# FreeDMR 2 Glossary

This glossary defines FreeDMR 2 terms. Legacy terms such as `SYSTEM`, `MASTER`, `BRIDGES`, and `#` reflector names describe current implementation details or compatibility views, not the primary FreeDMR 2 model.

**Access layer**: The part of FreeDMR that accepts client/repeater protocols such as HBP. It owns login, authentication, options, keepalive, access sessions, RF-facing slots, and RF-visible TG presentation.

**Access session**: A live connection-like relationship between FreeDMR and a client/repeater. It is identified by client DMR ID and transport/session metadata, not by a configured listener stanza.

**Listener**: A UDP socket/service endpoint that accepts one or more access sessions. A configured `MASTER` is a legacy listener-like concept, not the client identity.

**Client/repeater**: An HBP hotspot, repeater, gateway, bridge, or future access-side system connected to FreeDMR.

**Client DMR ID**: The DMR ID used by a client/repeater access session. Future routing should key primarily on client DMR ID, slot, and RF-visible TG.

**RF-visible TG**: The talkgroup number seen by the RF terminal or access-side device. In dial-a-TG this may be TG9 while the network conference TG is different.

**Conference TG**: The FreeDMR network talkgroup identity. Conceptually this is the conference bridge to which clients subscribe.

**Subscription**: Membership of a client slot/RF TG presentation in a conference TG.

**Static subscription**: A subscription created by configuration or policy and normally present for the session.

**Dial-a-TG subscription**: A subscription created by dial-a-TG control. It maps an RF-visible TG, traditionally TG9, to a selected conference TG.

**Default reflector**: A configured or client-requested default dial-a-TG style subscription for a session. Empty string, integer 0, or boolean false means no default reflector.

**Stream**: A voice call flow identified by stream metadata. AMBE voice is a stream; DMR data packets are packet-oriented and should not be treated as AMBE streams.

**Source server**: The server that originated or advertised the packet into the mesh, according to the FBP/OBP protocol version in use.

**Source repeater**: The access-side repeater/client identity carried when the protocol version supports it.

**Mesh peer**: Another FreeDMR/OpenBridge/FBP peer server connected through the mesh layer.

**Server ID**: A FreeDMR server identity. Server IDs are treated separately from client DMR IDs.

**Server sub-ID**: A subordinate server identity authorized under a server/sysop identity, for example backend or fault-tolerant deployments.

**Bridge-control message**: An out-of-band FBP/OBP control message, such as source quench or STUN.

**Packet plane**: The delay-sensitive path that receives, parses, routes, mutates where necessary, and sends DMR packets.

**Control plane**: Authenticated configuration, API, bridge-control, admission, and policy operations.

**Reporting plane**: Observational events and state export for dashboards, logs, lastheard, monitoring, and operators.

**Compatibility/export state**: A derived view that presents old FreeDMR/HBLink/dashboard shapes to consumers. It is not authoritative state.

**HBP**: Homebrew Protocol, used by many hotspots/repeaters on the access side.

**OBP**: OpenBridge Protocol version 1. It remains important as an open interop path where intentionally configured.

**FBP**: FreeDMR Bridge Protocol. Any OpenBridge-derived peer protocol version higher than 1 is termed FBP for FreeDMR clarity.

**DATA-GATEWAY**: A historical/early expression of a data-oriented FBP link. FreeDMR 2 should preserve data forwarding without making the core a GPS/SMS application processor.

**Source quench / BCSQ**: A bridge-control hint asking a peer to suppress a stream/TG toward us. It is optional and per stream/TG.

**STUN / BCST**: A broader bridge-control gate intended to stop all FBP traffic from a peer under the current conceptual model.

**OVCM**: Open Voice Channel Mode. ETSI service option bit 0x04 when explicitly used. HBLink legacy 0x20 is compatibility history, not standards-clean OVCM.

**Synthetic LC**: A generated Link Control value used when FreeDMR has to create fallback LC information.

**Real inbound LC**: LC decoded from received traffic. It should be preserved unchanged unless FreeDMR deliberately rewrites it.