> 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/ss7-and-signalling/mtp3/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                      |


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