Citrix SD-WAN

Classes

The Citrix SD-WAN configuration provides a default set of application and IP/Port based QoS policies that are applied to all traffic going over Virtual Paths. These settings can be customized to fit the deployment needs.

Classes are useful to prioritize the traffic. Application and IP/Port based QoS policies classify traffic and put it into appropriate classes specified in the configuration.

For more information on application QoS and IP address/port based QoS, see Rules by application name and Rules by IP address and port number respectively.

The SD-WAN provides 17 classes (IDs: 0–16). Following is the default configuration of all the 17 classes.

Virtual path default sets

The following are the different types of classes:

  • Real-time: Used for low latency, low bandwidth, time-sensitive traffic. Real-time applications are time sensitive but don’t really need high bandwidth (for example voice over IP). Real-time applications are sensitive to latency and jitter, but can tolerate some loss.

  • Interactive: Used for interactive traffic with low to medium latency requirements and low to medium bandwidth requirements. The interaction is typically between a client and a server. The communication might not need high bandwidth but is sensitive to loss and latency.

  • Bulk: Used for high bandwidth traffic and applications that can tolerate high latency. Applications that handle file transfer and need high bandwidth are categorized as bulk class. These applications involve little human interference and are mostly handled by the systems themselves.

Bandwidth sharing among classes

Bandwidth is shared among classes as follows:

  • Real-time: Traffic hitting real-time classes are guaranteed to have low latency and bandwidth is capped to the class share when there is competing traffic.

  • Interactive: Traffic hitting the interactive classes get remaining bandwidth after serving real-time traffic and the available bandwidth is fair shared among the interactive classes.

  • Bulk: Bulk is best effort. Bandwidth left over after serving real-time and interactive traffic is given to bulk classes on a fair share basis. Bulk traffic can starve if real-time and interactive traffic utilizes all the available bandwidth.

Note

Any class can use all available bandwidth when there is no contention.

The following example explains the bandwidth distribution based on the class configuration:

Consider there is an aggregated bandwidth of 10 Mbps over Virtual Path. If the class configuration is

  • Real-time: 30%
  • Interactive High: 40%
  • Interactive Medium: 20%
  • Interactive Low: 10%
  • Bulk: 100%

The bandwidth distribution outcome is

  • Real-time traffic gets 30% of 10Mbs (3 Mbps)

  • Interactive classes share the remaining bandwidth on fair share basis (4 Mbps: 2 Mbps: 1 Mbps)

  • Anything leftover when real-time, interactive traffic is not fully utilizing the shares is given to the Bulk class

To customize classes:

  1. If Virtual Path Default Sets are in use, classes can be modified under Global > Virtual Path Default Sets.

    Note

    You can also modify classes at the Virtual Path level (Connections -> Virtual Paths -> Classes)

  2. Click Add Default Set, enter a name for the default set, and click Add. In the Section field, select Classes.

  3. In the Name field, either leave the default name or enter a name of your choice.

  4. In the Type field, select the class type (Real-time, Interactive, or Bulk).

  5. For real-time classes, you can specify the following attributes:

    • Initial Period: The time period in milliseconds to apply an initial rate before switching to a sustained rate.

    • Initial Rate: Maximum rate or percentage at which packets leave the queue during the initial period.

    • Sustained Rate: Maximum rate or percentage at which the packets leave the queue after the initial period.

  6. For interactive classes, you can specify the following attributes:

    • Initial Period: The time period, in milliseconds, during which to apply the initial percentage of the available bandwidth before switching to the sustained percentage. Typically, 20 ms.

    • Initial Share %: The maximum share of virtual-path bandwidth remaining after serving real-time during the initial period.

    • Sustained Share %: The maximum share of virtual-path bandwidth remaining after serving real-time traffic after the initial period.

  7. For bulk classes, you can specify only the Sustained Share%, which determines the remaining virtual path bandwidth to be used for a bulk class after serving real-time and interactive traffic.

  8. Click Apply.

Note

Save the configuration, export it to the change management inbox, and initiate the change management process.

Classes