Amendment 1 to Recommendation ITU-T G.8013/Y.1731 (2011) provides the following modifications:

The proactive loss measurement messages/loss measurement reply (LMM/LMR).

Updates on performance monitoring (PM) and client signal fail (CSF) related description.

Update of references and abbreviations.

New clause 8.4.2 on dual-ended ETH-SLM.

New clause 9.24 on 1SL PDU.

New clause 10.24 on 1SL (One-way synthetic loss measurement).