SmartNIC Daisy Chain

Time-Stamping and Time Synchronization

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IntelĀ® PAC
Napatech SmartNIC
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User Guide

Illustration

This figure shows a configuration with 3 NT SmartNICs, where one SmartNIC, NT SmartNIC #1, acts as a master for the two other SmartNICs. In this example the master SmartNIC is synchronized to OS time, but this is an optional configuration.

3 NT SmartNICs, where one SmartNIC, NT SmartNIC #1, acts as a master for the two other SmartNICs

The time stamp clock of NT SmartNIC #1 provided via the output time synchronization connector is used as reference for NT SmartNICs #2 and #3. SmartNICs #2 and #3 are both configured to repeat the NT-TS signal from the input time synchronization connector (TS In) to the output time synchronization connector (TS Out), and to synchronize the SmartNIC time stamp clock to the NT-TS signal received on the input time synchronization connector.

Compensation for the delay in the time synchronization cables and the daisy chain delay (TimeSyncTimeOffset) must be made for SmartNICs #2 and #3. A time synchronization cable length of 0.2 meters is used for all internal cables in the configuration in this section, and it is assumed that all SmartNICs are NT20E3-2-PTP SmartNICs (see Signal Delay Compensation Example 1). See Compensating for Signal Delays for details on delays.

ntservice.ini configuration

These ntservice.ini code lines configure NT SmartNIC #1 for the setup in Illustration.

TimeSyncReferencePriority=OsTime
TimeSyncConnectorInt2=NttsOut

These ntservice.ini code lines configure NT SmartNIC #2 for the setup in Illustration.

TimeSyncConnectorInt1=NttsIn
TimeSyncReferencePriority=Int1,OsTime
TimeSyncConnectorInt2=RepeatInt1
TimeSyncTimeOffset=15

These ntservice.ini code lines configure NT SmartNIC #3 for the setup in Illustration.

TimeSyncConnectorInt1=NttsIn
TimeSyncReferencePriority=Int1,OsTime
TimeSyncConnectorExt1=RepeatInt1
TimeSyncTimeOffset=30