Firewalls Glossary

DigitalOcean Cloud Firewalls are a network-based, stateful firewall service for Droplets provided at no additional cost. Cloud firewalls block all traffic that isn’t expressly permitted by a rule.

This glossary defines the core concepts behind firewalls to help build your mental model of how firewalls work and understand what the documentation is referring to when it uses certain terminology.

Classless Inter-Domain Routing notation, or CIDR notation, is a method of representing an IP address network range.
Internet Control Message Protocol (ICMP) is a network layer protocol used to diagnose problems between devices within a network.
A port is a communication endpoint of a network connection. A port is identified using a port number for each transport protocol.
A protocol is a set of rules a client and server adhere to when exchanging data through the internet.
SSH (Secure Shell Protocol) is a method to secure remote logins and communications from one computer to another which provides strong authentication and protects communication through strong encryption.
Tags are keywords associated with resources which help with managing resource ownership and organize lookups and actions on resources.
The Transmission Control Protocol (TCP) is a communication standard for programs and computing devices to exchange messages over a network.
User Datagram Protocol, or UDP, is an established low-latency connection communication protocol between applications.