QoS SGT
Feature Overview
QoS SGT is a functionality that allows ICX switches to mark specific types of traffic generated internally. This capability enables you to manage the priority at which ICX self-generated traffic traverses the network.
QoS SGT is based on the following well-established networking standards:
- IEEE 802.1p defines traffic classification and priority levels for Layer 2 Ethernet frames.
- IETF RFC 2474 governs the Differentiated Services (DiffServ) Code Point (DSCP) markings used in Layer 3 QoS.
The following table provides the default mappings of 802.1p priorities to DSCP values.
802.1p to DSCP Mapping
| 802.1p Priority | DSCP Marking Range | Traffic Class Description |
|---|---|---|
| 0 | 0-7 | Best effort |
| 1 | 8-15 | Background |
| 2 | 16-23 | Spare |
| 3 | 24-31 | Excellent effort |
| 4 | 32-39 | Controlled load |
| 5 | 40-47 | Video (<100 ms latency) |
| 6 | 48-55 | Video (<10 ms latency) |
| 7 | 56-63 | Network control |
Key Terms for Understanding QoS SGT Configuration
- Type: Predefined categories of network traffic, such as DNS, ICMP, SSH, NTP, Syslog, TELNET, TFTP, SNMP, and RADIUS, which can be configured with different priority markings.
- 802.1p Priority Marking: A VLAN tag field in Ethernet frames that assigns traffic priority levels ranging from 0 (lowest priority) to 7 (highest priority), allowing for differentiated handling of traffic based on its importance. It is particularly useful for real-time applications such as VoIP and video conferencing, which are sensitive to latency.
- DSCP Marking: Differentiated Services Code Point (DSCP) is a field in the IP header used to classify network traffic for QoS handling. It provides more granular traffic management with 64 different classes for implementing various QoS policies, such as traffic shaping, policing, and intelligent queuing.
QoS SGT operates through a structured process to validate QoS policies efficiently. You select a predefined traffic type (for example, DNS, ICMP, SNMP, or SSH) to generate within the network device. The system applies DSCP and 802.1p priority markings to the self-generated traffic, ensuring it receives proper treatment according to network policies. The device transmits the marked traffic through the network, allowing you to observe QoS enforcement. Finally, you monitor how the traffic is processed, identifying potential misconfigurations or areas for optimization.
Requirements
The following requirements must be met to enable this functionality on the controller.
Considerations
Ensure the following considerations are met.
- The QoS SGT marking affects only the traffic leaving the switch. To maintain consistent QoS treatment, subsequent switches in the network must honor these markings. However, traffic returning to the ICX switch may not retain the same markings unless configured in the responding device or somewhere along the network path.
- When this configuration is saved in the controller, it sends the necessary commands to the ICX switch to apply QoS parameters for the specified traffic type. The switch will mark this traffic during specific operations.
Limitations
Following are the limitations of this feature.
Best Practices
Follow these best practices when using the QoS SGT feature:
- After configuring QoS SGT, continuously monitor the network to ensure internally generated traffic is prioritized as expected. Performing packet captures to verify the QoS fields in the packets is recommended. This helps confirm that DSCP and 802.1p markings are correctly applied, identifying any misconfigurations or areas for optimization.
- Ensure that the QoS SGT configuration integrates optimally with existing QoS policies. It should not interfere with the prioritization of user traffic and critical applications.
Prerequisites
This feature has no prerequisites to feature enablement or usage.