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Understanding the PTP G.8275.2 Enhanced Profile (Telecom Profile)

The Precision Time Protocol (PTP) G.8275.2 enhanced profile supports telecom applications that require accurate phase and time synchronization for phase alignment and time of day synchronization over a wide area network. This profile supports partial timing support (PTS) using PTP over IPv4 unicast, ordinary and boundary clocks, and unicast negotiation.

With the G.8275.2 enhanced profile, you can use either boundary or ordinary clocks. Up to 512 downstream client clocks are supported. Member clock ports can recover clocks from one-step or two-step primary clocks, but primary clocks only support one-step PTP.

The G.8275.2 enhanced profile includes the following functionality:

  • Support for both ordinary clocks and boundary clocks.

  • Support for primary-only and client-only ports.

  • Support for node types T-BC-P (BC) and T-TSC-P (OC/BC).

  • Support for the alternate best primary clock algorithm.

  • Support for PTP with or without VLAN encapsulation and for two-way transfer. Unicast PTP over IPv4 transport is required.

  • Unicast negotiation with single and multiple TLVs support on the primary port. The primary accepts single and multiple TLV messages from the remote client for request, cancel, and ack messages. The primary responds with single or multiple TLV messages as appropriate. The “rate” TLV is ignored.

  • Reception and transmission of unicast Announce and Sync PTP packets.

  • Support for full domain and packet-rate ranges.

  • Support for manual mode, rather than unicast negotiation.

  • Support for aggregated Ethernet interfaces.

    You can configure an aggregated Ethernet interface and its configured IP address for PTP streams acting as slaves or primaries. IP hashing determines which physical link to use for the PTP traffic flows. Both IPv4 unicast and IPv6 unicast transport are supported.

  • Support for loopback interface.

    You can configure a loopback interface (there is only one loopback interface, and it is lo0.0) and its corresponding IP addresses for PTP streams acting as slaves or primaries. The IP address configured on lo0.0 is used as the local IP address in the PTP configuration statements, and the remote primary or client IP address is used to identify the destination forwarding direction. You can configure multiple IP addresses on lo0.0, which allows different unique PTP streams to co-exist on lo0.0. Although, the loopback interface is the same for both primaries and slaves, the IP addresses must be unique. Both IPv4 unicast and IPv6 unicast transport are supported.

With the G.8275.2 enhanced profile enabled, the following parameters can apply:

  • Priority1

    The allowed (and default) value is 128. (Not user-configurable.)

  • Priority2

    The range is from 0 to 255, and the default value is 128.

  • Domain number

    The range is from 44 to 63, and the default value is 44.

  • Clock mode

    The clock mode can be ordinary or boundary.

  • Duration of neighborhood rates

    The range is 60 to 1000 seconds, and the default value is 300 seconds.

  • clockAccuracy


  • offsetScaledLogVariance


  • slaveOnly

    The allowed values are True and False; the default value is False. (Not user-configurable; the value is set according to the setting of the clock mode: boundary or ordinary.)

  • localPriority

    The range is 1 to 255; the default value is 128.

  • Table 1: Announce, Sync, and Delay Request/ Response Rate Parameters


    Default Value

    Allowed Range of Values

    Announce rate

    • Primary: -3

    • Member: 0

    -3 – 0

    Delay request/response rate

    • Primary: -6

    • Member: -7

    -7 – -3

    Sync rate

    • Primary: -7

    • Member: -6

    -7 – -3