Packet Duplication

Feature history for packet duplication

This reference provides feature history information for packet duplication functionality, showing the evolution of capabilities across different software releases.

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.

IPv6 support for Packet Duplication is also added.

Packet duplication on more than one additional tunnel

Cisco IOS XE Catalyst SD-WAN Release 26.1.1

This feature allows you to generate multiple copies for each original packet on more than one additional tunnels.

Packet duplication

Packet duplication is a network feature that

  • duplicates packets on alternate available SD-WAN tunnels to mitigate packet loss

  • enables receiving Cisco IOS XE Catalyst SD-WAN devices to forward one packet to the server and discard the duplicate packets, and

  • is suitable for edges with multiple WAN links.

Packet duplication capabilities

You can view the tunnel packet duplication statistics using device CLI or the Cisco SD-WAN Manager device dashboard.


Note

From Cisco IOS XE Catalyst SD-WAN Release 17.18.1a, the tunnel selection algorithm has been optimized. While selecting a duplicate tunnel, the highest preference is given to the tunnel which has a different local color compared to that of the primary tunnel.

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.

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 these 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

Use one of these methods to configure packet duplication:

Configure packet duplication using policy groups

Configure packet duplication through policy groups to enhance network reliability by creating duplicate packets for critical traffic flows.

Packet duplication is a loss correction technique that sends duplicate copies of packets across different paths to ensure reliable delivery of critical network traffic. This feature is available starting from Cisco Catalyst SD-WAN Control Components Release 20.14.1.

Procedure

Step 1

Select Configuration > Policy Groups.

Step 2

Click Application Priority & SLA.

Step 3

Click Add Application Priority & SLA Policy.

Provide a policy name and description.

Step 4

Enable Advanced Layout in the top right pane.

Step 5

Click Add Traffic Policy.

Step 6

Enter a name for the policy and specify VPNs.

Step 7

In the Direction drop-down list, select All.

Step 8

In the Default Action, click Accept.

Step 9

Click Add.

Step 10

Click Add Rules.

Step 11

Click Match.

Select appropriate match condition.

Step 12

Click Action > Loss Correction.

Step 13

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

Step 14

Click Save Match and Actions.

Step 15

Click Save Policy.

The packet duplication policy is configured and applied to the specified traffic flows, providing loss correction through duplicate packet transmission.

Configure packet duplication on additional tunnels using the CLI

When packet duplication is enabled, by default, packets are duplicated on one additional tunnel. Using the packet-duplication max-preselect<2-4> command, you can enable duplication on 2-4 additional tunnels.

Before you begin

If you do not configure this command, the duplication factor remains 1 by default.

This configuration only configures the duplication number. The actual duplication is enabled using the policy configuration method.

Procedure

Configure the duplication number.

Example:

config-tr
    sdwan
     packet-duplication max-preselect <2-4>

Configure packet duplication using classic policies

Configure packet duplication to reduce packet loss by duplicating packets and sending them on the next available links.

Use classic policies to configure packet duplication for applications that require enhanced reliability and reduced packet loss. This feature is configured through centralized policies in Cisco SD-WAN Manager.

Procedure

Step 1

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

Step 2

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

Step 3

Click Next twice to select Configure Traffic Rules.

Step 4

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

Step 5

Click Sequence Type in the left pane.

Step 6

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

Step 7

Click Sequence Rule.

Step 8

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

Step 9

Click Actions and choose Loss Correction.

Step 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.

Step 11

Click Save Match and Actions.

Step 12

Click Save Data Policy.

Step 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.

The packet duplication policy is configured and applied to the selected applications and VPNs. Packets for the specified applications will be duplicated and transmitted over multiple links to reduce packet loss.

Configure underlay fragmentation using configuration groups

Configure underlay fragmentation to optimize data transmission across network interfaces by enabling fragmentation and MTU settings through configuration groups.

Underlay fragmentation configuration is necessary when network interfaces need to handle data packets that exceed the maximum transmission unit (MTU) size. This task applies to environments where network optimization is required for efficient data flow.

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

Before you begin

Follow these steps to configure underlay fragmentation using configuration groups:

Procedure

Step 1

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

Step 2

Click Transport & Management Profile.

Step 3

Select the desired transport profile and click Edit.

Step 4

Click Edit Ethernet Interface > Tunnel.

Step 5

Enable Allow Fragmentation and MTU To Max.

