AP Computer Science Principles - Computer Networks & The Internet

packet

A small piece of data transmitted over a packet-switching network. The TCP/IP suite governs the transmission of data packets over a network, from one device to another.

Network

a group of two or more computer systems linked together

World Wide Web

An Internet application that is based on the HTTP protocol.

Client

A computer or software application that requests services from a server located on the internet- e.g. a Web browser is an example of a client.

SMTP/POP

Simple Mail Transfer Protocol (SMTP) and Post Office Protocol (POP) are sets of rules that govern the email services.

URI

Uniform Resource Identifier (URI) is WWW identier that uniquely identifies a resource on the WWW -- e.g., http://host.com'.

protocol

A set of rules governing the exchange or transmission of data between devices.

Modem

Modulator-Demodulator: A modem is the device that allows devices to connect to the internet. It does this by converting digital signals from these devices into analog signals. Modems also do the opposite by converting incoming analog signals into digital signals so that they can be processed by your device.

Digital Divide

the gap between those with Internet access and those without it. But the digital divide is multifaceted and includes many factors such as access, affordability, quality, and relevance.

Ethernet

A type of network that uses wires to connect computers. Ethernet protocol is a set of rules that governs how data is transmitted between devices on a wired network.

Host

An internet host computer, or server, is a computer that's connected directly to the internet- often a computer that provides certain services or resources

Bandwidth

the rate at which data is downloaded or uploaded in a network. Measured in bits per second (bps)

LAN

A local area network connects computer devices within a school, office, or home. LANs are limited to a small geographic area, usually within a 1 mile radius.

WAN

(Wide Area Network) A network that connects computers and other resources over great distances. WANs can be very large covering hundreds, sometimes thousands, of miles.

Server

A server is a host that provides some kind of online service- e.g Google's Gmail service

HTTP

The hypertext transfer protocol is the set of rules that governs the WWW application. HTTP works as a request-response protocol between a client and server.

HTML

HyperText Markup Language, the authoring language used to create documents on the World Wide Web.

Router

A router is a networking device that forwards data packets between computer networks.

ISP

An Internet service provider (ISP) is an organization that provides services for accessing, using, or participating in the Internet. ISPs typically advertise their download speeds to consumers.

WiFi

Wireless Fidelity. A Wifi network uses radio waves to connect devices (computers, smart phones, printers). Wifi range is around 150ft indoors. Obstructions, like walls and floors, will reduce the range.

Latency

a measure of the time it takes for a piece of data to reach its destination. Measured in milliseconds (ms)

Ping

ping is a network test that measures the time it takes for a tiny data packet to leave your device, travel to a server and for a response to come back. Measured in milliseconds (ms)

HTTPS

Hypertext Transfer Protocol Secure: a protocol for secure (trusted, encrypted) communication over the Internet.

SSL

Secure Sockets Layer: a protocol for establishing an encrypted link between a web server and a browser.

Star Network

All computer devices are connected directly to a central hub or switch. This is fault tolerant because if one computer fails, it does not affect the other devices. Although, if the central hub/switch fails, then all connected devices fail.

The Internet

Capital "I" The Internet is the global public network of independent & autonomous networks that are governed by the Internet Protocol (IP) suite. It is a fault tolerant mesh network.

Ring Network

Each device is connected to each other in a closed loop. Each data packed is passed around the loop until it reaches the final destination. This topology is easy to install/troubleshoot but it is old and if one computer goes down, or if one cable connection is broken, data flow would be disrupted.

Mesh Network

Each device on the network is connected to every other computer on the network. Mesh networks have high redundancy and are very fault tolerant. Can be expensive due to the amount of equipment and cabling required for setup.

Bus Network

A network topology where each device is connected to a single cable or backbone via T-connectors. Easy and inexpensive to setup but if there is an opening anywhere in the network the network could fail and data could be lost.

Bluetooth

Bluetooth uses ultra-high frequency (UHF) radio waves to transmit data between devices. it is the standard for the short-range wireless interconnection of mobile phones, computers, and other electronic devices.

Cryptography

secret writing; the science of encoding and decoding messages

Encryption

Turning plaintext into cyphertext. The process of encoding messages to keep them secret, so only "authorized" parties can read it.

Decryption

The process of converting a ciphertext back into plaintext. Requires a key and an algorithm.

Caesar Cipher

Algorithm that shifts the alphabet by N number of letters to create a cipher alphabet. For example, a cipher alphabet with a sift of +3 would start with the letter D.

Enigma

During World War II, the Germans used the Enigma, a cipher machine, to develop nearly unbreakable codes for sending secret messages. The Allies were eventually able to crack Enigma and gain access to German intelligence.

TCP/IP

Transmission Control Protocol/Internet Protocol. The set of rules that govern how computers communicate over networks. It's the standard for how data is exchanged on the internet.