> For the complete documentation index, see [llms.txt](https://prosbcdocs.telcobridges.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://prosbcdocs.telcobridges.com/telecom-references/protocols/link-alarms.md).

# Link Alarms

The link alarm (event) notification message is received by the host application when a MTP3 link is reporting an error.

General explanation of the field of event notification link alarm:

* The **Link handle** field specifies the handle of the MTP3 link instance

***

* The **Alarm** field indicates an alarm that can be reported at the link level. The following values are allowed:

| Link Alarm             | Description                                                          |
| ---------------------- | -------------------------------------------------------------------- |
| Up                     | Link activated or restored                                           |
| Down                   | Link deactivated or failed                                           |
| MTP2 not available     | MTP2 link has been removed                                           |
| Inhibited locally      | Link inhibited locally (management initiated)                        |
| Inhibited remotely     | Link inhibited remotely (remote node initiated action)               |
| Uninhibited locally    | Link uninhibited locally (Manager ctrl request)                      |
| Uninhibited remotely   | Link uninhibited by remote end                                       |
| Inhibited denied       | Link inhibit request from management denied                          |
| Uninhibited denied     | Link uninhibit request from management denied                        |
| Blocked locally        | Link locally blocked (Manager ctrl request)                          |
| Blocked remotely       | Link remotely blocked (unknown cause)                                |
| Unblocked locally      | Link unblocked (Manager ctrl request)                                |
| Unblocked remotely     | Link unblocked by remote end (unknown cause)                         |
| Congested              | Local link congested                                                 |
| Congestion stopped     | Local link congestion abated                                         |
| Emergency              | Link is in emergency state                                           |
| Emergency stopped      | Link is no more in emergency state                                   |
| Invalid SLC remote end | A signaling link test message (SLT/SLA) received with an invalid SLC |
| Invalid OPC remote end | A signaling link test message (SLT/SLA) received with an invalid OPC |
| SDT data drop          | Data dropped; the cause will also be set                             |

***

* The **Cause** field specifies the alarm cause according to alarm type. The following values are allowed:

| Link Alarm Cause                  | Description                                |
| --------------------------------- | ------------------------------------------ |
| Decode error                      | Decode error                               |
| Invalid message length            | Invalid message length                     |
| Link is inactive                  | Link is inactive                           |
| Timer T17 expired                 | Timer T17 expired                          |
| Invalid OPC                       | Invalid OPC                                |
| Remote negatively acknowledged    | Remote end negatively acknowledged         |
| Unknown                           | Unknown cause                              |
| Invalid test pattern              | Invalid test pattern in SRT/SRA            |
| Uninhibition in progress          | Uninhibition in progress                   |
| No remote acknowledgment          | No acknowledgment received from remote end |
| Path unavailable                  | Route to the point code not available      |
| Restoration failed                | Link restoration failed                    |
| T32 expired                       | Timer T32 (SLT Timer) expired              |
| Remote initiation                 | Remote node initiated action               |
| Management initiation             | Layer manager initiated action             |
| Local route management initiation | Route management initiated action          |
| Self-restart                      | Action due to self-restart                 |
| Adjacent restart                  | Action due to adjacent restart             |
| NIF OPC                           | --                                         |
| Invalid DPC                       | Invalid DPC                                |
| Inhibition in progress            | Inhibition in progress                     |
| MTP2 layer disconnected           | MTP2 layer disconnected                    |
| Linkset deactivated               | Linkset deactivated                        |
| DPC unavailable                   | DPC unavailable                            |
| Slave synchronization             | Slave synchronization                      |


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://prosbcdocs.telcobridges.com/telecom-references/protocols/link-alarms.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.