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PTP Master/Slave [1204-12] (Obsolete)

Precision Time Protocol (PTP) is a protocol that can be used to synchronize computers on an Ethernet network. The 10/100 PTP Master/Slave option card supports PTP Version2, as specified in the IEEE 1588-2008 standard (PTP Version 1 is not supported), via one (1) Ethernet port.

The PTP option card implements a PTP Ordinary Clock that can be configured to run as:

  • A Master Clock, in which case it transmits PTP packets via the Ethernet port, with information about the current time and synchronization reference selected by SecureSync.
  • A Slave Clock, in which case it provides to the SecureSync device a time and synchronization reference retrieved from information carried by the PTP packets received via the Ethernet port.
  • A Master/Slave Clock, in which case the PTP option card can change mode according to priority and quality criteria compared with the other PTP Clocks on the network.

PTP Master/Slave[1204-12]: Specifications

  • Inputs/Outputs: (1) Configurable as Input or Output
  • Signal Type and Connector: RJ-45
  • Management: Web UI
  • Resolution: 8ns (±4ns) packet time stamping resolution
  • Accuracy: 30 ns accuracy (3σ) Master to Slave, via crossover cable
  • Networking speeds: 10 Mb/s, 100 Mb/s
  • Supported PTP Versions: PTP 2 (IEEE 1588-2008)

  • PTP Profiles supported: Default

  • Transmission modes: Unicast, Multicast [default]
  • Maximum Number of Cards: 6
  • Ordering Information: 1204-12: PTP/Precision Timing Protocol Option Module

Model 1204-12 option card rear plate

PTP Master/Slave [-12]: Edit Window

  1. To configure this option card, go to its Edit window. For instructions, see Configuring Option Card Inputs/Outputs.
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    • Note: If you have only one input or output of any type, SecureSync will number that input or output 0. Additional inputs or outputs will be numbered 1 or above.

    1. The PTP Edit window will display. It offers access to four different tabs, described below:

    Main tab settings

    Settings to configure under the Main tab:

    • Transmission Mode: (See also: Transmission Modes)
      • Unicast
      • Multicast
      • Minicast
    • Clock Mode: The Master/Slave Mode of the PTP Module. Will be one of:
      • Slave
      • Master
      • Disabled

      The default value is Slave.

    • Domain Number: Sets the current PTP Domain Number, as defined in IEEE Std 1588-2008 Section 7.1. Range: [0,255]. Default setting: 0
    • Master Clock IP Address: Static IP address of the unicast Master Clock. In the format “#.#.#.#” with no leading zeroes or spaces, where each ‘#’ is a decimal integer from the range [0,255].

    Ethernet tab settings

    Settings to configure under the Ethernet tab:

    • Transport Protocol: Selects the transport protocol used for PTP Packets. Possible values are:
      • IPv4 (The default): Internet Protocol version 4 (Layer 3 protocol).
      • 802.3/Ethernet: IEEE802.3/Ethernet Protocol (Layer 2 protocol).

      Operating limitations: The IEEE802.3/Ethernet Protocol is not supported in Unicast transmission mode.

    • Enable DHCP: This is a checkbox to enable or disable the delivery of IP addresses from a DHCP Server. The default setting is enabled (the box is checked).
    • Static IP Address: When a DHCP server is not requested or is requested but not available, the PTP Module will use this IP address. In the format “#.#.#.#” with no leading zeroes or spaces, where each ‘#’ is a decimal integer from the range [0,255].
    • Network Mask: When a DHCP server is not requested or is requested but not available, the PTP Module will use this Network Mask. In the format “#.#.#.#” with no leading zeroes or spaces, where each ‘#’ is a decimal integer from the range [0,255].
    • Default Gateway: When a DHCP server is not requested or is requested but not available, the PTP Module will use this Default Gateway. In the format “#.#.#.#” with no leading zeroes or spaces, where each ‘#’ is a decimal integer from the range [0,255].

