Packet Duplication

Table 1. Feature History

Feature Name

Release Information

Description

Packet Duplication for Noisy Channels

Cisco IOS XE Catalyst SD-WAN Release 16.12.1b

This feature helps mitigate packet loss over noisy channels, thereby maintaining high application QoE for voice and video.

Packet Duplication for Large Packets Using Underlay Fragmentation

Cisco IOS XE Catalyst SD-WAN Release 17.15.1a

Cisco Catalyst SD-WAN Control Components Release 20.15.1

This feature enables packet duplication even when the packet size is greater than the path maximum transmission unit (PMTU) discovered on the duplicate tunnel. With the help of underlay fragmentation, this feature uses adjacency MTU instead of tunnel PMTU to provide this capability.

Cisco SD-WAN Manager provides a chart for viewing packet duplication information for tunnels.

Information about Packet Duplication

Cisco IOS XE Catalyst SD-WAN devices use packet duplication to overcome packet loss.

Packet duplication sends copies of packets on alternate available paths to reach Cisco IOS XE Catalyst SD-WAN devices. If one of the packets is lost, a copy of the packet is forwarded to the server. Receiving Cisco IOS XE Catalyst SD-WAN devices discard copies of the packet and forward one packet to the server.

Packet duplication is suitable for edges with multiple access links. Once packet duplication is configured and pushed to your device, you can see the tunnel packet duplication statistics.

Packet Duplication for Large Packets Using Underlay Fragmentation

When packets are intercepted for duplication, the system queries the IP database using the incoming tunnel ID. It then fetches the duplicate tunnel object. The system compares the packet length with the path maximum transmission unit (PMTU) of the duplicate tunnel. If the packet length is smaller than the duplicate tunnel's PMTU, the packets are duplicated.

Starting from Cisco IOS XE Catalyst SD-WAN Release 17.15.1a, packet duplication with underlay fragmentation ensures that packets get duplicated even when the packet size is more than the PMTU of duplicate tunnel.

For more information on how to enable underlay fragmentation, see VFR and Underlay Fragmentation.

To monitor packet duplication statistics, see View Loss Percentage, Latency, Jitter, Octet, and Packet Duplication Information for Tunnels.

Supported Traffic

Cisco IOS XE Catalyst SD-WAN Devices support packet duplication 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

Configure Packet Duplication Using Centralized Policy

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

  2. Select Centralized Policy at the top of the page and then click Add Policy.

  3. Click Next twice to select Configure Traffic Rules.

  4. Select Traffic Data, and from the Add Policy drop-down list, click Create New.

  5. Click Sequence Type in the left pane.

  6. From the Add Data Policy pop-up window, select QoS.

  7. Click Sequence Rule.

  8. In the Applications/Application Family List/Data Prefix, select one or more applications or lists.

  9. Click Actions and choose Loss Correction.

  10. In the Actions area, select the Packet Duplication option to enable the packet duplication feature.

    • FEC Adaptive: Only send Forward Error Correction (FEC) information when the system detects a packet loss.

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

    • None: Use when no loss protection is needed.

    • Packet Duplication: Enable when packets need to be duplicated and sent on the next available links to reduce packet loss.

  11. Click Save Match and Actions.

  12. Click Save Data Policy.

  13. 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/site list for the policy.

    4. Save the policy.

Configure Packet Duplication Using Policy Groups

Minimum supported release: Cisco Catalyst SD-WAN Control Components Release 20.14.1

  1. Select Configuration > Policy Groups.

  2. Click Application Priority & SLA.

  3. Click Add Application Priority & SLA Policy. Provide a policy name and description.

  4. Enable Advanced Layout in the top right pane.

  5. Click Add Traffic Policy.

  6. Enter a name for the policy and specify VPNs.

  7. In the Direction drop-down list, select All.

  8. In the Default Action, click Accept.

  9. Click Add.

  10. Click Add Rules.

  11. Click Match. Select appropriate match condition.

  12. Click Action > Loss Correction.

  13. In the Type drop-down list, choose Packet Duplication

  14. Click Save Match and Actions.

  15. Click Save Policy.

Configure Underlay Fragmentation Using Cisco SD-WAN Manager

Minimum supported releases: Cisco IOS XE Catalyst SD-WAN Release 17.15.1a

  1. From the Cisco SD-WAN menu, choose Configuration > Configuration Groups.

  2. Click Transport & Management Profile.

  3. Select the desired transport profile and click Edit.

  4. Click Edit Ethernet Interface > Tunnel.

  5. Enable Allow Fragmentation and MTU To Max.

  6. Click Save.

Restrictions for Packet Duplication

  • Packet duplication interop, forward error correction (FEC), and TCP optimization on Cisco IOS XE Catalyst SD-WAN devices is not supported between Cisco IOS XE Release 16.x and Cisco IOS XE Catalyst SD-WAN Release 17.x versions.

  • Packet duplication cannot work in conjunction with local or remote TLOC in the policy. Data policy or AAR is not configured when specifying the packet duplicated tunnel.

Monitor Packet Duplication Statistics for a Device

  1. From the Cisco SD-WAN Manager menu, choose Monitor > Devices.

  2. Choose a device.

  3. For a device, in the Action column, click ... and choose Real Time.

  4. In the Device Options drop-down menu, click Tunnel Packet Duplication Statistics.

Monitor Tunnel Information for a Device

  1. From the Cisco SD-WAN Manager menu, choose Monitor > Devices.

  2. Click a device name.

  3. In the left pane, click Tunnel in the WAN area.

    The right pane displays information about tunnel connection information, including loss percentage, latency, jitter, octets, and packet duplication.

  4. In the right pane, click Chart Options to choose the format in which you want to view the information.