Dell SmartFabric OS10 User Guide Release 10.5.3

PDF

Configuration notes

The maximum number of supported PTP ports is 40.
Maximum number of supported PTP unicast masters is eight.
In a topology where a PTP device is connected to VLT primary and secondary nodes, configure PTP as an independent boundary clock on both the VLT nodes.
NOTE:
- Dell Technologies recommends enabling PTP on the VLT port channel member interfaces and not on the VLT port channel interface.
- Tagged PTP messages using the ptp vlan command are not supported on VLT port channel member interfaces.
- The unicast transport method is not supported on the VLT port channel member interfaces.
Reed-Solomon Forward Error Correction (RS-FEC) is enabled by default on optical modules in compliance with IEEE 802.3 standards. If the FEC latency is different on the switch and the peer PTP node, it can introduce a delay asymmetry and thereby cause time error. In this case, FEC can be disabled for the allowed link distance based on the optical module. With 25G-LR, FEC can be disabled up to the link distance of 500m SMF. With 25G-SR-NOF, FEC can be disabled up to the link distance of 30m (OM3) or 40m (OM4).

System time settings:

When you enable PTP as the system time source, PTP sets the system time. When you enable PTP on a system, the system cannot act as an NTP client, but can act as an NTP server.

NOTE: PTP system time configuration using the ptp system-time enable command is not required for boundary clock functionality. This command is used to set the following:

The switch local clock based on PTP timescale (International Atomic Time (TAI)).
The switch local clock in the timescale as received from master. If the received timescale is in PTP timescale, then the time on the switch local clock is set in PTP timescale (TAI) without converting to Universal Time Coordinated (UTC).

The following table describes the system clock behavior depending on whether you choose PTP or NTP as the system time source:

Table 1. System clock behavior
System time settings/time source	System clock behavior
When PTP is the system time source:	You cannot configure the system as an NTP client. If you configure the PTP clock and it is phase locked, PTP sets the time. If this time is set from a PTP master in PTP timescale, switch local time is bound to have TAI-UTC difference with UTC. If you do not configure the PTP clock and it is not phase locked, the free-running system clock sets the time.
When NTP is the system time source:	NTP client sets the system time. Even if the PTP clock runs on the system, PTP does not set the system time.
When you configure NTP as a server:	NTP provides the system clock. PTP or NTP can set the system clock.

You can configure PTP on the port channel interface and the port channel member interfaces.
- Port-channel interface: If the link aggregation is between two peer nodes, configure PTP on the port channel interface. The forward and reverse paths must be symmetrical for PTP. In this case, the links of the port channel need not be the same for both forward and reverse paths.
  NOTE: Dell Technologies recommends that you configure PTP on port channel member interfaces.
- Port-channel member interfaces: If the link aggregation spans across multiple nodes, configure PTP on the port channel member interfaces. PTP requires symmetrical forward and reverse paths. Therefore, configure PTP on the respective port channel member interfaces.
If you have configured PTP on an interface and use the interface breakout command, it removes the PTP configuration.
On boundary clocks, the interface breakout command removes the PTP port and changes the clock hierarchy.