Software-defined tunnelling (SDT) - the overall management, control, and composition of dynamic virtual private networks and endpoints.
Duct - an active channel of a single standard protocol between two correlated endpoints. Ducts are stacked to be combined to form a tunnel. Both ends of a duct correlate, but don't need to be the same host for each connection.
Duct-point - one of two ends of a duct.
Service - the same as tunnel-segment or segment except this specifically refers to the configuration of a segment. "Segment configuration" it's a good term to use because it isn't user friendly. End users will see "service" in a configuration file on their machine.
Tunnel-segment or segment - A part of an active tunnel that was defined as a service on a single host. A collection of active duct-points and processes that implicitly coordinate with other nodes in a stratified way: a tunnel spans multiple hosts, and a tunnel-segment is one part of the tunnel that is confined to a single host. A tunnel-segment is composed of duct-points, while a conceptual tunnel is composed of conceptual ducts.
Tunnel - an operational network channel that securely forwards traffic bidirectionally. It runs as a composition segments of stacked duct points and processes, that work as stacked conceptual ducts across multiple hosts.
Duct type - the type of a duct or duct point, usually described in terms of a standard encapsulating protocol, like TCP, HTTP, TLS. Also may refer to non-encapsulating protocol, like Meet, and Operator.
Duct mode - the way two duct-points interact: encapsulating (ongoing), non-encapsulating (once off), or process (technically not a duct-point). Usually a duct mode is a description of the duct type. A Meet duct type is non-encapsulating.
Tunnel configuration - a conceptual configuration of the conceptual duct configurations over one or many nodes to create a tunnel.
Tunnel-segment activation - the initiation of a new tunnel-segment on a host.
Tunnel activation - the activation of a tunnel across one or more systems comprising of multiple tunnel-segments that are activating