Depending on the type of Gigabit Ethernet microwave link used to connect the Packet Microwave Adapter card and an MPR-e radio, different frequency synchronization mechanisms can be used.
When using optical 1000Base-SX to connect the Packet Microwave Adapter card and an MPR-e radio, synchronous Ethernet and SSM are the frequency synchronization mechanisms that are used. SSM is used as the mechanism to detect a microwave link failure, including loss of frame and MPR-e radio hardware failure.
When using electrical 1000Base-T to connect the Packet Microwave Adapter card and an MPR-e radio, PCR is the frequency synchronization mechanism that is used (a copper SFP is mandatory on ports 3 and 4).
For more information on PCR, synchronous Ethernet, and SSM, refer to the 7705 SAR Basic System Configuration Guide, ‟Node Timing”.