Configure a Synchronization Priority List
- Kelli Higdon
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Before connecting to a network the IMG 2020 must be synchronized to a T1/E1 timing source such as a T1 or E1 span. The IMG 2020 will allow up to six different clock sources to be connected to various inputs on the rear of the unit. In the Web GUI an object labeled Timing Synchronization Priority List can be configured. The Timing Synchronization Priority List will allow the IMG 2020 to set a priority on which clock source will get highest priority and which clock source will get lowest priority. For example, the default Timing Synchronization Priority List is configured so the IMG 2020 first determines if the Primary Reference Clock Port has a loop timing source on it. If it is does not, it determines if the Secondary Reference Clock Port has a loop timing source on it. The IMG 2020 continues to check each port in succession until it finds an available timing source.Â
Procedure
Prior to configuring the Timing Synchronization Priority List configure the physical node must be configured.
Primary and Secondary Reference Timing are hard-coded and are automatically configured. If Primary Loop and/or Secondary Loop Timing is going to be used, you must first configure the Primary and/or Secondary Loop timing source to a DS-1. This can be configured on any DS-1 accept the DS-1's with the Primary and Secondary Timing hard coded to them. To configure, select the DS-1 Spans object.
In the Object Table at the bottom of the DS-1 Spans object, double click on one of the DS-1's in the list. This will open up a Span specification pane. Select Set Primary from drop down menu of the Loop Timing field.
Repeat steps 2 and 3 to configure the Secondary Loop Timing source. Select Set Secondary.
Right click the IMG 2020 object and select New Timing Synchronization Priority List. The Timing Synchronization Priority List pane appears as displayed below
The priority in which the IMG 2020 will use the timing ports is configured here. The priority is displayed from top to bottom. The top most entry gets the highest or first priority and then the priority decreases as you move to the bottom. The priority can be changed by moving the entries up or down in the list. Highlight which entry to move and select the Up or Down arrow button and the entry will move accordingly. Refer to screen capture below.
Moves highlighted entry up or down one space at a time
Moves highlighted entry from existing position to either the top or bottom space.
Only the first five selections in the Timing List will be used. The last two timing sources in the list are ignored. The Priority List in the example above consists of Primary Reference, Secondary Reference, Primary Loop, Secondary Loop, Free Running, Optical Working, and Optical Protection. The Free Running clock source needs to be one of the first five clock sources in the list. If the Free Running clock source is in position six or seven of the list, an error will occur and not allow the list to be sent to the IMG 2020.
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Below is an explanation of each of the timing references and how they are used:
Clock Source | Description |
Primary Reference | Primary Reference is hard-coded to the DS-1 within interface 0. This interface is one of four interfaces that are labeled T1/E1. The timing source does not need to be configured. Connect a DS-1 to this interface and the IMG 2020 will automatically synchronize with the T1 or E1 loop timing source. The Primary Reference Timing selection can be moved up or down the priority list as desired |
Secondary Reference | Secondary Reference is hard-coded to the DS-1 within the interface 1. This interface is one of four interfaces that are labeled T1/E1. The timing source does not need to be configured. Connect a DS-1 to this interface and the IMG 2020 will automatically synchronize with the T1 or E1 loop timing source. The Secondary Reference Timing selection can be moved up or down the priority list as desired |
Primary Loop | Primary Loop timing can be configured on any DS-1 other than the DS-1's used for Primary and Secondary Reference timing described above. To configure, highlight the DS-1 Spans object. In the Object Table at bottom of pane, double click on one of the DS-1's and this will open up a Span Specification pane. Select Set Primary from the drop down menu of the Loop Timing field. Once the timing source is set, the Primary Loop selection in the Timing Synchronization Priority List can be moved up or down the priority list as desired. |
Secondary Loop | Secondary Loop timing can be configured on any DS-1 other than the DS-1's used for Primary and Secondary Reference timing described above. To configure, highlight the DS-1 Spans object. In the Object Table at bottom of pane, double click on one of the DS-1's and this will open up a Span Specification pane. Select Set Secondary from the drop down menu of the Loop Timing field. Once the timing source is set, the Secondary Loop selection in the Timing Synchronization Priority List can be moved up or down the priority list as desired. |
Free Running | The Free Running source is the clock source generated internally. It is not recommended that the Free Running source be used as an external clock source used to time the network. The Free Running source is used as a backup source in the event all network timing sources have failed. The Free running timing source should always be configured as one of the top 5 clock sources in the Timing Synchronization Priority List. Preferably, the Free Running timing source should always be set to the 5th position in this list. |
Optical Working | The timing source labeled Optical Working is configured on the optical interface labeled W on the rear of the IMG 2020. Timing in this case is automatically synced to the optical streams of the Working interface. When optical Working is being used to sync to a timing source, move the Optical Working selection to the topmost position of the list. Not supported on the 24 Port I/O.  When the optical interface is being utilized, the optical working and optical protection timing sources must be configured as the first and second timing sources in the Timing Synchronization Priority List. |
Optical Protection | The timing source labeled Optical Protection is the redundant optical interface and is configured on the optical interface labeled P on the rear of the IMG 2020. Timing in this case is automatically synced to the optical streams of the Protection interface. When optical Protection is being used to sync to a timing source, move the Optical Protection selection to the second position of the list. Not supported on the 24 Port I/O.  When the optical interface is being utilized, the optical working and optical protection timing sources must be configured as the first and second timing sources in the Timing Synchronization Priority List. |
Additional Information
The Primary Reference sync is hard-coded so that interface 0 of the T1/E1 interfaces on the rear of the IMG 2020 will always be designated as Primary Reference.
The Secondary Reference sync is hard-coded so that interface 1 of the T1/E1 interfaces on the rear of the IMG 2020 will always be designated as Secondary Reference.
Any of the other Bearer Interfaces (Optical or DS3) and/or the RJ48 T1/E1 interfaces 2 or 3 on the rear of the IMG 2020 can designated as a Primary Loop or Secondary Loop timing sync reference.
For more information, refer to the Configure Network Timing and Timing Synchronization Priority List topics.