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Configuration Guide - Device Management

CloudEngine 8800, 7800, 6800, and 5800 V200R005C10

This document describes the configurations of Device Management, including device status query, hardware management, Information Center Configuration, NTP, Synchronous Ethernet Configuration, Fault Management Configuration, Energy-Saving Management Configuration, Performance Management Configuration, Maintenance Assistant Configuration, and OPS Configuration.
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Basic Concepts of 1588v2

Basic Concepts of 1588v2

A time synchronization network is a network that implements time synchronization between network devices. Figure 6-1 shows the architecture of a time synchronization network. This network uses a two-level architecture. Level-1 nodes are level-1 time synchronization devices; level-2 nodes are level-2 time synchronization devices; nodes below level-2 nodes are clients that require time synchronization, such as servers.

Figure 6-1 Time synchronization network hierarchy

Clock Synchronization

On a modern communications network, most telecommunications services require that the frequency deviation or time difference between devices be within an acceptable range. This requirement must be met using network clock synchronization.

Network clock synchronization includes frequency synchronization and phase synchronization.

  • Frequency synchronization, also called clock synchronization

    Frequency synchronization indicates that signals have the same frequency and a fixed phase difference. That is, signals are sent or received at an average rate. All devices on a communications network operate at the same rate.

  • Phase synchronization, also called time synchronization

    Phase synchronization indicates that both frequencies and phases of signals are consistent. That is, the phase offset between signals is always 0.

Figure 6-2 illustrates the difference between frequency synchronization and phase synchronization. If Watch A and Watch B show different time but they keep a constant time difference, this is called frequency synchronization. If Watch A and Watch B always keep the same time, this is called phase synchronization.

Figure 6-2 Difference between frequency synchronization and phase synchronization

PTP Domain

A PTP domain is a logical area that runs PTP. There may be multiple PTP domains on a network. Each PTP domain has only one clock source, and all devices in a PTP domain synchronize the time with this clock source. Each clock domain has its own synchronization time and runs independently of each other.

Clock Node

Clock nodes are nodes in a PTP domain. Currently, switches support only two clock node types defined in 1588v2:
  • Ordinary clock (OC)

    An OC provides only one physical port to participate in PTP time synchronization in a PTP domain. An OC uses this port to synchronize the time with an upstream device or to synchronize the time to downstream devices.

  • Boundary clock (BC)

    A BC provides two or more physical ports to participate in time synchronization in a PTP domain. A BC uses one port to synchronize the time with an upstream device and uses the other ports to synchronize the time to downstream devices.

    A clock node is also a BC device if it functions as the clock source and synchronizes the time to downstream devices through multiple PTP ports.

PTP Port

A PTP port is a port running PTP. PTP ports are classified into the following types based on roles:
  • Master port: is located on a BC or OC device and sends synchronization time to a downstream port.
  • Slave port: is located on a BC or OC device and receives synchronization time from an upstream port.
  • Passive port: is an idle port on a BC device and does not receive or send synchronization time.

Master-Slave hierarchy

Nodes in a PTP domain establish the master-slave hierarchy for time synchronization. Master nodes send synchronization time, while slave nodes receive synchronization time. The clock on the master node is the master clock, and the clock on the slave node is the slave clock. The port that sends synchronization time is the master port, and the port that receives synchronization time is the slave port.

A device may receive synchronization time from an upstream node and then send the synchronization time to a downstream node.

Grandmaster Clock

All clock nodes in a PTP domain are organized into the master-slave hierarchy. The grandmaster clock (GMC) is at the top of the hierarchy and is the reference clock in the PTP domain. Clock nodes exchange 1588v2 messages to synchronize the GMC time to the entire PTP domain. Therefore, the GMC is also called the clock source of the PTP domain. The GMC can be statically configured or dynamically elected through the best master clock (BMC) algorithm.

Clock Source Selection

Switches support the following clock source selection modes:
  • Static clock source selection: A specified clock source is selected as the master clock source.
  • BMC algorithm: A 1588v2 device uses the BMC algorithm to dynamically select the best master clock on the network to ensure clock accuracy of devices.

1588v2 defines an Announce message for clock nodes to exchange time source information, such as the grandmaster priority, clock class, time accuracy, and the number of hops to the grandmaster clock. Based on the preceding information, clock nodes select the grandmaster clock, select specific ports to synchronize the time with the grandmaster clock, and determine the master-slave hierarchy. After a clock source is selected, a loop-free meshed tree-shaped network is built and rooted at the grandmaster clock.

The master node periodically sends an Announce message to the slave node. If the slave node does not receive any Announce message from the master node within a certain period, it considers the master-slave hierarchy invalid, selects a clock source again, and uses another port to establish the master-slave hierarchy for time synchronization.

Virtual Clock ID

A virtual clock ID uniquely identifies a 1588v2 device.

Updated: 2019-04-20

Document ID: EDOC1100075362

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