Enabling Forward Error Correction

The Forward Error Correction (FEC) functionality reduces the loss of traffic packets in links, especially for UDP applications, and the number of retransmissions, which lead to delays, and also recovers received data on the CPE device. Data recovery is provided by redundant encoding of the data stream on the device on the sending side.

We recommend using FEC on noisy links to reduce the packet loss and increase the speed of TCP connections.

The sender CPE encodes the stream of traffic packets egressing into the tunnel, adding redundant packets. The use of encoding on the sending and receiving sides may cause delays due to extra data processing. You can configure the degree of redundancy in the settings of the SD-WAN Controller or when you enable FEC.

The receiving CPE device buffers traffic packets received through the tunnel and decodes them, recovering lost packets, if possible. The general diagram of FEC is shown in the figure below.

FEC diagram

You can enable FEC 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 FEC on a tunnel, use the following instructions:

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

  To enable FEC 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 FEC/reordering.
  5. This opens a window; in that window, select the Override check box to configure FEC on the tunnel.
  6. In the Redundancy ratio (original/redundant packet) drop-down list, select the degree of redundancy of transmitted traffic packets, which is the ratio between the original packets and extra packets containing redundant code. The default setting is 0:0 FEC off and the functionality is not active.
  7. In the Timeout field, enter the maximum time, in milliseconds, during which a traffic packet can stay in the queue for FEC to apply. Range of values: 1 to 1000.
  8. Click Save.
• Enabling FEC on a tunnel using the graphical topology.

  To enable FEC 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 FEC/reordering.
  5. This opens a window; in that window, select the Override check box to configure FEC on the tunnel.
  6. In the Redundancy ratio (original/redundant packet) drop-down list, select the degree of redundancy of transmitted traffic packets, which is the ratio between the original packets and extra packets containing redundant code. The default setting is 0:0 FEC off and the functionality is not active.
  7. In the Timeout field, enter the maximum time, in milliseconds, during which a traffic packet can stay in the queue for FEC to apply. Range of values: 1 to 1000.
  8. Click Save.
• Enabling FEC 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 FEC/reordering.
  5. This opens a window; in that window, select the Override check box to configure FEC on the tunnel.
  6. In the Redundancy ratio (original/redundant packet) drop-down list, select the degree of redundancy of transmitted traffic packets, which is the ratio between the original packets and extra packets containing redundant code. The default setting is 0:0 FEC off and the functionality is not active.
  7. In the Timeout field, enter the maximum time, in milliseconds, during which a traffic packet can stay in the queue for FEC to apply. Range of values: 1 to 1000.
  8. Click Save.
  9. In the upper part of the settings area, click Save to save CPE device settings.