    Contract tab settings

    Note: The settings under this tab only apply to Unicast Mode.

    Settings to configure under the Contract tab:

    • Min Sync Interval: The minimum value of Sync interval granted by the Master Clock. In packets per second.
    • Max Sync Duration: The maximum value of Sync interval granted by the Master Clock. In seconds.
    • Min Announce Interval: The minimum value of the Announce interval granted by the Master Clock. In packets per second.
    • Max Announce Duration: The maximum value of the Announce interval granted by the Master Clock. In seconds.
    • Min Delay_Req Interval: In packets per second.
    • Max Delay_Req Duration: In seconds.
    • Max Slaves: The maximum number of slaves the card will serve.

    Advanced tab settings

    Settings to configure under the Advanced tab:

    • Synchronization Mode: Determines the number of steps in the PTP protocol. Will be either 1-Step Mode, or 2-Step Mode.
    • Delay Mechanism: Determines how the protocol calculates delay [Default: End-to-End]
    • Time-To-Live (Packet Lifespan): Ethernet characteristic, determining the number of routers a packet will go through [Spectracom default: 64].
    • Name: Assign a name to this option card (Note: Used only by Managament Profile]
    • Location: Assign a location to this option card (Note: Used only by Managament Profile]

    PTP Master/Slave [-12]: Status Window

    To view the status of a PTP interface, go to its Status window. For instructions, see Viewing Input/Output Configuration Settings.

    The GB PTP Status window contains two tabs: Main and Advanced.

    Main tab: Status information

    The Main tab provides the following information:

    • Ethernet Status: Whether the module is connected to a network through Ethernet.
      • Green=Connected. The speed of the connection is indicated.
      • Orange=Not connected.
    • Status: Master/Slave mode of the card.
    • Transmission/Clock Mode: Transmission mode and master/slave mode.
    • Domain Number: The current PTP Domain Number.
    • Current IP Address: The IP address currently being used by the PTP interface.
    • MAC Address: The MAC address currently being used by the PTP interface.

    Advanced tab: Status information

    The Advanced tab provides the following information:

    Time Properties:

    • UTC Offset: The Master’s current offset between UTC time and TAI time. Units: seconds.
    • UTC Offset Valid: Indicates whether or not the Master’s UTC Offset is valid.
    • Leap Second: The Leap second correction as set on the Time Management page.
    • Time Traceable: Indicates whether the Master’s time is traceable (Enabled) to a primary reference or not (Disabled).
    • Frequency Traceable: Indicates whether the Master’s Frequency is traceable (Enabled) to a primary reference or not (Disabled).
    • PTP Time Scale: Indicates the timescale that the Master is using to broadcast its time. TAI is the default PTP timescale.
    • Time source: The Time Source that the Master is using. Refer to IEEE Standard 1588-2008, Section 7.6.2.6.

    Clock Quality

    • Clock Accuracy: A number describing the accuracy of the oscillator in the Master relative to its UTC reference. (See IEEE Standard 1588-2008, Section 7.6.2.5).
    • Offset Scaled Log Variance: (Defined in IEEE Standard 1588-2008, Section 1.6.3)
    • Clock Class: A number describing the state of the time and 1pps references of the PTP Clock.

      Refer to the following table for Clock Class information (see IEEE standard 1588-2008, Table 5, Section 7.6.2.4).

    PTP Time Scale Arbitrary Time Scale Clock Class Definition
    6 13 Time and 1pps references are synchronized with the host references and PTP clock shall not be a slave to another clock in the domain.
    7 14 Time and 1pps references are in holdover state, within specifications and PTP clock shall not be a slave to another clock in the domain.
    52 58 Time and 1pps references are in holdover state, not within specifications, and PTP clock shall not be a slave to another clock in the domain. Then, applied to Master Clocks who have just powered on and have not yet achieved a suitable TFOM value.
    187 193 Time and 1pps references are in holdover state, not within specifications, and PTP clock may be a slave to another clock in the domain.
    255 255 Class assigned to “Slave-Only” clocks.
    248 248 “Unknown” class.

