IEEE 1588v2 Precision Timing Protocol (PTP)

Starting with Junos OS Release 19.1R1, on QFX5110 switches, the IEEE 1588v2 Precision Time Protocol default profile supports aggregated Ethernet interfaces and the loopback interface using IPv4 and IPv6 unicast transport.The IEEE 1588v2 standard defines the Precision Time Protocol (PTP), which is used to synchronize clocks throughout a packet-switched network. This synchronization is achieved through packets that are transmitted and received in a session between a primary clock and a client clock or remote clock client. The clocks used for the distribution of accurate time are in an hierarchical primary/client architecture, which includes boundary clocks, ordinary clocks, and reference clocks. A boundary clock is both a clock source and a clock client. An ordinary clock is either a clock source or a clock client. However, a reference clock is always a clock source. An ordinary clock on a device is always a clock client. In addition, User UDP over IPv4 and unicast mode are used to transport PTP messages.

The following key PTP features are supported:

• Boundary clock—A boundary clock has multiple network connections and can act as a source (primary) and a destination (client or clock client) for synchronization messages. It synchronizes itself to a best primary clock through a client port and supports synchronization of clients to it on primary ports. Boundary clocks can improve the accuracy of clock synchronization by reducing the number of 1588v2-unaware hops between the primary and the client. Boundary clocks can also be deployed to deliver better scale because they reduce the number of sessions and the number of packets per second on the primary.

• Ordinary clock—The PTP ordinary clock has a single network connection and can act as a source (primary) or destination (client or clock client) for synchronization messages. On devices, the ordinary clock is a client, which receives synchronization reference messages from a primary, either a reference or a primary boundary clock. You cannot configure an ordinary primary on a device. However, a boundary clock can provide time to the ordinary client.

• PTP reference clock—The PTP reference clock communicates time information to destination or client ports. The reference clock is an external device to which the boundary or ordinary clock synchronizes. You cannot configure a reference clock on a device. However, a boundary clock client or an ordinary clock client can receive time from a reference clock.

• Clock source—A clock source is the PTP primary clock to which the client synchronizes. The clock source is included in the configuration of the client clock.

  Note:

  The term primary is sometimes used to refer to the clock source.

• Clock client—A clock client is the remote PTP host, which receives time from the PTP primary. The clock client is included in the configuration of the primary clock.

  Note:

  The term client is sometimes used to refer to the clock client.

• PTP over UDP over IPv4—The IEEE1588v2 standard specifies different transport protocols for carrying PTP packets. For example, PTP over Ethernet, PTP over UDP over IPv4, and PTP over UDP over IPv6. ACX Series routers support PTP over UDP over IPv4.

• Unicast mode (IPv4 on Gigabit Ethernet interfaces only)—Unicast mode is a user-to-user protocol used to send a datagram to a single recipient. Unicast mode is used for transporting PTP messages.

• 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.