Cisco Systems A9014CFD manual ClockClass Mapping, PTP Redundancy, Telecom Profiles, 22-40

Chapter 22 Configuring Clocking

Configuring PTP for the Cisco ASR 901 Router

If the T0 clock in Cisco ASR 901 is driven by the clock recovered from the OC Slave (if ToP0/12 is selected as clock-source), then the clock quality in the PTP parent dataset represents the quality of the ToP0/12 input clock. This should be informed to the netsync process for proper clock selection. This is done by translating clockClass data field in clock quality to QL-values expected by netsync.

On the other hand, if Cisco ASR 901 serves as the OC Master, then the GM clock is the clock providing T0 clock to Cisco ASR 901 router. Hence, the T0 clock quality should be used by OC master to fill up clockClass in the clock quality field, in its default dataset. For this, the T0 output QL-value should be mapped to the clockClass value according to ITU-T Telecom Profile, and set in the default dataset of the OC Master. This QL-value is then transmitted to the PTP slaves and BC downstream.

ClockClass Mapping

The Cisco ASR 901 router supports two methods of mapping PTP ClockClass to SSM/QL-value:

•Telecom Profile based on ITU-T G.8265.1/Y.1365.1 PTP (Telecom) Profile for Frequency Synchronization [2]

•Default method of calculating clockClass based on IEEE 1588v2 PTP specification.

Telecom Profiles

The Telecom Profile specifies an alternative algorithm for selecting between different master clocks, based on the quality level (QL) of master clocks and on a local priority given to each master clock. Release 3.11 introduces support for telecom profiles using a new configuration method, which allow you to configure a clock to use the G.8265.1 recommendations for establishing PTP sessions, determining the best master clock, handling SSM, and mapping PTP classes.

PTP Redundancy

PTP redundancy is an implementation on different clock nodes by which the PTP slave clock node achieves the following:

•Interact with multiple master ports such as grand master, boundary clock nodes, and so on.

•Open PTP sessions.

•Select the best master from the existing list of masters (referred to as the primary PTP master port or primary clock source).

•Switch to the next best master available in case the primary master fails, or the connectivity to the primary master fails.

Note The Cisco ASR 901 Series Router supports unicast-based timing as specified in the 1588-2008 standard. Hybrid mode is not supported with PTP 1588 redundancy.

	Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
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