Glossary
Review the definitions for terms used across Cloudflare’s Magic Transit documentation.
| Term | Definition |
| anycast | Anycast is a network addressing and routing method in which incoming requests can be routed to a variety of different locations. Anycast typically routes incoming traffic to the nearest data center with the capacity to process the request efficiently. |
| data packet | A data packet is a unit of data consisting of user and control information. Information in a network is broken down into packets, that might follow different paths to their final destination. |
| equal-cost multi-path routing | A technique that uses hashes calculated from packet data to determine the route chosen. |
| GRE tunnel | Stands for generic routing encapsulation. It is a protocol wrapping one data packet within another type of data packet. This is useful for enabling protocols that are not normally supported by a network. |
| ICMP | Internet Control Message Protocol (ICMP) is used by network devices to send error messages and other operational information. ICMP is useful for diagnostic purposes, for example. |
| Internet key exchange (IKE) | The protocol Cloudflare uses to create the IPsec tunnel between Magic WAN and the customer’s device. |
| IPsec tunnel | Stands for Internet Protocol secure. It is a group of protocols for securing connections between devices, by encrypting IP packets. |
| letter of agency | Sometimes referred to as a Letter of Authorization. A document that authorizes Cloudflare to advertise your prefixes. This is required so transit providers can accept the routes Cloudflare advertises on your behalf. |
| maximum segment size (MSS) | MSS limits the size of packets, or small chunks of data, that travel across a network, such as the Internet. |
| on-ramp | Refers to a way of connecting a business network to Cloudflare. Examples of on-ramps, or ways to connect to Cloudflare, are Anycast GRE tunnels, Anycast IPsec tunnels, Cloudflare Network Interconnect (CNI), Cloudflare Tunnel, and WARP. |
| policy-based routing | Policy-based routing (PBR) is a technique used to make routing decisions based on policies set by your administrador. |
| prefix | A number that identifies the network portion of an IP address. It tells devices if an IP address is on the same network or not. It is shown as a number after a slash (for example, Using an analogy, the prefix is like a street address. If an IP is in the same street, it belongs to the same network of devices. |
| static route | A fixed configuration to route traffic through Anycast tunnels from Cloudflare global network to the customer’s locations. |
| subnet | Also known as subnetwork. It refers to a network that is part of another network. |
| traffic steering | Cloudflare evaluates your route’s health and steers traffic according to priorities defined by you and / or tunnel health. |
| tunnel health-check | A probe sent by Cloudflare to check for tunnel health. If a tunnel is not considered healthy, Cloudflare reroutes traffic to one that is considered healthy. |