A number of the relevant standards are the same as for ±1.5µs:

• ITU-T G.8271 (General) One-Page Summary
• ITU-T G.8271.1 (Network Limits - FTS) One-Page Summary
• ITU-T G.8261 (SyncE Network Limits) One-Page Summary
• ITU-T G.8272 (PRTC) One-Page Summary
• ITU-T G.8273 (Test Framework) One-Page Summary
• ITU-T G.8273.2 (T-BC and T-TSC) One-Page Summary
• ITU-T G.8275 (Architecture) One-Page Summary
• ITU-T G.8275.1 (PTP Profile - FTS) One-Page Summary

For enhanced clocks: