AP CSP Big Idea 4 Notes: Internet Architecture, Reliability, and Computing at Scale

Internet

A global system of interconnected networks that allows devices to communicate using shared protocols.

Protocol

An agreed-upon set of rules for how data is formatted, addressed, sent, and received so different systems can communicate.

World Wide Web (Web)

An application/service that runs on top of the Internet, using technologies like URLs, HTTP/HTTPS, and HTML to load webpages.

Network

A group of computing devices connected so they can send data to one another.

Router

A device that forwards data between networks by making decisions based on destination addressing information.

Packet

A small chunk of a larger message sent across a network, containing data and header information used for delivery.

Packet Switching

A communication method where messages are split into packets that travel independently and can be routed along different paths.

Metadata (Packet Headers)

Information attached to packets (such as destination address) that helps the network deliver and manage the data.

IP Address

A numeric identifier for a device (or interface) on an IP network, used to deliver packets to the correct destination.

Domain Name

A human-friendly name (e.g., example.com) that corresponds to an IP address.

Domain Name System (DNS)

A distributed system that translates domain names into IP addresses; it does not route packets.

Routing

The process of choosing paths through networks so packets can move from source to destination.

Routing Table

A router’s stored information about where to send packets next to reach particular destinations.

Distributed Decision-Making (in Routing)

The idea that many routers make local forwarding decisions; no single computer has a complete, real-time map of the entire Internet.

Transmission Control Protocol (TCP)

A transport protocol that provides reliable, ordered delivery by handling missing or out-of-order packets (e.g., via retransmission).

User Datagram Protocol (UDP)

A transport protocol with less overhead that can be faster but does not guarantee reliable, ordered delivery.

HTTP/HTTPS

Web protocols used for communication between browsers and web servers; HTTPS is the encrypted (secure) version.

Bandwidth

How much data can be transmitted per unit time (network capacity).

Latency

The time it takes data to travel from sender to receiver (network delay).

Fault Tolerance

The ability of a system to keep operating correctly (or acceptably) even when some components fail.

Redundancy

Having multiple paths or duplicate components so a failure in one part doesn’t stop communication or service.

Single Point of Failure

A critical component with no backup; if it fails, the system or service can be severely disrupted.

Cascading Failure

A failure pattern where load shifts after an outage overloads remaining components, causing additional failures.

Parallel Computing

Using multiple processors/cores at the same time (often within one machine) to work on different parts of a single task.

Distributed Computing

Using multiple computers (nodes) over a network to cooperate on a task; adds network communication overhead but improves scalability and fault tolerance.