| Label | Definition | Layer | Description |
|---|---|---|---|
| AIS | Alarm Indication Signal | MS, PATH | |
| FEBE | Far End Block Error | see REI | |
| FERF | Far End Receive Failure | see RDI | |
| ISF | Incoming Signal Failure - bejövő jel hiba | ||
| LOP | Loss of Pointer - nincs pointer | ||
| PLM | Payload Mishmatch | ||
| RDI | Remote Defect Indication (former FERF) | ||
| REI | Remote Error Indication (former FEBE) | ||
| RFI | Remote Failure Indication | ||
| SLM | Signal Label Mishmatch | ||
| TIM | Trace Identifier Mishmatch |