// Module included in the following assemblies:
//
// * networking/advanced_networking/ptp/configuring-ptp.adoc

:_mod-docs-content-type: CONCEPT
[id="nw-ptp-granite-rapids-boundary-clock-overview_{context}"]
= Boundary clocks without holdover on Intel Granite Rapids-D hardware

[role="_abstract"]
Intel Granite Rapids-D (GNR-D) server platforms support Precision Time Protocol (PTP) boundary clock (BC) deployments without holdover for high-density Radio Access Network (RAN) sites that use onboard Network Acceleration Complex (NAC) ports and optional Carter Flat expansion network interface cards (NICs).

In a BC deployment, one time receiver (TR) port synchronizes to an upstream timing source while time transmitter (TT) ports distribute synchronized time to downstream devices. GNR-D platforms use platform-specific `PtpConfig` plugin configurations and internal timing paths.

Before you configure a BC profile on GNR-D hardware, verify that your qualified hardware layout, interface naming, and plugin configuration align with your deployment requirements.

GNR-D BC deployments use onboard NAC ports as the primary timing controller and can extend timing distribution by using optional Carter Flat expansion NICs. 

GNR-D platforms route synchronization internally instead of using external timing cabling. 

Your qualified hardware layout determines the available TR and TT port roles across NAC ports and optional Carter Flat expansion cards.

[id="nw-ptp-granite-rapids-boundary-clock-overview-without-holdover_{context}"]
== Boundary clock without holdover behavior

GNR-D boundary clock deployments on Carter Flat hardware do not maintain time synchronization if the upstream timing source becomes unavailable. This deployment model operates without monitored holdover because Carter Flat hardware does not expose sufficient follower digital phase-locked loop (DPLL) accuracy information for holdover support.

To maintain synchronization, keep a continuous connection to a qualified upstream PTP source.

Red Hat tools can detect follower DPLL lock state, but they cannot monitor the detailed follower DPLL accuracy that holdover support requires.

When you configure a BC profile on GNR-D hardware that uses Carter Flat NICs, disable holdover.