Configuring Dynamic 1588v2 Functions

On a 1588v2 network, the best master clock algorithm (BMCA) is typically used to dynamically determine a master clock. 1588v2 functions need to be configured according to the device type.

Usage Scenario

A 1588v2 network has to import BITS time signals before implementing clock synchronization. The BMC algorithm can be used to select the grandmaster and determine the master and slave clocks. A dynamic 1588v2 network allows devices to elect a clock source with the highest priority.

Typical dynamic 1588v2 network with OC, BC, TC, and TCOC devices

Figure 1 shows that a BC and an OC are separately connected to BITSs or GPSs. The BC and OC use the BMC algorithm to select the OC as the grandmaster. The grandmaster obtains time signals and sends 1588v2 packets carrying time information over the bearer network. TCs, including the TCOC, are core devices on the bearer network. TCs transparently transmit time information over the bearer network. The TCOC can also implement frequency synchronization. BCs at the edge of the bearer network send highly accurate time information carried in 1588v2 packets to wireless access devices, such as NodeBs and radio network controllers (RNCs).

Figure 1 Dynamic 1588v2 application
Typical dynamic 1588v2 network with TCandBC devices

All devices, including the NodeB, run 1588v2 on the network shown in Figure 2. ISP A operates the NodeB, OC2, and to the BC. OC2 is connected to BITS2, and to the BC is connected to a BITS or GPS. ISP A's network does not have bearer network devices. ISP A leases the bearer network that ISP B operates, and ISP B devices trace BITS1. Time synchronization on ISP A's network is independent of that on ISP B's network. Devices on ISP A's network can dynamically select a clock source. The deployment is as follows:
- Establish domain1 for ISP B's 1588v2 network and domain2 for ISP A's 1588v2 network.
- OC1 in domain1 obtains BITS1 signals and sends 1588v2 packets carrying clock synchronization information to the BC interface that directly connects the TCandBC to OC1.
- OC2 in domain2 obtains signals from the grandmaster and sends 1588v2 packets carrying clock synchronization information to the TCandBC. TC interfaces connect the TCandBC to OC2 and to the BC. The TC interfaces transparently transmit BITS2 time information to the BC. Upon receipt, the BC advertises the time information to the NodeB.
Figure 2 Typical dynamic 1588v2 network with TCandBC devices

Pre-configuration Tasks

Set physical parameters of interfaces and ensure that the interfaces are physically Up.
The license file on the main control board has been activated by running the license active file-name command. When the clock synchronization license is not loaded, the ptp enable configuration is not allowed.

Importing Time Signals from an External BITS Source: On a 1588v2 network, time signals are typically imported from an external BITS source. You can configure multiple routers to import time signals from an external BITS source. A master clock can be selected dynamically or statically.

Configuring Clock Source Attributes for BMC Selection: This section describes how to configure clock source attributes used for BMC selection. The routers configured with clock source attributes can participate in BMC selection. A local clock on a 1588v2 router can also participate in BMC selection. The BMC algorithm helps 1588v2 routers to select a master clock. The master clock provides time signals for other routers over a 1588v2 network. 1588v2 routers obtain clock synchronization information from the grandmaster.

Globally Enabling 1588v2: 1588v2 takes effect after you configure 1588v2 in both the system and interface views. After 1588v2 is enabled in the system view, you also need to set other basic information, including the domain number and virtual clock ID, to establish a 1588v2 network.

(Optional) Enabling the Control of Access to 1588v2 Clock Sources: This section describes how to enable a 1588v2 router to control the access to clock sources. A 1588v2 network contains lots of routers that participate in dynamic clock source selection. Clock source-based attacks or configuration errors cause clock flapping over the 1588v2 network. You can enable the control of the access to clock sources so that a 1588v2 router selects a clock source within a specified range.

(Optional) Monitoring the Performance of a Passive Interface: This section describes how to monitor the performance of a passive interface. After a 1588v2 network achieves stable time synchronization, monitor the passive interface's offset that is between the master and slave clocks.

Enabling 1588v2 on a Specific Interface: This section describes how to enable 1588v2 on a specific interface. 1588v2 takes effect after you configure 1588v2 in the system and interface views. You can set 1588v2 parameters in the interface view. The parameters include the link delay measurement mechanism, asymmetric delay correction, and timestamping mode.

(Optional) Configuring Time Attributes for 1588v2 Packets: This section describes how to configure time attributes for 1588v2 packets. 1588v2 routers exchange Announce, Sync, and Delay or Pdelay packets to send time information and maintain 1588v2 connections. You can set the interval at which a 1588v2 interface sends Announce, Sync, and Delay or Pdelay packets and the maximum number of Announce packet timeouts. Using the default time attribute values is recommended.

(Optional) Configuring a 1588v2 Packet Encapsulation Mode: 1588v2 packets can be encapsulated into Layer 2 or Layer 3 packets. You can configure an encapsulation mode for 1588v2 packets based on the actual network conditions, as well as the destination addresses and transmission priority for the 1588v2 packets.

Verifying the Configuration of Dynamic 1588v2 Functions: After configuring dynamic 1588v2 functions, verify the configuration.