PTP - Interface Roles

When configuring the Precision Time Protocol (PTP) there are specific roles that are assigned to the interfaces connecting PTP devices. Depending upon the clock type of each device, the interface role is assigned so that the master interface is closer to the Best Master Clock. The PTP Best Master Clock Algorithm (BMCA) is involved in making the determination.

Take a look at this diagram:

The interface roles are indicated using "M" for master and "S" for slave. Notice that the M interfaces are closer to the GMC which is the authoritative time source. Thus time synchronization takes place from M to S interfaces all the way down to the OCs.

Note that devices that are assigned the Transparent Clock type do not have M or S interfaces. This is illustrated in the following diagram:

Links:

https://forum.networklessons.com/t/introduction-to-precision-time-protocol-ptp/39658/11?u=lagapidis

https://networklessons.com/cisco/ccnp-encor-350-401/introduction-to-precision-time-protocol-ptp