Enabling Dampening

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Dampening is a configurable mechanism that prevents the use of links 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 neighbor 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 links.
• 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 link is constructed increases the Penalty value. If the Penalty factor reaches the threshold value within a certain period of time, access to the link 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 link is resumed if the state of the service interface does not change for 10 minutes.

You can enable Dampening on an individual link. All links built within the SD-WAN network are displayed in the overall table of links in the Tunnels section, as well as in the graphic topology in the Topology section. A table of links built using a particular CPE device is also displayed in the configuration of that CPE device, on the Tunnels tab.

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

• Enabling Dampening on a link using the overall table of links.

  To enable Dampening on a link using the overall table of links:

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

     The SD-WAN infrastructure management page is displayed. By default, the Network resources tab is selected, which displays the table of SD-WAN Controllers.

  2. Click Management next to the SD-WAN Controller and in the drop-down list, select Configuration menu.

     This opens the SD-WAN 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 links is displayed.

  4. Click Management next to the link 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 link can be restricted. When the specified time elapses, all Dampening counters on the link are reset. The default setting is 600,000.
  7. In the Penalty, enter the number by which Penalty is incremented when the link changes state. The default setting is 1.
  8. In the Suppress threshold field, enter the Penalty value at which access to the link 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 link to be restricted. The default setting is 120,000.
  10. To view Dampening statistics for a link, click Load statistics.
  11. Click Save.
• Enabling Dampening on a link using the graphical topology.

  To enable Dampening on a link using the graphical topology:

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

     The SD-WAN infrastructure management page is displayed. By default, the Network resources tab is selected, which displays the table of SD-WAN Controllers.

  2. Click Management next to the SD-WAN Controller and in the drop-down list, select Configuration menu.

     This opens the SD-WAN 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 link 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 link can be restricted. When the specified time elapses, all Dampening counters on the link are reset. The default setting is 600,000.
  7. In the Penalty, enter the number by which Penalty is incremented when the link changes state. The default setting is 1.
  8. In the Suppress threshold field, enter the Penalty value at which access to the link 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 link to be restricted. The default setting is 120,000.
  10. To view Dampening statistics for a link, click Load statistics.
  11. Click Save.
• Enabling Dampening on a link in the configuration of an individual CPE device.

  To enable Dampening on a link on an individual CPE device:

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

     By default, the CPE subsection is displayed with a table of CPE devices.

  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 button .

  3. Select the Tunnels tab.

     A table of links is displayed.

  4. Click Management next to the link 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 link can be restricted. When the specified time elapses, all Dampening counters on the link are reset. The default setting is 600,000.
  7. In the Penalty, enter the number by which Penalty is incremented when the link changes state. The default setting is 1.
  8. In the Suppress threshold field, enter the Penalty value at which access to the link 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 link to be restricted. The default setting is 120,000.
  10. To view Dampening statistics for a link, click Load statistics.
  11. Click Save.
  12. In the upper part of the settings area, click Save to save the configuration of the CPE device.