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G.8275.1 Telecom Profile

G.8275.1 is a PTP profile for applications that require accurate phase and time synchronization. It supports the architecture defined in ITU-T G.8275 to enable the distribution of phase and time with full timing support and is based on the second version of PTP defined in IEEE 1588. You can configure the G.8275.1 profile by including the profile-type G.8275.1 statement at the [edit protocols ptp] hierarchy level.

Note:

  • If you don’t configure a profile, the device operates in IEEE1588v2 profile which is the default profile.

  • It is mandatory to configure Synchronous Ethernet (SyncE) and Hybrid mode when configuring the G.8275.1 profile.

The following sections give a brief overview about the types of clocks supported in the G.8275.1 profile and about the alternate Best TimeTransmitter Clock Algorithm (BTCA):

Types of Clocks Supported in the G.8275.1 Profile

There are two types of clocks supported in this profile—ordinary clock and the boundary clock.

There are two types of ordinary clocks:

  • One that can be only a grandmaster clock (Telecom grandmaster or T-GM)

  • One that can be only a timeReceiver clock (a timeReceiver-only ordinary clock or T-TSC)

There are two types of boundary clocks:

  • One that can be only a grandmaster clock (T-GM)

  • One that can become a timeTransmitter clock and a timeReceiver clock to another PTP clock (T-BC)

Alternate BTCA

The G.8275.1 profile uses an alternate Best TimeTransmitter Clock Algorithm (BTCA). The alternate BTCA allows:

  • A new per-port attribute named notSlave. The notSlave port attribute is implemented using the protocols ptp master stanza configuration.

  • Multiple active grandmaster clocks. If there are multiple active grandmasters, every clock that is not a grandmaster is synchronized by a single grandmaster in the PTP domain.

  • Per-port attribute local-priority to be used as a tie-breaker in the dataset comparison algorithm.

Hybrid Mode

Hybrid mode is the combined operation of Synchronous Ethernet (SyncE) and Precision Time Protocol (PTP). This approach leverages the strengths of both technologies to achieve accurate time synchronization across networks.

Synchronous Ethernet (SyncE) provides frequency synchronization at the physical layer, ensuring that all network nodes operate at the same frequency, whereas PTP synchronizes both frequency and phase (including time of day) over packet-switched networks. In hybrid mode, the frequency is derived from SyncE, while the phase and time of day are obtained from PTP. This combination improves synchronization accuracy and extends the number of network hops that can be supported, achieving clock synchronization accuracy in the order of tens of nanoseconds.

Enable hybrid mode while configuring the G.8275.1 telecom profile. To learn more about hybrid mode, see Hybrid Mode.