As long as there is policing or marking action in the policy, the class will have classification counters. Classification counters are not supported on pure queuing policies under any class-map. When there are multiple match statements in a class, the traffic counter is cumulative for all the match statements in the class. The device supports a total of eight table maps for policer exceed markdown and eight table maps for policer violate markdown. In a HQoS policy with parent shaping and child policy having priority level queuing and priority level policing, the statistics for policing are not updated.
Only QoS shaper statistics are updated. To view the QoS shaper statistics, use the show policy-map interface command in global configuration mode. Hierarchical queuing is unsupported in the same policy port shaper is the exception. In a parent class, all filters must have the same type. The child filter type must match the parent filter type with the following exceptions:.
If the parent class is configured to match IP, then the child class can be configured to match the ACL. If the parent class is configured to match CoS, then the child class can be configured to match the ACL.
The following are restrictions and considerations for applying QoS features on EtherChannel and channel member interfaces:. QoS is supported on EtherChannel member interfaces in both ingress and egression directions.
All EtherChannel members must have the same QoS policy applied. If the QoS policy is not the same, each individual policy on the different link acts independently. On attaching a service policy to channel members, the following warning message appears to remind the user to make sure the same policy is attached to all ports in the EtherChannel: ' Warning: add service policy will cause inconsistency with port xxx in ether channel xxx.
To create a traffic class containing match criteria, use the class-map command to specify the traffic class name, and then use the following match commands in class-map configuration mode, as needed.
All match commands specified in this configuration task are considered optional, but you must configure at least one match criterion for a class.
Enters the global configuration mode. Creates a class map to be used for matching packets to the class whose name you specify. This is the default. If match-any or match-all is not explicitly defined, match-all is chosen by default.
Since CPU generated packets are not marked at egress, the packet will not match the configured class-map. To create a traffic policy, use the policy-map global configuration command to specify the traffic policy name.
The traffic class is associated with the traffic policy when the class command is used. The class command must be entered after you enter the policy map configuration mode. After entering the class command, the device is automatically in policy map class configuration mode, which is where the QoS policies for the traffic policy are defined. Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy.
For a more detailed example of this command and its usage, see Configuring Bandwidth. For a more detailed example of this command and its usage, see Configuring Police. Optional Sets the strict scheduling priority for this class. Command options include:. Enter a value 1 or 2. For a more detailed example of this command and its usage, see Configuring Priority. Optional Configures the queue buffer for the class. Enter the queue buffers ratio limit 0 to For a more detailed example of this command and its usage, see Configuring Queue Buffers.
For a more detailed example of this command and its usage, see Configuring Queue Limits. For a more detailed example of this command and its usage, see Configuring Shaping. This procedure explains how to configure the following class-based packet marking features on your device :.
Enters policy class map configuration mode. Specifies the name of the class whose policy you want to create or change. This procedure describes the available configurations using set command options. The other command options admit , bandwidth , etc. Although this task lists all of the possible set commands, only one set command is supported per class. Values are from 0 to7. You can also set the following values using the set cos command:. In addition to setting specific DSCP values, you can also set the following using the set dscp command:.
Optional Sets IP specific values. You can set the following values using the set ip dscp command:. You can set the following values using the set ip precedence command:. You can set the following values using the set precedence command:. Optional Displays policy configuration information for all classes configured for all service policies. Attach the traffic policy to an interface using the service-policy command.
After the traffic class and traffic policy are created, you must use the service-policy interface configuration command to attach a traffic policy to an interface, and to specify the direction in which the policy should be applied either on packets coming into the interface or packets leaving the interface.
A traffic class and traffic policy must be created before attaching a traffic policy to an interface. Attaches a policy map to an input or output interface. This policy map is then used as the service policy for that interface. Proceed to attach any other traffic policy to an interface, and to specify the direction in which the policy should be applied.
Actions supported are remarking and policing. You should have already decided upon the classification, policing, and marking of your network traffic by policy maps prior to beginning this procedure.
If you specify match-any , one of the match criteria must be met for traffic entering the traffic class to be classified as part of the traffic class. Creates a policy map by entering the policy map name, and enters policy-map configuration mode.
By default, no policy maps are defined. Defines a traffic classification, and enter policy-map class configuration mode. By default, no policy map class-maps are defined. If a traffic class has already been defined by using the class-map global configuration command, specify its name for class-map-name in this command.
