ITU-T G.8275.1 (PTP Profile - FTS) One-Page Summary
Title: PTP telecom profile for phase/time synchronization with full timing support from the network
Summary
Defines the profile (options, parameters, extensions) for the use of PTP for packet-based time/phase delivery over a network of boundary or transparent clocks
Main use-case is time synchronization of TDD-based cellular basestations
Status
Current version: 4.2 Edition, August 2024, Amendment 2 to 2022 Revision
Download from: http://www.itu.int/ITU-T/recommendations/rec.aspx?rec=12815
Key Contents
Profile Features:
Operates directly over Ethernet using multicast messaging
Message rate 16 messages per second
Requires a BC or TC at every node in the network, with physical layer frequency support (e.g. SyncE)
Planned protection schemes in accordance with existing telecom practice
Alternate BMCA, modified from the default to allow multiple active GMs for redundancy
Clock Class Assignment:
Phase/Time Traceability Description | defaultDS.clockClass | Input SyncE QL | Frequency Traceable Flag | Time Traceable Flag |
|---|---|---|---|---|
T-GM connected to a PRTC in locked mode (e.g. PRTC traceable to GNSS) | 6 | n/a | TRUE | TRUE |
T-GM in holdover, within holdover specification | 7 | PRC / PRS | TRUE | TRUE |
Non-PRC | FALSE | TRUE | ||
T-BC in holdover, within holdover specification | 135 | PRC / PRS | TRUE | TRUE |
Non-PRC | FALSE | TRUE | ||
T-GM in holdover, out of holdover specification | 140 | PRC / PRS | TRUE | FALSE |
150 | SSU-A / Stratum 2 | FALSE | FALSE | |
160 | SSU-B / Stratum 3E | FALSE | FALSE | |
T-BC in holdover, out of holdover specification | 165 | n/a | Depends on QL of input SyncE if available | FALSE |
T-GM or T-BC without time reference since start-up | 248 | n/a | ||
Slave only OC (does not send Announce messages) | 255 | n/a |