The interval between Delay_Request messages is determined by the master clock. A parameter of the Delay_Response message sent from the master is the logMessagePeriod. This is a power of two value that defines a send window period designed to ensure that:
- Multiple slaves send at random intervals during the period.
- The master clock is able to respond to Delay_Requests from multiple slaves without queuing these messages.
So for a logMessagePeriod of 3:
sfptpd can override the logMessagePeriod value
using the config file option
sfptpd slave to send Delay_Request messages
at a fixed interval. The
ptp_delayreq_interval is also
a power of two value.
Ideally a slave server should sent Delay-Request messages at the same rate as it receives Sync/Follow_up messages thus ensuring that the four timestamps: T1-T4 are current when calculating the one-way-delay and offset values. Refer to Message Sequence above.