    Clock Class definitions

    Ethernet Status

    • Current IP Address: The IP address currently being used by the PTP interface.

      Note: If the PTP Module is set up for DHCP but fails to obtain an IP address, it will use the Static IP instead. To reacquire a DHCP address, reset the module via the Main tab in the PTP settings window.

    • Current Network Mask: The Network Mask currently being used by the PTP interface.
    • Current Gateway: The Gateway address currently being used by the PTP interface.

    Port Status

    • Port Number: The PTP Port Number, as defined in the IEEE 1588-2008 Specification, Section 7.5.2.3. Always set to 1 for our Ordinary Clock.
    • Port Activity: Reports whether or not the network interface is active for PTP (Enabled) or not (Disabled).
    • Port State: Reports the current state of the PTP State Machine:
      • Disabled: PTP Ethernet port is Disabled. See PTP Setup/Network page, PTP Network Settings options.
      • Initializing: Ethernet link is unplugged/PTP Module is in power-up state. A Master Clock doesn’t leave this state while it can’t get the current time and synchronization references from the SecureSync to synchronize with it.
      • Listening: PTP module is looking for a Master Clock.
      • Master: PTP Master has become the active Master Clock on the network.
      • Passive: PTP Module has become a Passive Master Clock. (There is another Master Clock on the network with better quality or higher priority). This Master will wait until the Best Master Clock Algorithm determines it should become the best Master Clock, and then it will transition to the Master Clock state.
      • Uncalibrated: PTP Slave has selected a Master Clock on the network attempts to synchronize with it using sync packets.
    • Link Status: Indicates whether or not the Ethernet link for PTP is active (Connected) or not (Disconnected).
    • Slave Sync Mode: Determines the number of steps in the PTP protocol. Will be one of the following:
      • Two-Step Mode
      • One-Step Mode

        Note: One-Step mode is not supported with the Peer-to-Peer Delay Mechanism.

        The current implementation of one-step mode involves a software-oriented timestamping. Two-step mode implements a hardware oriented timestamping, insensitive to software execution time variations. Two-step mode is recommended, as it increases the PTP Clock’s accuracy.

    Note: Peer-to-Peer Delay Mechanism is only applicable on networks equipped with Transparent Clocks (switches/routers IEEE 1588 compatible). Peer-to-Peer Delay Mechanism is not supported in Unicast transmission mode.

    Grandmaster Properties

    Reports information from the current Grandmaster Clock. If the PTP Module is currently a Master, this will report information on the current module.

    • Clock Identity: Displays the clock identity of the current Grandmaster Clock on the network.
    • Clock Class: A number describing the state of the clock (see Table 5 of Section 7.6.2.4 of IEEE Standard 1588-2008).
    • Clock Accuracy: A number describing the accuracy of the oscillator in the Grandmaster Clock (see IEEE Standard 1588-2008, Section 7.6.2.5).
    • Offset Scaled Log Variance: See IEEE Standard 1588-2008 Section 7.6.3.
    • Priority1: See IEEE Standard 1588-2008, Section 7.6.3.
    • Priority2: See IEEE Standard 1588-2008, Section 7.6.3.