A class-default traffic class is predefined and can be added to any policy. It is always placed at the end of a policy map. With an implied match any included in the class-default class, all packets that have not already matched the other traffic classes will match class-default.
In this example, the police command adds a policer to the class where any traffic beyond the set target bit rate is dropped.
Returns to policy map configuration mode. Returns to global configuration mode. Specifies the port to attach to the policy map, and enters interface configuration mode. Valid interfaces include physical ports.
Specifies the policy-map name, and applies it to an ingress port. Only one policy map per ingress port is supported. Returns to privileged EXEC mode. Optional Verifies your entries. Optional Saves your entries in the configuration file. If applicable to your QoS configuration, configure classification, policing, and marking of traffic on SVIs by using policy maps.
You should have already decided upon the classification, policing, and marking of your network traffic by using policy maps prior to beginning this procedure. Defines a traffic classification, and enters the policy-map class configuration mode. Enter a value between and Table maps are a form of marking, and also enable the mapping and conversion of one field to another using a table. For example, a table map can be used to map and convert a Layer 2 CoS setting to a precedence value in Layer 3.
A table map can be referenced in multiple policies or multiple times in the same policy. A table map configured for a custom output policy under the default class-map, takes affect for all DSCP traffic regardless of which class map the traffic is classified for. The workaround is to remove the table map and configure the set dscp command under the default class to change the DSCP marking for classified traffic. If there is any non-queuing action policer or marking on a user-defined class, then the packet retains its value or remarks in the user-defined class itself.
Enters global configuration mode. Creates a table map and enters the table map configuration mode. In table map configuration mode, you can perform the following tasks:. The mapping from CoS values to DSCP values in this example is configured by using the set policy map class configuration command as described in a later step in this procedure. If this policy is applied on input port, that port will have trust DSCP enabled on that port and marking will take place depending upon the specified table map.
Configure any additional policy maps for QoS for your network. After creating your policy maps, attach the traffic policy or polices to an interface using the service-policy command. Command options for policy class map configuration mode include the following:. The queue can oversubscribe bandwidth in case other queues do not utilize the entire port bandwidth. The total sum cannot exceed percent, and in case it is less than percent, the rest of the bandwidth is equally divided along all bandwidth queues.
After creating the policy maps, attach the traffic policy or polices to an interface using the service-policy command. The following police subcommand options are available:. The following police conform-action transmit exceed-action subcommand options are available:.
Policer-based markdown actions are only supported using table maps. Only one markdown table map is allowed for each marking field in the. The show policy-map command output does not display counters for conformed bytes and exceeded bytes. This procedure explains how to configure priority on your device. Optional The priority command assigns a strict scheduling priority for the class. Priority level 1 is more important than priority level 2. Priority level 1 reserves bandwidth that is processed first for QoS, so its latency is very low.
Both priority level 1 and 2 reserve bandwidth. Depending on the complexity of your network and your QoS solution, you may need to perform all of the procedures in this section. You need to make decisions about these characteristics:. What drop percentage thresholds apply to the queues, and how much reserved and maximum memory is needed for the traffic type? How much of the fixed buffer space is allocated to the queues? Does the bandwidth of the port need to be rate limited? How often should the egress queues be serviced and which technique shaped, shared, or both should be used?
The allows you to allocate buffers to queues. If there is no allocation made to buffers, then they are divided equally for all queues. You can use the queue-buffer ratio to divide it in a particular ratio.
You should have created a class map for the queue buffer before beginning this procedure. You must have configured either bandwidth, shape, or priority on the policy map prior to configuring the queue buffers.
The range is to Ensure sufficient buffers are allocated to these queues for the protocols to function. WTD ensures the configuration of more than one threshold per queue. Each class of service is dropped at a different threshold value to provide for QoS differentiation. With the , each queue has 3 explicit programmable threshold classes—0, 1, 2. WTD also uses a soft limit, and therefore you are allowed to configure the queue limit to up to percent maximum four times the reserved buffer from common pool.
This soft limit prevents overrunning the common pool without impacting other features. You should have created a class map for the queue limits before beginning this procedure. You must have configured either bandwidth, shape, or priority on the policy map prior to configuring the queue limits.
