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Using PTP hardware

About PTP hardware

You can use the OpenShift Container Platform console or OpenShift CLI (oc) to install PTP by deploying the PTP Operator. The PTP Operator creates and manages the linuxptp services and provides the following features:

  • Discovery of the PTP-capable devices in the cluster.

  • Management of the configuration of linuxptp services.

  • Notification of PTP clock events that negatively affect the performance and reliability of your application with the PTP Operator cloud-event-proxy sidecar.

The PTP Operator works with PTP-capable devices on clusters provisioned only on bare-metal infrastructure.

About PTP

Precision Time Protocol (PTP) is used to synchronize clocks in a network. When used in conjunction with hardware support, PTP is capable of sub-microsecond accuracy, and is more accurate than Network Time Protocol (NTP).

The linuxptp package includes the ptp4l and phc2sys programs for clock synchronization. ptp4l implements the PTP boundary clock and ordinary clock. ptp4l synchronizes the PTP hardware clock to the source clock with hardware time stamping and synchronizes the system clock to the source clock with software time stamping. phc2sys is used for hardware time stamping to synchronize the system clock to the PTP hardware clock on the network interface controller (NIC).

Elements of a PTP domain

PTP is used to synchronize multiple nodes connected in a network, with clocks for each node. The clocks synchronized by PTP are organized in a source-destination hierarchy. The hierarchy is created and updated automatically by the best master clock (BMC) algorithm, which runs on every clock. Destination clocks are synchronized to source clocks, and destination clocks can themselves be the source for other downstream clocks. The following types of clocks can be included in configurations:

Grandmaster clock

The grandmaster clock provides standard time information to other clocks across the network and ensures accurate and stable synchronisation. It writes time stamps and responds to time requests from other clocks. Grandmaster clocks can be synchronized to a Global Positioning System (GPS) time source.

Ordinary clock

The ordinary clock has a single port connection that can play the role of source or destination clock, depending on its position in the network. The ordinary clock can read and write time stamps.

Boundary clock

The boundary clock has ports in two or more communication paths and can be a source and a destination to other destination clocks at the same time. The boundary clock works as a destination clock upstream. The destination clock receives the timing message, adjusts for delay, and then creates a new source time signal to pass down the network. The boundary clock produces a new timing packet that is still correctly synced with the source clock and can reduce the number of connected devices reporting directly to the source clock.

Advantages of PTP over NTP

One of the main advantages that PTP has over NTP is the hardware support present in various network interface controllers (NIC) and network switches. The specialized hardware allows PTP to account for delays in message transfer and improves the accuracy of time synchronization. To achieve the best possible accuracy, it is recommended that all networking components between PTP clocks are PTP hardware enabled.

Hardware-based PTP provides optimal accuracy, since the NIC can time stamp the PTP packets at the exact moment they are sent and received. Compare this to software-based PTP, which requires additional processing of the PTP packets by the operating system.

Before enabling PTP, ensure that NTP is disabled for the required nodes. You can disable the chrony time service (chronyd) using a MachineConfig custom resource. For more information, see Disabling chrony time service.

Using PTP with dual NIC hardware

OpenShift Container Platform supports single and dual NIC hardware for precision PTP timing in the cluster.

For 5G telco networks that deliver mid-band spectrum coverage, each virtual distributed unit (vDU) requires connections to 6 radio units (RUs). To make these connections, each vDU host requires 2 NICs configured as boundary clocks.

Dual NIC hardware allows you to connect each NIC to the same upstream leader clock with separate ptp4l instances for each NIC feeding the downstream clocks.

Installing the PTP Operator using the CLI

As a cluster administrator, you can install the Operator by using the CLI.

Prerequisites

  • A cluster installed on bare-metal hardware with nodes that have hardware that supports PTP.

  • Install the OpenShift CLI (oc).

  • Log in as a user with cluster-admin privileges.