    Slave Properties

    • Negotiation Enabled: Reports whether the Unicast Negotiation option is Enabled or Disabled.
    • Contract State: Reports the unicast contract state.
      • NEGO_OFF: Unicast negotiation option is Disabled.
      • NEGO_ON: Unicast negotiation option is Enabled.
      • REQUESTED: Unicast contract has been requested to the PTP Master.
      • GRANTED: Unicast contract has been granted by the PTP Master.
      • RENEWED: Renewal of the unicast contract has been requested to the PTP Master.
      • CANCELED: Cancellation of the unicast contract has been requested to the PTP Master.
    • Contract Duration: Duration of the unicast contract. Units: Seconds.
    • Contract Delay: Delay before the end of the unicast contract. Units: Seconds.
    • Message Interval: Announce Interval negotiated for the unicast mode. Units: log2 seconds.
    • Contract State: Reports the unicast contract state (see above ‘Announce Contract State’).
    • Contract Duration: Duration of the unicast contract. Units: Seconds.
    • Contract Delay: Delay before the end of the unicast contract. Units: Seconds.
    • Message Interval: Sync Interval negotiated for the unicast mode. Units: log2 seconds.
    • Contract State: Reports the unicast contract state (see above ‘Announce Contract State’).
    • Contract Duration: Duration of the unicast contract. Units: Seconds.
    • Contract Delay: Delay before the end of the unicast contract. Units: Seconds.
    • Log Message Interval: Delay_Resp Interval negotiated for the unicast mode. Units: log2 seconds

    Master Properties

    • Unicast Negotiation: Reports whether the Unicast Negotiation option is Enabled or Disabled.
    • Number of Slave Clocks Connected: Number of PTP Slaves that have been granted by the PTP Master to run in unicast mode (maximum = 128 unicast contracts).

    Module Info

    • PTP Version: Current version of PTP being used.
    • Software Version: Current software revision level
    • Hardware Version: Current hardware revision level.
    • Software Compilation Date: Date the software was compiled.
    • Software Compilation Time: Time the software was compiled

    Configuring the [-12] PTP Master/Slave Card

    Configuration as a Slave Clock

    By default, the PTP card is configured to function as a Multicast PTP Slave, which allows a SecureSync to be able to synchronize to a Multicast PTP Master (such as another SecureSync unit with a PTP module option card configured as a Master) when configured with the following parameters:

    • Announce Interval = once every 4 seconds or faster (This is set in the PTP Edit window, under the Contract tab).
    • Delay Mechanism = End-to-End (This is set in the PTP Edit window, under the Advanced tab).
    • Transmission Mode = Multicast (This is set in the PTP Edit window, under the Main tab).
    • Synchronization Mode = Two-Step Mode faster (This is set in the PTP Edit window, under the Advanced tab).

    When first connected to a network that contains an active Master Clock, it may take up to a minute for the Port State to change to the “slave” state. After that, it will take up to two minutes for the PTP connection to be accepted as a valid reference by SecureSync.

    If SecureSync is not entering the “Slave” Port state (as reported by the Main tab on the PTP Status page), check the following:

    • From the PTP Status window under the Main tab, check that Ethernet Status indicates “Connected.”
    • From the PTP Status window under the Advanced tab, check that Port Activity indicates “Enabled.”
    • From the PTP Status window under the Main tab, check that the Ethernet Status indicates a speed of 100 Mb/s.
    • From the PTP Status window under the Main tab, check that the clock is set to be a Slave Only.
    • From the PTP Status window under the Main tab, check that the Transmission/Clock Mode is a Slave mode and that multicast/unicast/minicast state is correct.
    • Check that the Ethernet Transport Protocol set for the Slave Clock is the same as the Transport Protocol of the Master Clock to which the Slave Clock must be synchronized with. (Check the Transport Protocol on the PTP Edit window, under the Ethernet tab.)
    • Check that the Domain Number set for the Slave Clock is the same as the Domain Number of the Master Clock to which the Slave Clock must be synchronized with. (Check the Domain Number on the PTP Status window, under the Main tab.)
    • From the PTP Status window, under the Advanced tab, check that the Current IP Address is valid.
    • From the PTP Edit window under the Advanced tab, check that the Time To Live (TTL) for PTP packets is compatible with the network.
    • If in Multicast mode, check that the switches/routers are transparent to multicast frames
    • From the PTP Status window under the Advanced tab, check that the Clock Class is “Master, In Sync.”

