MLR2 Frontend
MLR2 Frontend
The MLR2 Frontend sends SBN's signals on to an external alarm receiving centre (ARC) using the MLR2 protocol. It lets SBN Media appear to the ARC as a SurGard-style receiver, forwarding each alarm as it is raised.
Overview
Most SBN Media services receive alarms; the MLR2 Frontend does the opposite - it forwards them out. As signals are raised for a tenant, it drains them and delivers each one to an ARC over a TCP link, formatted as MLR2 (SurGard/SIA) so the ARC's automation software handles it like any other receiver line.
Each output link is a line. You define a line whose address is mlr2:<host>:<port> - the host and port the MLR2 Frontend binds and connects from - set its dealer to the tenant whose signals it should forward, and add the rules that map each signal to a SurGard receiver and line number. The link is kept alive with a periodic heartbeat, and it can stamp its own supervisory frames so the ARC can tell the link is healthy.
- Runs: When configured; at most one per host. Needed when SBN signals must be forwarded to an ARC over MLR2.
- Required: Only if you forward signals to an MLR2 / SurGard receiving centre. Not needed otherwise.
- Depends on: NATS, and the line configuration (which defines each ARC link and its mapping rules).
Configuration
The MLR2 Frontend has no settings of its own - it is configured entirely through the line configuration. Each output link is a line keyed by mlr2:<host>:<port>, and the line's dealer is the tenant whose signals that link forwards.
These settings go on each MLR2 line:
Setting | Description |
|---|---|
| The SBN tenant whose signals this link forwards. Required. |
| Set to |
| The rules that map a signal to a SurGard receiver and line number (see below). |
| The receiver and line number stamped on the link's own supervisory (link-alive) frames. Defaults to |
| How often to send the link heartbeat, in seconds. Defaults to the protocol's standard cadence (30 seconds). Set per link so each ARC can have its own keepalive rate. |
| Optional. For a two-way-voice alarm, the extension, |
After changing the configuration in sbn-media.local.yaml, apply it with ./sbn-media config reload - new and changed links are picked up without restarting the service.
Mapping signals to receiver and line numbers
receiverLines is an ordered list of rules. Each rule has a when (which signals it matches) and a then (the SurGard receiver and line number to stamp, for example 01006 - receiver 01, line 006). The most specific match wins; a rule with an empty when acts as the default. If no rule matches, 000 is used.
A when can match on:
protocol- the signal's source protocol (for examplep100orvoip), matched exactly.callerId- matched by prefix; a single trailing*is a wildcard.account- matched by prefix; a single trailing*is a wildcard.
Security
The MLR2 Frontend honours the built-in SBN Media firewall, so you can restrict which hosts it accepts connections from with the firewall configuration in addition to your network firewall. Because the link carries live alarm traffic, keep it on a trusted network or a VPN to the ARC.
FAQ
How do I add a link to an ARC?
Add a line to the line configuration keyed mlr2:<host>:<port>, set its dealer to the tenant whose signals it should forward, and add the receiverLines rules that map signals to the ARC's receiver and line numbers. Reload the configuration to apply it.
How does a signal get its receiver and line number?
From the receiverLines rules on the link. They are tried in order, the most specific match wins, and a rule with no when is the default. If nothing matches, 000 is used.
Can one host forward more than one tenant, or feed more than one ARC?
Yes. Add one line per link - each with its own dealer and port - and the single MLR2 Frontend on the host runs them all.
The ARC says the link keeps dropping.
Check the heartbeat: set heartbeatIntervalSec to the cadence the ARC expects (some expect 30 seconds, others differ), and confirm the network path and any firewall between the host and the ARC stays open.
Related pages
- SBN Media Overview (
SBN-Media/overview) - Installing and Configuring SBN Media (
SBN-Media/installation) - Line Configuration (
SBN-Media/Configuration/line-configuration) - Alarm Protocols (
SBN-Media/Configuration/protocols) - Firewall (
SBN-Media/Configuration/firewall) - SBN Frontend (
SBN-Media/Platform/sbn-frontend)