QoS Application#

Quality of Service (QoS) is a set of technologies and mechanisms used to manage traffic prioritization, often but not exclusively used in scenarios of network congestion. A full explanation of QoS is beyond the scope of this documentation, as the concepts are often as complex as the implementation of them on various network operating systems, along with chip-specific capabilities and limitations.

When a packet enters through a physical interface, a specific IngressPolicy inspects the headers of the packet and assigns it a ForwardingClass and (optionally) a color or drop probability.

Based on the ForwardingClass and/or color, the packet may be sent to a policer for rate-limiting. If the packet is not dropped, the router decides where the packet needs to go and assigns it to a Queue. When a packet enters a Queue, it is either dropped because the Queue is full, discarded by a slope policy, or accepted.

The EgressPolicy then (optionally) converts the ForwardingClass to priority bits, after which the scheduler empties the queue and sends the packets out to the next hop in the network.

Policies are applied to (sub)interfaces by creating either a PolicyDeployment or a PolicyAttachment resource.

The application provides the following components: