Applying a PTP Delay Mechanism

Time-Stamping and Time Synchronization

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IntelĀ® PAC
Napatech SmartNIC
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User Guide

In this section

This section describes how to apply a PTP delay mechanism.

PTP delay mechanisms

The PtpDelMech parameter specifies one of the two PTP delay mechanisms supported for propagation delay measurements: End-to-end (delay request-response mechanism) and peer-to-peer (peer delay mechanism).

Note: For the PTP Telecom profile and the PTP Enterprise profile the parameter can only take one value, namely E2E.For the PTP Power profile the parameter can only take one value, namely P2P.

End-to-end (E2E)

This mechanism uses a message exchange (delay-request-response) method between slave and master. The slave sends a delay request message to the master, which in turn responds with a delay response message back to the requesting slave. The propagation path between the two endpoints might or might not be PTP-aware switches/hubs/routers and so on.

Peer-to-peer (P2P)

This mechanism uses a port-based peer delay message mechanism. Each port on a PTP device sends peer delay request messages to the port it is directly connected to. The connected port then responds with a peer delay response message. The requesting port finally stores the propagation delay measured between the 2 ports. All ports in a PTP-aware network must use the same delay mechanism. This implies that only complete PTP-aware networks can use the P2P delay mechanism. Furthermore, P2P is often mentioned when the capability of a PTP-transparent clock device is specified since such devices are required in a switched/routed network using the P2P mechanism.

The final calculation of the propagation delay between master and slave is done by each transparent clock (switch, hub or router) by adding the receiving port peer delay and the residence time of the packet in the device to the correction field of the PTP event message, for instance a synchronization message. In this way sudden changes in the propagation path have a very small impact on the synchronization of slaves.

ntservice.ini code line

The syntax for the ntservice.ini code line applying a PTP delay mechanism is:

'PtpDelMech' '=' ( 'E2E' | 'P2P' )

Example:

PtpDelMech=P2P

Default value

This table shows the default value.

Parameter Default Value
PtpDelMech

For the PTP Default, Telecom and Enterprise profiles:

E2E

For the PTP Power profile:

P2P