Step 6

Click Save.

The underlay fragmentation configuration is now enabled for the selected transport profile, allowing the system to handle packet fragmentation and optimize MTU settings for improved network performance.

Restrictions for packet duplication

Consider these restrictions when implementing packet duplication:

  • Packet duplication interop along with 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.

  • Packet duplication is supported only on Cisco IOS XE Catalyst SD-WAN devices but not on all the edge devices.

Monitor packet duplication statistics for a device using the CLI

This reference shows sample output from the show sdwan tunnel statistics pkt-dup command. 

Device#show sdwan tunnel statistics pkt-dup
tunnel stats ipsec 192.0.2.1 203.0.113.1 12366 12406
pktdup-rx                           1313388
pktdup-rx-other                     526666
pktdup-rx-this                      1324958
pktdup-rx-fwd                       540190
pktdup-rx-fwd-dup-tun               789569
pktdup-tx                           0
pktup-tx-other                      0
pktdup-tx-dup-tun-selection-failed  0
pktdup-tx-dup-tun-sent-failed       0
pktdup-capable                      true
pktdup-tx-intercepted              0
pktdup-max-preselect               4

Monitor packet duplication statistics for a device using Cisco SD-WAN Manager

This task enables you to view and analyze packet duplication counters for tunnel traffic on a specific device, helping you monitor network performance and troubleshoot connectivity issues.

Packet duplication statistics provide insights into tunnel packet handling, including original packets received, duplicate packets processed, and failed duplication attempts. These metrics are essential for monitoring network redundancy and tunnel performance.

Procedure

Step 1

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

Step 2

Choose a device.

Step 3

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

Step 4

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

The following table describes the packet duplication counters that appear in the Tunnel Packet Duplication Statistics pane:

Name of Counter

Description

pktdup-rx

Displays number of original packets received by primary tunnel.

pktdup-rx-other

Displays the number of duplicate packets received by this duplicate tunnel.

pktdup-rx-this

N/A

pktdup-rx-fwd

Displays the number of packets received and forwarded by this tunnel.

pktdup-rx-fwd-dup-tun

Displays the number of packets received and forwarded by the duplicate tunnel(s).

pktdup-tx

Displays the total number of duplicate packets generated with respect to this tunnel traffic which will be sent out on duplicate tunnel(s).

pktdup-tx-other

Displays the total number of duplicate packets sent out by this tunnel, but these packets belongs to some other original tunnel.

pktdup-tx-dup-tun-selection-failed

Displays the total number of failed duplication because duplicate tunnels are not available.

pktdup-tx-dup-tun-sent-failed

Displays the total number of duplicated packets failed to be sent out by duplicate tunnel(s).

pktdup-tx-intercepted

Displays the total number of packets which need to be duplicated with respect to this tunnel (equivalent to policy-match).

pktdup-capable

Indicates that this tunnel is capable of supporting the packet duplication functionality.

The tunnel packet duplication statistics are displayed with real-time counter values showing packet processing metrics for the selected device.

Monitor tunnel information for a device

Monitor tunnel connection information for a device to view metrics such as loss percentage, latency, jitter, octets, and packet duplication counters.

Use tunnel monitoring to analyze the performance and health of tunnel connections on your devices. The monitoring interface provides detailed packet duplication counters and connection statistics to help troubleshoot network issues.

Procedure

Step 1

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

Step 2

Click a device name.

Step 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.

Step 4

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

Table 2. Packet duplication counters

Packet Duplication Counters

Description

Mapping to CLI Counters

RX

Displays the number of original packets received on this primary tunnel.

pktdup-RX

RX Fwd

Displays the number of original packets forwarded by this primary tunnel.

pktdup-RX-fwd

RX Dup Fwd

Displays the number of duplicated packets forwarded by duplicate tunnels.

RX Fwd + RX Dup Fwd = RX

pktdup-RX-fwd-dup-tun

TX Intercepted

Displays the number of packets intercepted for duplication.

pktdup-TX-intercepted

TX Dup

Displays the number of successful duplicate packets on the duplicate tunnel(s).

(pktdup-TX) - (pktdup-TX-dup-tun-sent-failed)

TX Dup Failed

Displays the number of failed duplications.

(pktdup-TX-dup-tun-selection-failed) + (pktdup-TX-dup-tun-sent-failed)

You can view tunnel connection information and packet duplication counters for the selected device in your chosen chart format.