High Availability:Hardware:Clocking

The clock is a necessary component of a TDM network. Synchronizing your system on the right clock, allows it to perform properly.

Clock Sources

The Toolpack system can synchronize the system on 3 types of sources:

• BITS port (Available on TMG7800 telecom units and TMG7800 telecom units with DS3 or SONET/SDH mezzanine. Also available on the 7800 TMS )
• Line Service
• SONET/SDH interface

Choosing Clock Reference

Always place the most reliable clock source at the top of the clock references list in the web portal. This will avoid unnecessary clock switch over. TelcoBridges recommend to synchronize the clock on the BITS port when available. If your system includes 7800 TMS, it is recommended that you use the 7800 TMS BITS ports as clock sources.

When the system selects a clock, it will only use clock sources that are valid and that are available on an active device of the system. For example, in a system containing two 7800 TMS ( one will be active, the other standby ) the clock sources on the standby 7800 TMS (BITS ports) will not be selected. In the figure below, the clock source #3 and #4 will not be selected as system clock unless the standby 7800 TMS becomes active.

Clock Redundancy

The system clock is configured using the Toolpack web portal. Toolpack allows the system to have a system clock references list. Clock redundancy is accomplished by configuring at least 2 valid clock references in the system. The system will scan through the clock references list until it finds a valid one. If the active clock source becomes unavailable, the system will scan through the clock reference list again to find another valid clock source. Clock recovery, which means that the system will switch back to a more preferred clock source if it becomes available again, can be configured in TMS network.

Another redundancy feature for the system clock are the two BITS ports that can be assigned to different clock source.

Recommended Setup

Here is an example of a system clock where 2 7800 TMS and the system have selected clock source #1 as system clock:

References

NOTE:These references assume that your system is running at the very minimum on Toolpack v2.3. To configure the system, please select the appropriate Toolpack Web Tutorial Guide.