Procedure

  1. Create a namespace for the PTP Operator.

    1. Save the following YAML in the ptp-namespace.yaml file:

      apiVersion: v1
kind: Namespace
metadata:
  name: openshift-ptp
  annotations:
    workload.openshift.io/allowed: management
  labels:
    name: openshift-ptp
    openshift.io/cluster-monitoring: "true"

    2. Create the Namespace CR:

      $ oc create -f ptp-namespace.yaml

  2. Create an Operator group for the PTP Operator.

    1. Save the following YAML in the ptp-operatorgroup.yaml file:

      apiVersion: operators.coreos.com/v1
kind: OperatorGroup
metadata:
  name: ptp-operators
  namespace: openshift-ptp
spec:
  targetNamespaces:
  - openshift-ptp

    2. Create the OperatorGroup CR:

      $ oc create -f ptp-operatorgroup.yaml

  3. Subscribe to the PTP Operator.

    1. Save the following YAML in the ptp-sub.yaml file:

      apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
  name: ptp-operator-subscription
  namespace: openshift-ptp
spec:
  channel: "stable"
  name: ptp-operator
  source: redhat-operators
  sourceNamespace: openshift-marketplace

    2. Create the Subscription CR:

      $ oc create -f ptp-sub.yaml

  4. To verify that the Operator is installed, enter the following command:

    $ oc get csv -n openshift-ptp -o custom-columns=Name:.metadata.name,Phase:.status.phase
    Example output
    Name                         Phase
4.12.0-202301261535          Succeeded

Installing the PTP Operator using the web console

As a cluster administrator, you can install the PTP Operator using the web console.

You have to create the namespace and operator group as mentioned in the previous section.
Procedure

  1. Install the PTP Operator using the OpenShift Container Platform web console:

    1. In the OpenShift Container Platform web console, click Operators → OperatorHub.

    2. Choose PTP Operator from the list of available Operators, and then click Install.

    3. On the Install Operator page, under A specific namespace on the cluster select openshift-ptp. Then, click Install.

  2. Optional: Verify that the PTP Operator installed successfully:

    1. Switch to the Operators → Installed Operators page.

    2. Ensure that PTP Operator is listed in the openshift-ptp project with a Status of InstallSucceeded.

      During installation an Operator might display a Failed status. If the installation later succeeds with an InstallSucceeded message, you can ignore the Failed message.

      If the operator does not appear as installed, to troubleshoot further:

      • Go to the Operators → Installed Operators page and inspect the Operator Subscriptions and Install Plans tabs for any failure or errors under Status.

      • Go to the Workloads → Pods page and check the logs for pods in the openshift-ptp project.

Configuring PTP devices

The PTP Operator adds the NodePtpDevice.ptp.openshift.io custom resource definition (CRD) to OpenShift Container Platform.

When installed, the PTP Operator searches your cluster for PTP-capable network devices on each node. It creates and updates a NodePtpDevice custom resource (CR) object for each node that provides a compatible PTP-capable network device.

Discovering PTP capable network devices in your cluster

  • To return a complete list of PTP capable network devices in your cluster, run the following command:

    $ oc get NodePtpDevice -n openshift-ptp -o yaml
    Example output
    apiVersion: v1
items:
- apiVersion: ptp.openshift.io/v1
  kind: NodePtpDevice
  metadata:
    creationTimestamp: "2022-01-27T15:16:28Z"
    generation: 1
    name: dev-worker-0 (1)
    namespace: openshift-ptp
    resourceVersion: "6538103"
    uid: d42fc9ad-bcbf-4590-b6d8-b676c642781a
  spec: {}
  status:
    devices: (2)
    - name: eno1
    - name: eno2
    - name: eno3
    - name: eno4
    - name: enp5s0f0
    - name: enp5s0f1
...
    1 The value for the name parameter is the same as the name of the parent node.
    2 The devices collection includes a list of the PTP capable devices that the PTP Operator discovers for the node.

