IB Computer Science Topic A2: Networks Key Definitions

The application layer provides the interface between applications and the network.

Asymmetric cryptography gives each party a mathematically linked key pair: a public key that can be published to anyone and a private key that never leaves its owner. It solves key distribution but is far slower than symmetric cryptography.

Attenuation is the loss of signal strength as a signal travels through a transmission medium. It sets how far a link can run before the signal has to be regenerated by a repeater or a switch.

Bandwidth is the maximum amount of data a link can carry per second, usually measured in bits per second. On a shared medium such as wireless it is divided between all the devices using the same channel.

Cloud computing delivers processing power, storage and applications as an on demand service from a provider's data centre, so an organisation rents capacity over a network instead of buying and maintaining its own hardware.

A header a server sends to the browser that lists which sources the page is allowed to load code from, which is what blocks cross-site scripting (XSS).

Convergence is the period after a network change during which routers exchange updates until every routing table holds a consistent view of the network.

Cross-site scripting (XSS) is an attack in which a script is placed into content a website stores and serves, so it runs in the browser of every other user who views that content.

Deep packet inspection (DPI) is filtering that reads the data a packet carries as well as its header, so a firewall can act on the contents of a request rather than only on its addresses, ports and protocol.

A digital certificate is an electronic document that binds a public key to the identity of its owner. A certificate authority verifies that identity and signs the certificate, so a client can check the binding before trusting the key.

Distributed denial of service (DDoS) is an attack that makes a service unavailable by flooding it with traffic from many compromised devices at once, so legitimate requests cannot be served.

A distributed system is a set of independent computers, called nodes, that cooperate on a single task while appearing to the user as one system. Because the work and the data are replicated across nodes, the system keeps running when an individual node fails.

Dynamic Host Configuration Protocol (DHCP) automatically assigns IP addresses and network configuration settings to devices on a network.

Dynamic routing is a method in which routers run a routing protocol to discover routes and recalculate them automatically when the network changes.

Edge computing processes data on or beside the device that produced it, rather than sending it to a central data centre first. Removing that round trip is what allows a response in milliseconds.

Encryption converts readable plaintext into unreadable ciphertext using an algorithm and a key. The process is reversible: the right key turns the ciphertext back into the original plaintext.

Firewalls are security devices that monitor and control network traffic based on predetermined rules. They act as a barrier between trusted and untrusted networks.

Gateways are network devices that act as bridges between two networks using different protocols. They translate data formats and ensure seamless communication between disparate systems.

Hybrid networks combine elements from different topologies (e.g., star and mesh) to optimize performance, reliability, and scalability.

Hypertext Transfer Protocol (HTTP) is the foundational protocol for data communication on the World Wide Web.

The internet layer handles packetization, addressing, and routing.

An IP address is the numerical label given to a device on a network, carried as the source and destination fields in the header of every packet. Routers read the destination field to decide where to forward the packet next.

A LAN connects devices over a short distance, typically within a building or campus.

Malware is software written to damage a system, disrupt its operation, or gain unauthorised access to it, including ransomware, spyware, rootkits, trojans, worms and keyloggers.