Technical Glossary — Networking & Speed Test

A

ADSL (Asymmetric Digital Subscriber Line)

An internet connection technology that runs over a traditional telephone line. Typical speeds: 7–24 Mbps download, 1–3 Mbps upload. Still common in areas not covered by fibre optic.

API (Application Programming Interface)

An interface that enables communication between different pieces of software. Essential for integrating web services, automating processes and building interconnected applications. RESTful APIs are the modern standard for web services.

ARP (Address Resolution Protocol)

A protocol that maps IP addresses to physical MAC addresses on the local network. Fundamental for communication between devices on the same subnet.

Two-Factor Authentication (2FA)

A security system that requires two methods of identity verification: something you know (password) plus something you have (phone) or something you are (biometrics).

B

Backup

A safety copy of data. Types: full (copies everything), incremental (only files changed since the last backup), differential (changes since the last full backup).

Bandwidth

The maximum data transmission capacity of a connection, expressed in Mbps or Gbps. It indicates how much data can pass per unit of time, independent of latency.

Bufferbloat

A phenomenon whereby excessively large buffers in routers cause very high latency under load, degrading interactive experiences (gaming, video calls) even on fast connections. Our test also measures latency under load to detect bufferbloat.

C

CDN (Content Delivery Network)

A geographically distributed network of servers that delivers web content from the edge node closest to the user, reducing latency and improving load times.

CGNAT (Carrier-Grade NAT)

A technique used by operators to share a single public IP address among many users. Can cause issues with peer-to-peer services and some applications that require inbound connections.

CNAME (Canonical Name)

A DNS record that maps one domain name to another name (alias). Used to point subdomains to third-party domains (e.g. CDN, cloud services).

D

DNS (Domain Name System)

The system that translates domain names (e.g. speedtest.it) into numeric IP addresses. It is the “phone book” of the internet. A slow DNS increases page load times even on a fast connection.

Download

The speed at which your device receives data from the internet, expressed in Mbps. It affects web browsing, video streaming and file downloads.

DHCP (Dynamic Host Configuration Protocol)

A protocol that automatically assigns IP addresses and other network parameters (gateway, DNS) to connected devices, avoiding manual configuration.

F

Fibre optic (FTTH/FTTC)

A connection technology that uses light to transmit data. FTTH (Fiber To The Home) brings fibre directly into the home: speeds up to 10 Gbps symmetric. FTTC (Fiber To The Cabinet) reaches the street cabinet and then uses copper: speeds up to 200–300 Mbps.

Firewall

A security system that monitors and filters network traffic based on predefined rules. Can be hardware (in routers) or software (in the operating system).

G

Gateway

A device (usually the router) that acts as an access point between the local network and the internet. It routes traffic between different networks.

H

Hash

A mathematical function that transforms variable-length data into a fixed-length string (e.g. SHA-256 always produces 64 hexadecimal characters). Used to verify file integrity and to store passwords securely.

HTTP/HTTPS

Protocols for transmitting web pages. HTTPS adds TLS/SSL encryption: data transmitted between browser and server cannot be read by third parties.

I

IP (Internet Protocol)

The fundamental internet protocol that assigns a unique address (IP address) to every connected device. There are two versions: IPv4 (32-bit, e.g. 192.168.1.1) and IPv6 (128-bit, e.g. 2001:db8::1).

ISP (Internet Service Provider)

An operator that provides internet access (e.g. BT, Virgin Media, Sky, Vodafone, AT&T, Comcast). Performance varies by technology, geographic area and network load.

J

Jitter

The variation in delay (latency) over time. High jitter causes instability in video calls and online gaming, even with an acceptable average ping. It is measured in milliseconds.

L

Latency

The time a data packet takes to travel from your device to the server and back (round-trip time). Measured in milliseconds (ms). Values below 20 ms are excellent; above 100 ms the interactive experience degrades.

M

MAC Address

A unique identifier assigned to the network interface of each device during manufacturing. Used for addressing on the local network (OSI layer 2).

Mbps (Megabits per second)

The unit of measurement for connection speed. 1 Mbps = 1,000,000 bits per second. Note: 1 byte = 8 bits, so 100 Mbps corresponds to ~12.5 MB/s of effective download throughput.

N

NAT (Network Address Translation)

A technique that allows multiple devices on a local network to share a single public IP address. The router keeps track of connections and forwards responses to the correct device.

ndt7

A speed measurement protocol developed by Measurement Lab (M-Lab). It uses WebSockets over HTTPS and also measures latency under load (bufferbloat). It is one of the engines supported by our speedtest.

P

Packet Loss

The percentage of data packets that do not reach their destination. Even 1% packet loss can cause significant problems in video calls and online gaming.

Ping

A command that measures response time (latency) to a network host by sending ICMP packets. The value in milliseconds indicates how “fast” the server responds. See also: latency, jitter.

PTR (Pointer Record)

A DNS record for reverse resolution: from IP address to domain name. Used to verify the identity of mail servers and in traceroutes.

Q

QoS (Quality of Service)

A mechanism that prioritises certain types of network traffic (e.g. video calls, VoIP) over others (background downloads). Implemented in routers to improve the experience on shared networks.

R

Router

A device that routes traffic between the local network and the internet. It assigns local IP addresses via DHCP, manages NAT and implements the basic firewall.

S

SSL/TLS

Cryptographic protocols that protect communications over the internet. TLS is the successor to SSL (now deprecated). A valid TLS certificate is indicated by the padlock in the browser and HTTPS in the URL.

Subnet

A logical division of an IP network into smaller segments. The subnet mask (e.g. /24 = 255.255.255.0) determines how many devices can belong to the same local network.

T

TCP (Transmission Control Protocol)

A transport protocol that guarantees ordered, error-free delivery of data. Used for the web, email and file downloads. Unlike UDP, it automatically handles retransmission of lost packets.

Traceroute

A diagnostic tool that shows the path packets take from your connection to the destination server, hop by hop, with the latency of each hop. Useful for identifying where bottlenecks occur.

U

UDP (User Datagram Protocol)

A connectionless transport protocol, faster than TCP but without delivery guarantees. Used for streaming, online gaming, DNS and VoIP: contexts where speed is more important than reliability.

Upload

The speed at which your device sends data to the internet, expressed in Mbps. Important for video calls, live streaming, cloud backups and file transfers.

V

VPN (Virtual Private Network)

An encrypted tunnel that protects internet traffic and hides the real IP address. Used for privacy, security on public networks and access to geo-restricted content. Can reduce connection speed.

W

WHOIS

A protocol and service for obtaining information about a domain or IP address: registrar, registration and expiry dates, nameservers, registrant data (when public).

WireGuard

A modern, lightweight VPN protocol (approximately 4,000 lines of code vs 400,000 for OpenVPN). Offers superior performance, modern cryptography (ChaCha20, Curve25519) and simpler configuration.