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Viptela Documentation

Forward Error Correction

Forward Error Correction is a mechanism to recover lost packets on a link by sending extra “parity” packets for every group (N) of packets. As long as the receiver receives a subset of packets in the group (at-least N-1) and the parity packet, up to a single lost packet in the group can be recovered.

Configure FEC

To configure FEC, follow these steps:

  1. Select Configuration Policies.
  2. Select Centralized Policy.
  3. Select Centralized Policy at the top of the page and then click Add Policy.
  4. Click Next twice to select Configure Traffic Rules.
  5. Select Traffic Data, and the from the Add Policy drop-down menu, select click Create New.
  6. Click Sequence Type in the left panel.
  7. From the Add Data Policy pop-up menu, select QoS.
  8. Click Sequence Rule.
  9. Click Applications/Application Family List/Data Prefix.
  10. Select one or more applications or lists.
  11. Click Actions and select Loss Correction.
  12. In the Actions area, select one of the following:
  • FEC Adaptive—Only send FEC information only when the system detects packet loss
  • FEC Always—Always send FEC information with every transmission
  1. Click Save Match and Actions.
  2. Click Save Data Policy.
  3. Click Next and take these actions to create a Centralized Policy:
  1. Enter a Name and Description.
  2. Select Traffic Data Policy.
  3. Choose VPNs/site list for the policy.
  4. Save the policy.

Monitor FEC

To monitor FEC tunnel information, follow these steps:

  1. Select Monitor Network.
  2. Select a device group.
  3. In the left panel, click Tunnel, which displays under WAN.

The WAN tunnel information includes the following:

  • A graph that shows the total tunnel loss for the selected tunnels.
  • A graph that shows the FEC loss recovery rate for the selected tunnels. The system calculates this rate by dividing the total number of reconstructed packets by the total number of lost FEC-enabled packets.
  • A table that provides the following for each tunnel endpoint:
  • Name of the tunnel endpoint
  • Communications protocol that the endpoint uses
  • State of the endpoint
  • Jitter, in ms, on the endpoint
  • Packet loss percentage for the endpoint
  • FEC loss recovery percentage for the endpoint
  • Latency, in ms, on the endpoint
  • Total bytes transmitted from the endpoint
  • Total bytes received by the endpoint
  • Application usage link

To monitor FEC application family information, follow these steps:

  1. Select Monitor Network.
  2. Select a device group.
  3. In the left panel, click DPI, which displays under Application.

The FEC application information includes the following:

  • A graph for which you can select any of the following perspectives:
  • Application Usage—Usage of various types of traffic for the selected application families, in KB.
  • Application Goodput—Goodput metadata for the selected application families.
  • Mean Opinion Score (MOS)—MOS for the selected application families.
  • FEC Recovery Rate— FEC loss recovery rate for the selected application families. The system calculates this rate by dividing the total number of reconstructed packets by the total number of lost FEC-enabled packets.
  • A table that provides the following for each application family:
  • Name of the application family
  • Goodput, in kbps, for the application family
  • MOS for the selected application family
  • FEC loss recovery percentage for the application family
  • Traffic usage, in MB, for the selected application family
  • Percentage of total traffic used by the application family

 

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