Configures the bandwidth for the policy map. The parameters include:. With every queue, there are three thresholds 0,1,2 , and there are default values for each of these thresholds. Use this command to change the default or any other queue limit threshold setting. For example, if DSCP 3, 4, and 5 packets are being sent into a specific queue in a configuration, then you can use this command to set the threshold percentages for these three DSCP values.
For additional information about queue limit threshold values, see Weighted Tail Drop. The does not support absolute queue-limit percentages.
Proceed to configure any additional policy maps for QoS for your network. After creating your policy maps, proceed to attach the traffic policy or polices to an interface using the service-policy command. You use the shape command to configure shaping maximum bandwidth for a particular class. The queue's bandwidth is restricted to this value even though the port has additional bandwidth left.
You can configure shaping as an average percent, as well as a shape average value in bits per second. Configures the average shape rate. You can configure the average shape rate by target bit rates bits per second or by percentage of interface bandwidth for the Committed Information Rate CIR.
The following commands can be used to monitor QoS on the. Displays a list of all class maps configured. Displays a list of all policy maps configured.
Command parameters include:. After creating a class map by using an ACL, you then create a policy map for the class, and apply the policy map to an interface for QoS. This example shows how to classify packets for QoS using a class of service Layer 2 classification:.
After creating a class map by using a CoS Layer 2 classification, you then create a policy map for the class, and apply the policy map to an interface for QoS. After creating a class map by using a DSCP classification, you then create a policy map for the class, and apply the policy map to an interface for QoS. After creating a class map by using a VLAN Layer 2 classification, you then create a policy map for the class, and apply the policy map to an interface for QoS. After creating a class map by using a DSCP or precedence values, you then create a policy map for the class, and apply the policy map to an interface for QoS.
The following is an example of a hierarchical classification, where a class named parent is created, which matches another class named child.
The class named child matches based on the IP precedence being set to 2. After creating the parent class map, you then create a policy map for the class, and apply the policy map to an interface for QoS. This example describes how to classify packet streams for voice and video using device specific information. Assume that all the packets from the both the interfaces are sent on the uplink interface, and there is a requirement to police voice to Mbps and video to Mbps. The action for this class is to mark the qos-group to To match packets with QoS-group 10 on the output interface, a class named voice is created which matches on QoS-group This is then associated to another policy named output-interface, which is associated to the uplink interface.
Video is handled in the same way, but matches on QoS-group The following example shows how classify using the above device specific information:. After configuring the class maps, policy map, and shape averages for your configuration, proceed to then apply the policy map to the interface for QoS. The following example shows how to configure a queue-limit policy based upon DSCP values and percentages:.
After finishing with the above policy map queue-limit configuration, you can then proceed to apply the policy map to an interface for QoS. The following example shows how configure a queue buffer policy and then apply it to an interface for QoS:.
The following example displays the various policing actions that can be associated to the policer. These actions are accomplished using the conforming, exceeding, or violating packet configurations. You have the flexibility to drop, mark and transmit, or transmit packets that have exceeded or violated a traffic profile. For example, a common deployment scenario is one where the enterprise customer polices traffic exiting the network towards the service provider and marks the conforming, exceeding and violating packets with different DSCP values.
The service provider could then choose to drop the packets marked with the exceeded and violated DSCP values under cases of congestion, but may choose to transmit them when bandwidth is available.
One useful feature is the ability to associate multiple actions with an event. For example, you could set the precedence bit and the CoS for all conforming packets. A submode for an action configuration could then be provided by the policing feature. In this example, the exceed-markdown-table and violate-mark-down-table are table maps.
Only one markdown table map is allowed for each marking field in the device. The following example displays a VLAN policer configuration. The policing unit is the basis on which the token bucket works.
The burst parameters are specified in bytes. This is the default mode; it is the unit that is assumed when no units are specified. The CIR and PIR can also be configured in percent, in which case the burst parameters have to be configured in milliseconds. The following is an example of a policer configuration in bits per second. In this configuration, a dual-rate three-color policer is configured where the units of measurement is bits.
The burst and peak burst are all specified in bits. Policer based markdown actions are only supported using table maps. The following steps and examples show how to use table map marking for your QoS configuration:. Define the table-map using the table-map command and indicate the mapping of the values. This table does not know of the policies or classes within which it will be used. In the example, a table map named table-map1 is created.
The mapping defined is to convert the value from 0 to 1 and from 2 to 3, while setting the default value to 4. The following example shows how to use table maps to retain CoS markings on an interface for your QoS configuration.
