About Quality of Service for network traffic

Quality of Service (QoS) is a set of service requirements that the network must meet to ensure an adequate service level for data transmission. The goal of QoS is a guaranteed delivery system for network traffic.

The QoS feature enables administrators to configure traffic queues for different priority network traffic, categorize and prioritize ingress traffic, and adjust priority settings on egress traffic. Administrators can use these settings to ensure that important traffic receives the highest priority handling while less important traffic is handled at a lower priority. Network traffic is categorized, and then classified. After being classified, traffic is given priorities and scheduled for transmission.

For end-to-end QoS, all hops along the way must be configured with similar QoS policies of classification and traffic management. Traffic prioritization happens because of two things in an end-to-end QoS policy.
  • At the interconnect, the packets are egressed based on the associated queue bandwidth. The more the bandwidth, the higher the priority for the associated traffic at the queue.

  • Egress dot1p remarking helps achieve priority at the next hops in the network. If the queue egress traffic is remarked to a dot1p value, and that dot1p value is mapped to a queue in the next hops with higher bandwidth, then these packets in the end-to-end network are treated with higher priority.

QoS configuration is defined in the logical interconnect group and applied to the logical interconnect. QoS statistics are collected by the interconnects.

A QoS configuration is applied only on VC Ethernet and VC FlexFabric interconnects on c7000 enclosures.

Consistency state of a logical interconnect with QoS configurations

The UI displays only the currently active QoS configuration that is applied on the interconnects. In addition, two inactive QoS configurations are stored for Custom (with FCoE) and Custom (without FCoE) configuration types. These inactive configurations are the last known QoS configurations for the corresponding configuration types, applied previously on the associated logical interconnect, and logical interconnect group.

While checking for consistency of a logical interconnect to its associated logical interconnect group, the compliance of inactive QoS configurations is also checked (inactive QoS configurations are not visible in the UI). Even if active QoS configurations are same between a logical interconnect and associated logical interconnect group, because of inconsistencies in inactive QoS configurations stored internally, a logical interconnect consistency status can be shown as Inconsistent.

Perform an Update from group to bring the logical interconnect group and logical interconnect into a consistent state.