    Note: If DHCP is enabled and PTP was not successful in obtaining an IP address, DHCP will need to be restarted to retry. To restart DHCP:

    1. In the PTP Edit window under the Ethernet tab, select the Enable DHCP checkbox.
    2. Click the Submit button at the bottom of the window.

    Configuration as a Master Clock

    To configure the IEEE-1588 (PTP) Module as a Master Clock, perform these steps:

    General configuration steps:

    • Ensure the PTP port is connected to the network (check the Link Status in the PTP Status/Network page).
    • Ensure the PTP port speed is 100 Mb/s (check the Port Speed in the PTP Status page under the Advanced tab).
    • Be sure that valid time and 1PPS references are currently selected (go to MANAGEMENT/OTHER/Time Management).

    In order to operate properly as a Master Clock, SecureSync must be synchronized to a non-PTP reference. Confirm that the chosen reference transmits the following information (as reported by the Time Properties on the PTP Status page, under the Advanced tab):

    • The proper TAI or UTC time (including the current year)
    • The current TAI to UTC offset (required even if the reference’s time is in TAI)
    • Pending leap second information at least a day in advance.

    If the reference does not transmit this information, it must be provided by the user in order for the Master Clock to function properly.

    The built-in GNSS reference provides all information needed with no user intervention.

    PTP-specific configuration steps:

    Confirm that:

    • From the PTP Status window under the Advanced tab, check that PTP Port Activity is enabled (if not, enable it from the PTP Edit window, under the Ethernet tab).
    • From the PTP Edit window under the Main tab, check that the clock is set to be a Master.
    • From the PTP Status window under the Main tab, check that a valid IP address is currently being used.

    When the PTP Module is set to be a Master Clock, the module will immediately attempt to become the active Master Clock on the network (Port State = Master). If it does, it will start to transmit PTP packets (even if the SecureSync is not yet synchronized).

    There are several reasons why the PTP Module may not become the active Master Clock, or may not be broadcasting the correct time, even if it is set to be a Master Clock:

    1. If using any reference other than self for 1PPS, the SecureSync will not become an active Master Clock until the Time Figure of Merit (TFOM) value of the system is less than 15. After first going into sync after power-up, it may take a minute or two for the Time Figure of Merit (TFOM) value to fall to an acceptable level. The current Time Figure of Merit (TFOM) value is available in the Time Properties panel under the Advanced tab on the PTP Status window page.
    2. PTP uses the TAI timescale to transfer time. Many timing references communicate time in the UTC timescale. UTC is offset from TAI by a small amount which changes every time a leap second occurs. The TAI to UTC Offset is part of the PTP Specification and must be provided to a Master Clock. If no active reference can provide that information, the offset must be provided by the Host. The TAI to UTC Offset can be set from the MANAGEMENT/OTHER/Time Management page (while setting the GPS to UTC Offset).
    3. The PTP Protocol also provides for the transfer of Leap Second information. If the active time reference does not provide Leap Second information, it must be added by the user through the MANAGEMENT/OTHER/Time Management page. If this is not done, the PTP network will have the incorrect UTC time after a leap second event.
    4. If there are multiple multicast Master Clocks on the network, the PTP Module uses the Best Master Clock (BMC) algorithm specified in the PTP Specification to decide whether or not to become the active Master Clock. The BMC algorithm selects the Best Master Clock on the network from the following criteria:
      1. The BMC algorithm first selects the clock having the higher Priority1 parameter (a lowest value means a higher priority)
      2. If the BMC cannot be determined from the previous parameter, the BMC algorithm selects the clock having the higher Clock Quality (Clock Class, Clock Accuracy, Clock Variance)
      3. If the BMC cannot be determined from the previous parameters, the BMC algorithm selects the clock having the higher Priority2 parameter

    The Master Clock selected by the BMC algorithm as the Best Master Clock will transition into the Master state to become the active Master Clock on the network. It will then start to transmit Sync packets to the Slave Clocks. The other Master Clocks will transition into the Passive state.

    Configuring Unicast Mode

    For information on Unicast mode, see Transmission Modes.

