Quality of Service (QoS)

A Quality of Service (QoS) policy ensures data transfer in accordance with the requirements set for traffic classes. In Kaspersky SD-WAN, the following components contribute to the quality of service:

• Traffic classes are used to queue and prioritize traffic. For example, one of the classes can be used for real-time traffic that requires minimizing packet loss.
• Traffic classifiers determine whether or not to trust DSCP values (Differentiated Services Code Point) set in the traffic packet header fields; they also map DSCP values to traffic classifiers.
• QoS rules determine whether the bandwidth of traffic processed by traffic classifiers is limited.
• Constraints are used in transport services for SLA compliance. You can create two types of constraints:
  • Manual TE constraints are used to add Manual-TE paths to transport services. When configuring this type of constraints, you can enable the use of an Auto-SPF path if Manual-TE paths are not available.
  • Threshold constraints are used to build Auto-TE routes in transport services based on threshold values of monitoring indicators.

  If a link used in a transport service reaches the threshold values of the selected monitoring indicators, this link is completely or partially excluded from the Auto-TE path calculation. Partially excluded links can be taken into account when calculating the Auto-TE path if there are no alternative links satisfying the constraint.

  For example, you can create a constraint that completely excludes from the Auto-TE path calculation those links that have reached the packet loss threshold. Thus, in a transport service that uses this constraint, traffic only travels through links that have low packet loss.

• Traffic classification rules are used to identify traffic with particular values of the L2 – L4 header fields, as well as traffic of specified applications, in the overall stream of traffic. For each traffic classification rule, you must specify a sequence number and select a default action, which allows or prohibits further routing of the traffic. Classification rules are added to traffic filters.
• Traffic filters are used to ensure security by blocking excessive or dangerous traffic, to classify traffic, and to comply with SLA requirements for applications. Each filter consists of one or more traffic classification rules.

A maximum of 8 traffic queues can be used on the WAN and LAN interfaces. For each queue, you must specify the minimum and maximum bandwidth as a percentage of the total bandwidth set for the interface as a whole. The sum total of all minimum bandwidth values specified for queues may not exceed 100%.

The queues are strict priority and unreserved bandwidth is first offered to traffic from the higher-priority queue. Each queue is guaranteed certain minimum bandwidth in accordance with its specified minimum bandwidth value. An upper limit on the maximum bandwidth for higher-priority queues is necessary to allow traffic from lower-priority queues to still be transmitted.

You can configure queues when creating or editing WAN interfaces. Due to the fact that Kaspersky SD-WAN does not support creating LAN interfaces, queues can only be configured for LAN interfaces that already exist.

Service providers can use different QoS policies to mark queues in their networks and meet the requirements of service level agreements (SLA) for the passage of client traffic. Therefore, when CPE devices are connected to communication channels of different service providers, the CPE devices can flexibly relabel traffic of different queues for each WAN interface. To configure relabelling, you must change the value of the type of service (hereinafter also referred to as ToS) when configuring queues on the SD-WAN interface.

You can edit only the ToS values of the external (link) headers of traffic packets going out of the WAN interfaces. ToS values of internal traffic packet headers cannot be edited.