This attribute is the 64 bit value of the Timestamp that was sent by the CMTS in the PLC frame containing the Trigger Message Block. This attribute is a copy of the 64-bit DOCSIS 3.1 extended timestamp defined in [MULPI3.1 paragraph 7.1.5, Extended Timestamp]. Bit 0 is the LSB and bit 63 is the MSB. For this measurement, the accuracy in reading the timestamp by the CM is expected to be 100 ms or better. Hence for practical purposes, bits 0-20 may not be meaningful. Bit 21 provides a resolution (not accuracy) of 0.4 ms, and bit 63 has a rollover period of approximately 112 years.