What Cisco feature uses a priority queue for traffic that needs to be delivered?
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You cannot specify the same priority level for two different classes in the same policy map. For example, the device does not accept the following configuration: Show You cannot configure the default queue as a priority queue at any level. You cannot configure the bandwidth command and multi-level priority queues on the same class. For example, the device rejects the following configuration: You cannot configure the shape command and multi-level priority queues on the same class. For example, the device rejects the following configuration: To convert a one-level (flat) service policy with multiple priority queues configured to a hierarchical multi-level priority queues service policy, you must first detach the flat service policy from the interface using the no service-policy command and then add a child policy map to it. We recommend not to use MPQ at the logical level, that is, under the class-map containing match for the VLANs . The priority command is used to specify that a class of traffic has latency requirements with respect to other classes. For multiple priority queues, you can use the priority level command to configure a level of priority service on a class in a policy map. The device places traffic with a high-priority level on the outbound link ahead of traffic with a low-priority level. High-priority packets, therefore, are not delayed behind low-priority packets. The device services the high-level priority queues until empty before servicing the next-level priority queues and non-priority queues. While the device services a queue, the service rate is as fast as possible and is constrained only by the rate of the underlying link or parent node in a hierarchy. If a rate is configured and the device determines that a traffic stream has exceeded the configured rate, the device drops the exceeding packets during periods of congestion. If the link is currently not congested, the device places the exceeding packets onto the outbound link. When configuring MPQ on different traffic classes in a policy map, you must specify different priority levels for the traffic classes. For example, configure one traffic class to have priority level 2 and another class to have priority level 1. Note In a hierarchical MPQ configuration in which all traffic is sent through the level-2 priority queue only, the traffic sent through the level-2 priority queue receives the same treatment as the traffic sent through the level-1 priority queue. You cannot configure the priority command and the priority level command on different classes in the same policy map. Before you beginThe traffic classes, class maps, and policy maps must exist. SUMMARY STEPS
DETAILED STEPSCommand or ActionPurposeStep 1enable Example:Enables privileged EXEC mode.
configure terminal Example:Enters global configuration mode. Step 3policy-map policy-name Example:Creates or modifies a policy map and enters policy-map configuration mode.
class class-name Example:Specifies a traffic class and enters policy-map class configuration mode.
priority level level Example:Assigns priority to a traffic class at the priority level specified.
Do not specify the same priority level for two different classes in the same policy map. Step 6end Example:(Optional) Exits policy-map class mode. SUMMARY STEPS
DETAILED STEPSCommand or ActionPurposeStep 1enable Example:Enables privileged EXEC mode.
show policy-map interface type number Example:Displays the packet statistics of all classes that are configured for all service policies either on the specified interface or subinterface or on a specific PVC on the interface.
exit Example:(Optional) Exits privileged EXEC mode. The following example shows how to configure multiple priority queues with 2 level priority. The policy map named Business has two traffic classes: Bronze and Gold. Bronze traffic has a level 2 (low) priority, whereas Gold traffic has a level 1 (high) priority. To prevent bandwidth starvation of Bronze traffic, the Gold traffic is policed at 30 percent of the interface bandwidth. The following example shows how to configure multiple priority queues with 7 level priority. The policy map named Business has seven traffic classes: Platinum, Gold, Silver, Bronze, Iron, Aluminium, and Steel. Steel traffic has a level 7 (lowest) priority, whereas Platinum traffic has a level 1 (highest) priority. To prevent bandwidth starvation, the Platinum and Gold traffic is policed at 30 percent and 20 percent respectively, of the interface bandwidth. Related DocumentsRelated Topic Document Title QoS commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples Cisco IOS Quality of Service Solutions Command Reference Priority queues, creating classes, class maps, and policy maps “Applying QoS Features Using the MQC” module Technical AssistanceDescription Link The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. Which QOS queue has priority?The switch supports eight queues for each interface. Queue number 8 is the highest priority queue.
What is the queuing strategy in Cisco?Weighted Fair Queuing (WFQ)
WFQ is one of Cisco's premier queuing techniques. It is a flow-based queuing algorithm that does two things simultaneously: It schedules interactive traffic to the front of the queue to reduce response time, and it fairly shares the remaining bandwidth between high bandwidth flows.
What are the four priority queues used with QOS priority?QOS is implemented as rules or policies that prioritize packets, optionally change information in the packet header, and assign them to outbound port queues based on their priority. Each switch port has four types of outbound traffic queues based on priority: low, normal, medium, and high.
What is priority queuing in networking?In computer science, a priority queue is an abstract data-type similar to a regular queue or stack data structure in which each element additionally has a priority associated with it. In a priority queue, an element with high priority is served before an element with low priority.
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