Enabling Dampening

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Dampening is a configurable mechanism that prevents the use of tunnels that change state too frequently. When determining instability, the following state changes are taken into account:

• UP/LIVE → DOWN/NOT-LIVE.
• DOWN/NOT-LIVE → UP/LIVE.
• UP/LIVE → UP/NOT-LIVE.
• UP/NOT-LIVE → UP/LIVE.

The LIVE and NOT-LIVE states are used to integrate the Dampening function with the Ethernet Connectivity Fault Management (CFM) protocol, which detects the loss of two-way Ethernet connectivity of the segment between peer switches without the service interface entering the DOWN state (Rx signal loss).

Dampening is applied to both ends of the Ethernet segment.

This functionality does the following within a deployed SD-WAN network:

• Detect frequent changes of the states of service interfaces.
• Move transport services suffering from instability of service interfaces to backup tunnels.
• Exclude segments tied to the service interfaces from route calculation for transport services.

When the Dampening functionality is enabled, each state change of the service interface through which the tunnel is constructed increases the Penalty value. If the Penalty factor reaches the threshold value within a certain period of time, access to the tunnel is restricted (its cost is increased 10,000 times for a certain period of time). The value of each of these parameters is specified when you enable the feature. By default, access to the tunnel is resumed if the state of the service interface does not change for 10 minutes.

You can enable Dampening on an individual tunnel. The tunnels are displayed in a common table in the Tunnels section; in the graphical topology in the Topology section; and in the CPE device configuration on the Tunnels tab. Only tunnels built using the particular CPE device are displayed in the configuration of that device.

To enable Dampening on a tunnel, use the following instructions:

• Enabling Dampening on a tunnel using the overall table of tunnels.

  To enable Dampening on a tunnel using the overall table of tunnels:

  1. In the menu, go to the Infrastructure section.

     This opens the resource management page. By default, the Network resources tab is selected, which displays the table of SD-WAN and SDN Controllers.

  2. Click Management → Configuration menu next to the SD-WAN Controller.

     This opens the Controller configuration menu. By default, you are taken to the Controller nodes section, which displays a table of Controller nodes.

  3. Go to the Tunnels section.

     A table of tunnels is displayed.

  4. Click Management next to the tunnel and in the drop-down list, select Dampening.
  5. This opens a window, in that window, select the Enable check box.
  6. In the Maximum suppress time (ms.) field, enter the maximum length of time, in milliseconds, for which access to the tunnel can be restricted. When the specified time elapses, all Dampening counters on the tunnel are reset. The default setting is 600,000.
  7. In the Penalty, enter the number by which Penalty is incremented when the tunnel changes state. The default setting is 1.
  8. In the Suppress threshold field, enter the Penalty value at which access to the tunnel is restricted. The default setting is 4.
  9. In the Update interval (ms.) field, enter the time in milliseconds during which Penalty must attain the value specified in the Suppress threshold field for access to the tunnel to be restricted. The default setting is 120,000.
  10. To view Dampening statistics for a tunnel, click Load statistics.
  11. Click Save.
• Enabling Dampening on a tunnel using the graphical topology.

  To enable Dampening on a tunnel using the graphical topology:

  1. In the menu, go to the Infrastructure section.

     This opens the resource management page. By default, the Network resources tab is selected, which displays the table of SD-WAN and SDN Controllers.

  2. Click Management → Configuration menu next to the SD-WAN Controller.

     This opens the Controller configuration menu. By default, you are taken to the Controller nodes section, which displays a table of Controller nodes.

  3. Go to the Topology section.

     The SD-WAN topology is displayed.

  4. Click the tunnel to open a window and in that window, click Dampening.
  5. This opens a window, in that window, select the Enable check box.
  6. In the Maximum suppress time (ms.) field, enter the maximum length of time, in milliseconds, for which access to the tunnel can be restricted. When the specified time elapses, all Dampening counters on the tunnel are reset. The default setting is 600,000.
  7. In the Penalty, enter the number by which Penalty is incremented when the tunnel changes state. The default setting is 1.
  8. In the Suppress threshold field, enter the Penalty value at which access to the tunnel is restricted. The default setting is 4.
  9. In the Update interval (ms.) field, enter the time in milliseconds during which Penalty must attain the value specified in the Suppress threshold field for access to the tunnel to be restricted. The default setting is 120,000.
  10. To view Dampening statistics for a tunnel, click Load statistics.
  11. Click Save.
• Enabling Dampening on a tunnel in the configuration of an individual CPE device.

  To enable Dampening on a tunnel in the configuration of a CPE device:

  1. In the menu, go to the SD-WAN → CPE section.

     A table of CPE devices is displayed.

  2. Click the CPE device.

     The settings area is displayed in the lower part of the page. You can expand the settings area to fill the entire page by clicking the expand icon . By default, the Configuration tab is selected, which displays the current configuration of the CPE device. This tab also displays the table of Out-of-band management CPE device configurations.

  3. Select the Tunnels tab.

     A table of tunnels is displayed.

  4. Click Management next to the tunnel and in the drop-down list, select Dampening.
  5. This opens a window, in that window, select the Enable check box.
  6. In the Maximum suppress time (ms.) field, enter the maximum length of time, in milliseconds, for which access to the tunnel can be restricted. When the specified time elapses, all Dampening counters on the tunnel are reset. The default setting is 600,000.
  7. In the Penalty, enter the number by which Penalty is incremented when the tunnel changes state. The default setting is 1.
  8. In the Suppress threshold field, enter the Penalty value at which access to the tunnel is restricted. The default setting is 4.
  9. In the Update interval (ms.) field, enter the time in milliseconds during which Penalty must attain the value specified in the Suppress threshold field for access to the tunnel to be restricted. The default setting is 120,000.
  10. To view Dampening statistics for a tunnel, click Load statistics.
  11. Click Save.
  12. In the upper part of the settings area, click Save to save CPE device settings.