Configuring linuxptp services as an ordinary clock

You can configure linuxptp services (ptp4l, phc2sys) as ordinary clock by creating a PtpConfig custom resource (CR) object.

Use the following example PtpConfig CR as the basis to configure linuxptp services as ordinary clock for your particular hardware and environment. This example CR also configures PTP fast events by setting appropriate values for ptp4lOpts, ptp4lConf and ptpClockThreshold. ptpClockThreshold is used only when events are enabled.
Prerequisites

  • Install the OpenShift CLI (oc).

  • Log in as a user with cluster-admin privileges.

  • Install the PTP Operator.

Procedure

  1. Create the following PtpConfig CR, and then save the YAML in the ordinary-clock-ptp-config.yaml file.

    apiVersion: ptp.openshift.io/v1
kind: PtpConfig
metadata:
  name: ordinary-clock-ptp-config                       (1)
  namespace: openshift-ptp
spec:
  profile:                                              (2)
  - name: "<profile_name>"                              (3)
    interface: ""<interface_name>"                      (4)
    ptp4lOpts: "-2 -s --summary_interval -4"            (5)
    phc2sysOpts: "-a -r -n 24"                          (6)
    ptp4lConf: |                                        (7)
     [global]
      #
      # Default Data Set
      #
      twoStepFlag                        1
      slaveOnly                          0
      priority1                          128
      priority2                          128
      domainNumber                       24
      #utc_offset                        37
      clockClass                         248
      clockAccuracy                      0xFE
      offsetScaledLogVariance            0xFFFF
      free_running                       0
      freq_est_interval                  1
      dscp_event                         0
      dscp_general                       0
      dataset_comparison                 G.8275.x
      G.8275.defaultDS.localPriority     128
      #
      # Port Data Set
      #
      logAnnounceInterval               -3
      logSyncInterval                   -4
      logMinDelayReqInterval            -4
      logMinPdelayReqInterval           -4
      announceReceiptTimeout             3
      syncReceiptTimeout                 0
      delayAsymmetry                     0
      fault_reset_interval               4
      neighborPropDelayThresh            20000000
      masterOnly                         0
      G.8275.portDS.localPriority        128
      #
      # Run time options
      #
      assume_two_step                    0
      logging_level                      6
      path_trace_enabled                 0
      follow_up_info                     0
      hybrid_e2e                         0
      inhibit_multicast_service          0
      net_sync_monitor                   0
      tc_spanning_tree                   0
      tx_timestamp_timeout               10             (8)
      unicast_listen                     0
      unicast_master_table               0
      unicast_req_duration               3600
      use_syslog                         1
      verbose                            0
      summary_interval                   0
      kernel_leap                        1
      check_fup_sync                     0
      #
      # Servo Options
      #
      pi_proportional_const              0.0
      pi_integral_const                  0.0
      pi_proportional_scale              0.0
      pi_proportional_exponent          -0.3
      pi_proportional_norm_max           0.7
      pi_integral_scale                  0.0
      pi_integral_exponent               0.4
      pi_integral_norm_max               0.3
      step_threshold                     2.0
      first_step_threshold               0.00002
      max_frequency                      900000000
      clock_servo                        pi
      sanity_freq_limit                  200000000
      ntpshm_segment                     0
      #
      # Transport options
      #
      transportSpecific                  0x0
      ptp_dst_mac                        01:1B:19:00:00:00
      p2p_dst_mac                        01:80:C2:00:00:0E
      udp_ttl                            1
      udp6_scope                         0x0E
      uds_address                        /var/run/ptp4l
      #
      # Default interface options
      #
      clock_type                         OC
      network_transport                  L2
      delay_mechanism                    E2E
      time_stamping                      hardware
      tsproc_mode                        filter
      delay_filter                       moving_median
      delay_filter_length                10
      egressLatency                      0
      ingressLatency                     0
      boundary_clock_jbod                0              (9)
      #
      # Clock description
      #
      productDescription                 ;;