware is software that was designed to harm or take partial control over your computer.
- Keylogging software is a kind of malware that records every key pressed by a user.
- A computer virus is a type of malware that spreads and infects other computers. Viruses can attach themselves to legitimate programs.
- Antivirus or anti-malware software is software designed to scan your files and Internet transmissions looking for malware.
- A firewall is a security system that controls the kinds of connections that can be made between a computer or network and the outside world.
- Phishing is a common security attack in which the victim is tricked into giving up personal information or downloading malware.
A DDoS (Distributed Denial of Service) attack uses a virus to flood a server with many requests from many computers at once so that users of that server are denied service.
A rogue access point
is a wireless access point that gives access to a secure network without the authorization of the network administrator.
Lab 3: Community and Online Interactions
The digital divide refers to unequal access to computers and the Internet based on poverty, racism, sexism, isolation in the countryside, age, and other factors. The digital divide affects both individuals within a country and countries themselves.
- Citizen science is scientific research conducted in whole or part by distributed individuals, many of whom may not be scientists, who contribute relevant data to research using their own computing devices.
- Crowdsourcing is the general term for using the Internet to get a lot of people to help solve a problem. (Citizen science is a type of crowdsourcing.)
- A computing innovation can be physical (such as a self-driving car), non-physical software (such as picture editing software), or conceptual (such as the idea of e-commerce), but regardless of the form, they must include a program as an integral part of their function.
Lab 4: Data Representation and Compression
A bit is a single unit of data that can only have one of two values. We usually represent the two values as 0 (off) and 1 (on).
A byte is eight bits.
A word is a sequence of however many bits the CPU processes at a time. As of 2017, words are 32 or 64 bits.
A binary sequence (also called a bitstream) is a string of ones and zeros.
Analog data have values that change smoothly, unlike digital data which change in discrete intervals.
Sampling means measuring values, called samples, of an analog signal at regular intervals.
The sampling rate is the number of samples measured per second.
width: the number of bits that a CPU processes at a time
word: a binary sequence of that many bits
Scientific notation (such as 2,350,000 = 2.35 × 106) uses powers of ten to represent very large or very small values. Floating point is the same idea but with powers of two.
The word "bit" is an abbreviation for binary digit.
: Lossless Compression
Lossless data compression algorithms (such as PNG) are reversible (there is no loss in quality); you can reconstruct the original data.
: Lossy Compression
Lossy data compression algorithms are not fully reversible; you can reconstruct only an approximation of the original data.