Ethernet Time Sync Properties

NI-XNET 19.1 Help

Edition Date: June 2019

Part Number: 372841W-01

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This category includes properties for the time synchronization protocol (IEEE Std 802.1AS) that operates on the XNET Interface. XNET refers to the synchronized time on the network as network time.

XNET uses the generic term clock for a distinct instance of the protocol that keeps synchronized time. You can think of the clock as representing the software (code) that is running in order to implement the protocol. IEEE Std 802.1AS refers to clock as a time-aware system.

XNET uses the generic term port to reference the physical port that exchanges protocol messages to synchronize time. Each clock contains one or more ports. In XNET, there is a one-to-one relationship between a time sync port and an XNET Interface. In IEEE Std 802.1AS-2011, a time-aware end station is a clock with one port, and a time-aware bridge is a clock with two or more ports. An Ordinary Clock in IEEE Std 1588-2008 is a clock with one port, and a Boundary Clock is a clock with two or more ports.

XNET uses the the term grandmaster to refer to the clock in the network that acts as the source of time for other clocks in the network. A clock that receives time from the grandmaster is a slave clock.

In the XNET Session, properties listed directly in the Time Sync category apply to the clock in the protocol. Properties listed in the Time Sync»Port category apply to a specific port of the clock, and the port corresponds to the current XNET Interface of the session.

By default, each XNET interface uses a distinct clock, and therefore the Time Sync properties and Time Sync»Port properties apply to the same entity. For example, for a 4-port Ethernet card using time synchronization protocol, each physical port runs as a time-aware end station by default, and the ports are unrelated to one another.


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