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ME60 V800R010C10SPC500 Feature Description - System Management 01

This is ME60 V800R010C10SPC500 Feature Description - System Management
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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Basic Concepts

Basic Concepts

Clock Source

The device that provides clock signals for another device is called a clock source. A device can have multiple clock sources. They are classified into the following types:

  • External clock source

    An external clock source traces a high-level clock through the clock interface provided by a clock board.

  • Line clock source

    A clock board uses Ethernet interfaces to extract clock signals from Ethernet line signals or STM-N line signals.

  • Internal clock source

    The reference clock provided by the local device, for example, the clock provided by a clock board, is used as the working clock of an interface.

Reference Factors for Clock Source Selection

The ME60 can select a clock source based on three reference factors: priorities, synchronous status message (SSM) levels, and clock IDs of clock sources.

Clock Source Selection Modes

The ME60 supports the following clock source selection modes:
  • Automatic clock source selection: The ME60 uses the automatic clock source selection algorithm to determine a clock source to be traced based on priorities, SSM levels, and clock IDs of clock sources.

  • Manual clock source selection: A clock source to be traced is manually specified. This clock source must have the highest SSM level.
  • Forcible clock source selection: A clock source to be traced is forcibly specified. This clock source can be any clock source.
NOTE:

You are advised to configure the automatic clock source selection mode. In this mode, the ME60 dynamically selects an optimal clock source based on clock source quality.

ME60

SSM

The International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) defined a synchronous status message (SSM) to identify the quality level of a synchronization source on synchronous digital hierarchy (SDH) networks. As stipulated by the ITU-T, the four spare bits in one of the five Sa bytes in a 2 Mbit/s bit stream are used to transmit the SSM value. The use of the SSM value in clock source selection brings the following benefits:
  • Improves synchronization network performance.
  • Prevents timing loops.
  • Achieves synchronization on networks with different structures.
  • Enhances synchronization network reliability.

Forcible Participation of SSM Levels in Clock Source Selection

In automatic clock source selection mode, you can configure SSM levels to forcibly participate in clock source selection. After the configuration is complete, the ME60 determines a clock source to be traced based on priorities and SSM levels of clock sources. The ME60 determines the SSM level of each clock source and preferentially selects a clock source with the highest SSM level. If two or more clock sources have the same SSM level, the ME60 selects a clock source based on the priorities of these clock sources.

Extended SSM

The extended SSM function enables clock IDs to participate in automatic clock source selection. This function prevents clock loops.

When the extended SSM function is enabled, the ME60 does not allow clock IDs to participate in automatic clock source selection in either of the following cases:

  • The clock ID of a clock source is the same as the clock ID configured on the ME60.
  • The clock ID of a clock source is 0.
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Updated: 2019-01-04

Document ID: EDOC1100059466

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