Enabling Forward Error Correction

The Forward Error Correction (FEC) functionality reduces the loss of traffic packets in communication channels, 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 link, 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 link 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 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 FEC on a link, use the following instructions:

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

  To enable FEC 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 FEC/reordering.
  5. This opens a window; in that window, select the Override check box to configure FEC on the link.
  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 link using the graphical topology.

  To enable FEC 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 FEC/reordering.
  5. This opens a window; in that window, select the Override check box to configure FEC on the link.
  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 link in the configuration of an individual CPE device.

  To enable FEC on a link in the configuration of 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 FEC/reordering.
  5. This opens a window; in that window, select the Override check box to configure FEC on the link.
  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 the configuration of the CPE device.