Accurate results for one-way and two-way delay measurement tests using Y.1731 messages are obtained if the nodes are capable of time stamping packets in hardware:
7210 SAS-Sx 10/100GE support is as follows:
Y.1731 2-DM messages for both Down MEPs and UP MEPs, 1-DM for both Down MEPs and UP MEPs, and 2-SLM for both Down MEPs and UP MEPs use software-based timestamps on Tx and hardware based timestamp on Rx. It uses the system clock (free-running or synchronized to NTP) to obtain the timestamps.
7210 SAS-T (network mode), 7210 SAS-Sx 1/10GE, 7210 SAS-Mxp, 7210 SAS-R6 and 7210 SAS-R12 support is as follows:
Y.1731 2-DM messages for both Down MEPs and UP MEPs, 1-DM for both Down MEPs and UP MEPs, and 2-SLM for both Down MEPs and UP MEPs use software-based timestamps on transmission and hardware-based timestamps on receipt. The timestamps are obtained as follows:
from NTP, when NTP is enabled and PTP is disabled
from PTP, when PTP is enabled (irrespective of whether NTP is disabled or enabled)
from PTP, when PTP is enabled and NTP is configured to use PTP for system time
from free-running system time, when both NTP and PTP are disabled.
The 7210 SAS-T (access-uplink mode) support is as follows:
Y.1731 2-DM messages for Down MEPs uses hardware timestamps for both Rx (packets received by the node) and Tx (packets sent out of the node). The timestamps is obtained from a free-running hardware clock. It provides accurate 2-way delay measurements and it is not recommended to use it for computing 1-way delay.
Y.1731 2-DM messages for UP MEPs, 1-DM for both Down MEPs and UP MEPs, and 2-SLM for both Down MEPs and UP MEPs use software based timestamps on Tx and hardware based timestamp on Rx. The timestamps are obtained as follows:
from NTP, when NTP is enabled and PTP is disabled
from PTP, when PTP is enabled (irrespective of whether NTP is disabled or enabled)
from PTP, when PTP is enabled and NTP is configured to use PTP for system time
from free-running system time, when both NTP and PTP are disabled.
On the 7210 SAS-T, 7210 SAS-Mxp, 7210 SAS-R6, 7210 SAS-R12 after PTP is enabled once, if the user needs to go back to NTP time scale, or system free-run time scale, a node reboot is required.