    The unicast mode is activated at the initiative of the Slaves. Each Slave, which wants to run in unicast mode, shall first negotiate unicast contracts with the Master.

    To enter the Unicast mode, perform the following steps:

    On the Master side:

    • In the PTP Edit window under the Main tab, select Multicast for the Transmission Mode. Enable the Unicast mode.

    On the Slave side:

    • In the PTP Edit window under the Main tab, select Multicast for the Transmission Mode. Enable the Unicast mode.

    When the Master Clock is set in multicast mode, this one will deny the requests from the Slaves Clocks to run in Unicast mode.

    When the Master Clock is set in Unicast mode, it does not transmit any PTP messages until a Slave has been granted to run in Unicast mode.

    The Model 1204-12 card can grant up to 128 Unicast contracts (i.e., it can handle up to a total of 128 PTP clients). [Note that the 1204-32 Gb PTP card can handle up to 4000 Unicast contracts.]

    The Model 1204-12 does not support mixing Unicast and Multicast clients on the same domain (Unlike the 1204-32 Option Card). When using the 1204-12 PTP card with Unicast clients, all clients need to be configured to use Unicast mode.

    Note: The Unicast mode is only implemented for the following PTP packets:

    - Announce

    - Sync and Follow-Up

    - Delay_Req and Delay_Resp

    Configuring Master/Slave Mode

    The PTP Master/Slave option card [-12] also supports a combined Master/Slave mode. The Master/Slave mode works best in a SecureSync which is not synchronized to any other reference. When the module is plugged into the PTP network, it will become a slave to the Best Master Clock on the network.

    If all Master Clocks are removed from the network, the SecureSync containing the Master/Slave module will go into Holdover mode. However, the module will use that Holdover time to become the Best Master Clock on the network, and it will provide time to the network until the SecureSync’s Holdover Timeout expires. If another Master Clock comes online and becomes the Best Master Clock, the Master/Slave module will become a Passive Master Clock until the SecureSync’s Holdover Timeout expires.

    For more information on Holdover Mode, refer Holdover Mode.

    Note: The Master/Slave mode is NOT supported in Unicast transmission mode.

    Configuring Minicast Mode

    For information on Minicast mode, see Transmission Modes.

    On the Master side:

    • In the PTP Edit window under the Main tab, select Multicast for the Transmission Mode. Enable the Minicast mode.

    On the Slave side:

    • In the PTP Edit window under the Main tab, select Multicast for the Transmission Mode. Enable the Minicast mode.

    Transmission Modes

    Multicast Mode

    This is the default mode. PTP packets are transmitted to all PTP Clocks by means of multicast IP addresses dedicated to the PTP protocol (224.0.1.129, 224.0.0.107). PTP packets received by the PTP Clocks are then filtered from the Domain Number, the Port Identity (Clock Identity + Port Number) of the transmitter, the packet identifier (Sequenced).

    When the Master Clock is set in multicast mode, this module will deny the requests from the Slaves Clocks to run in unicast mode.

    When the Master Clock is set in Unicast mode, it doesn’t transmit any PTP messages until a Slave has been granted to run in unicast mode.

    Unicast Mode

    This is a Point-to-Point transmission mode between two PTP Clocks by means of the unique IP address assigned to each PTP Clock.

    Note: The Unicast mode is only implemented for the following PTP packets:

    - Announce

    - Sync and Follow-Up

    - Delay_Req and Delay_Resp

    The Unicast mode is activated at the initiative of the Slaves. Each Slave, which wants to run in unicast mode, shall first negotiate Unicast contracts with the Master.

    Minicast/Hybrid Mode

     The Minicast/Hybrid mode is a method to minimize the PTP packets payload on the network, where:

    • The transmissions initiated by the Master (Announce, Sync/Follow-Up) run in multicast mode.
    • The transmissions initiated by the Slaves (Delay_Req/Delay_Resp) run in unicast mode.