Forward Error Correction

Table 1. Feature History

Feature Name

Release Information

Description

Forward Error Correction

Cisco IOS XE SD-WAN Release 16.11.x

Feature introduced. FEC is a mechanism to recover lost packets on a link by sending extra “parity” packets for every group of 4 packets.

IPv6 support for Forward Error Correction

Cisco IOS XE Catalyst SD-WAN Release 17.15.1a

IPv6 support for Forward Error Correction is added.

Forward Error Correction (FEC) is a mechanism to recover lost packets on a link by sending extra “parity” packets for every group of 4 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. FEC is supported on Cisco IOS XE Catalyst SD-WAN devices.


Note
We recommend Cisco IOS XE Release 17.6.3 as the minimum release when using FEC.

Note
Monitoring FEC through Cisco SD-WAN Manager is not supported.

Supported Traffic

Cisco IOS XE Catalyst SD-WAN Devices support forward error correction for the following traffic types:

From Cisco IOS XE Catalyst SD-WAN Release 16.12.1b:

IPv4 traffic over IPv4 tunnel

From Cisco IOS XE Catalyst SD-WAN Release 17.15.1a:

  • IPv4 traffic over IPv6 tunnel

  • IPv6 traffic over IPv4 tunnel

  • IPv6 traffic over IPv6 tunnel

Supported Devices for Forward Error Correction

The forward error correction is supported on all the Cisco IOS XE Catalyst SD-WAN devices.

Configure Forward Error Correction for a Policy

Procedure

Step 1

From the Cisco SD-WAN Manager menu, choose Configuration > Policies.

Step 2

Click Centralized Policy and then click Add Policy.

Step 3

Click Next.

Step 4

Click Next again and then click Configure Traffic Rules.

Step 5

Click Traffic Data, and from the Add Policy drop-down list, choose Create New.

Step 6

Click Sequence Type.

Step 7

From the Add Data Policy pop-up menu, choose QoS.

Step 8

Click Sequence Rule.

Step 9

In the Applications/Application Family List, choose one or more applications or lists.

Step 10

Click Accept.

Step 11

Click Actions and click Loss Correction.

Step 12

In the Actions area, choose one of the following:

  • FEC Adaptive: Only send FEC information when the loss detected by the system exceeds the packet loss threshold.

  • FEC Always: Always send FEC information with every transmission.

  • Packet Duplication check box: Duplicates packets through secondary links to reduce packet loss if one link goes down.

Step 13

Click Save Match and Actions.

Step 14

Click Save Data Policy.

Step 15

Click Next and take these actions to create a centralized policy:

  1. Enter a Name and a Description.

  2. Select Traffic Data Policy.

  3. Choose VPNs and a site list for the policy.

  4. Save the policy.

Monitor Forward Error Correction Status Using the CLI

Use the show sdwan tunnel statistics fec command to verify the FEC status on a Cisco IOS XE Catalyst SD-WAN device: 

Device# show sdwan tunnel statistics fec 
tunnel stats ipsec 192.0.2.1 203.0.113.1 12346 12366
fec-rx-data-pkts     0
fec-rx-parity-pkts   0
fec-tx-data-pkts     0
fec-tx-parity-pkts   0
fec-reconstruct-pkts 0
fec-capable          true
fec-dynamic          false
tunnel stats ipsec 192.0.2.1 203.0.113.1 12346 12346
fec-rx-data-pkts     122314
fec-rx-parity-pkts   30578
fec-tx-data-pkts     125868
fec-tx-parity-pkts   31467
fec-reconstruct-pkts 3
fec-capable          true
fec-dynamic          false

The following table describes the FEC counters related to the output shown in the show sdwan tunnel statistics fec command:

Name of Counter

Description

fec-rx-data-pkts

Displays the number of data packets received by the device.

fec-rx-parity-pkts

Displays the number of parity packets received by the device.

fec-tx-data-pkts

Displays the number of data packets sent by the device.

fec-tx-parity-pkts

Displays the number of parity packets sent by the device.

fec-reconstruct-pkts

Displays the number of received packets reconstructed by the device.