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G.8275.2 Enhanced Profile

Thi topic talks about the G.8275.2 enhamced 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 and IPv6 unicast, ordinary and boundary clocks, and unicast negotiation with single and multiple TLVs support on the timeTransmitter port.

With the G.8275.2 enhanced profile, you can use either boundary or ordinary clocks. Up to 512 downstream timeReceiver clocks are supported. TimeReceiver clock ports can recover clocks from one-step or two-step timeTransmitter clocks, but timeTransmitter 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 timeTransmitter-only and timeReceiver-only ports.

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

  • Support for the alternate best timeTransmitter clock algorithm.

  • Support for PTP with or without VLAN encapsulation. Unicast PTP over IPv4 and IPv6 transport is supported.

  • Unicast negotiation with single and multiple TLVs support on the timeTransmitter port. The timeTransmitter accepts single and multiple TLV messages from the remote timeReceiver for request, cancel, and ack messages. The timeTransmitter 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 timeReceiver clocks or timeTransmitter clocks. IP hashing determines which physical link to use for the PTP traffic flows. Both IPv4 unicast and IPv6 unicast transport are supported.

    Note that the QFX5120-48T switch does not support G.8275.2.enh profile over aggregated Ethernet interfaces.

  • 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 timeReceiver clocks or timetransmitter clocks. The IP address configured on lo0.0 is used as the local IP address in the PTP configuration statements, and the remote timeTransmitter or timeReceiver 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 timeTransmitter clocks and timeReceiver clocks, the IP addresses must be unique. Both IPv4 unicast and IPv6 unicast transport are supported.

    Note that the QFX5120-48T switch does not support G.8275.2.enh profile over loopback interface.

  • Support for automatic or subnet-based timeReceiver clocks over the loopback interface. Any IPv4 or IPv6 PTP timeReceiver clock belonging to the subnet can join the timeTransmitter clock through unicast negotiation.

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 negotiated rates

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

  • clockAccuracy

    0xFE

  • offsetScaledLogVariance

    0xFFFF

  • 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

    Parameter

    Default Value

    Allowed Range of Values

    Announce rate

    0

    • TimeTransmitter: -3 to 4

    • TimeReceiver: -3 to 0

    Delay request/response rate

    -6

    • TimeReceiver: -7 to -3

    Sync rate

    -6

    • TimeTransmitter: -7 to 4

    • TimeReceiver: -7 to -3