The cos-trust-policy policy configured in the example is enabled in the ingress direction to retain the CoS marking coming into the interface. If the policy is not enabled, only the DSCP is trusted by default.
If a pure Layer 2 packet arrives at the interface, then the CoS value will be rewritten to 0 when there is no such policy in the ingress port for CoS. Review the auto-QoS documentation to see if you can use these automated capabilities for your QoS configuration. To help you research and resolve system error messages in this release, use the Error Message Decoder tool. The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.
Access to most tools on the Cisco Support website requires a Cisco. This table provides release and related information for features explained in this module. These features are available on all releases subsequent to the one they were introduced in, unless noted otherwise. QoS provides preferential treatment to specific types of traffic at the expense of other traffic types.
Use Cisco Feature Navigator to find information about platform and software image support. Skip to content Skip to search Skip to footer. Book Contents Book Contents. Find Matches in This Book. PDF - Complete Book 2. Updated: October 22, Chapter: Configuring QoS. Understanding of QoS implementation. QoS Terminology The following terms are used interchangeably in this QoS configuration guide: Upstream direction towards the device is the same as ingress.
Downstream direction from the device is the same as egress. Information About QoS QoS Overview By configuring the quality of service QoS , you can provide preferential treatment to specific types of traffic at the expense of other traffic types.
Table 1. Supported number of queues at port level Up to 8 queues supported on a port. HQoS allows you to perform: Hierarchical classification— Traffic classification is based upon other classes. Note Hierarchical shaping is only supported for the port shaper, where for the parent you only have a configuration for the class default, and the only action for the class default is shaping.
QoS Implementation Typically, networks operate on a best-effort delivery basis, which means that all traffic has equal priority and an equal chance of being delivered in a timely manner. Figure 1. End-to-End QoS Solution Using Classification All switches and routers that access the Internet rely on the class information to provide the same forwarding treatment to packets with the same class information and different treatment to packets with different class information.
Packet Classification Packet classification is the process of identifying a packet as belonging to one of several classes in a defined policy, based on certain criteria. The policy class language is used to define the following: Class-map template with one or several match criteria Policy-map template with one or several classes associated to the policy map The policy map template is then associated to one or several interfaces on the device.
Packet classification can be categorized into the following types: Classification based on information that is propagated with the packet Classification based on information that is device specific Hierarchical classification Classification Based on Information That is Propagated with the Packet Classification Based on Information that is Device Specific Hierarchical Classification Classification Based on Information That is Propagated with the Packet Classification that is based on information that is part of the packet and propagated either end-to-end or between hops, typically includes the following: Classification based on Layer 3 or 4 headers Classification based on Layer 2 information Classification Based on Layer 3 or Layer 4 Header Classification Based on Layer 2 Header Classification Based on Layer 3 or Layer 4 Header This is the most common deployment scenario.
Table 2. Some fields in Layer 2 header can also be set uing a policy. Classification Based on Layer 2 Header A variety of methods can be used to perform classification based on the Layer 2 header information. The most common methods include the following: MAC address-based classification only for access groups —Classification is based upon the source MAC address for policies in the input direction and destination MAC address for policies in the output direction.
Note Some of these fields in the Layer 2 header can also be set using a policy. Classification Based on Information that is Device Specific The device also provides classification mechanisms that are available where classification is not based on information in the packet header or payload.
Hierarchical Classification The device permits you to perform a classification based on other classes. Egress Port Activity The following activities occur at the egress port of the device : Policing—Policing determines whether a packet is in or out of profile by comparing the rate of the incoming traffic to the configured policer.
Classification Classification is the process of distinguishing one kind of traffic from another by examining the fields in the packet. In the QoS context, the permit and deny actions in the access control entries ACEs have different meanings from security ACLs: If a match with a permit action is encountered first-match principle , the specified QoS-related action is taken.
Note When creating an access list, note that by default the end of the access list contains an implicit deny statement for everything if it did not find a match before reaching the end. Class Maps A class map is a mechanism that you use to name a specific traffic flow or class and isolate it from all other traffic. Note You cannot configure IPv4 and IPv6 classification criteria simultaneously in the same class-map.
Policy Maps A policy map specifies which traffic class to act on. Actions can include the following: Setting a specific DSCP or IP precedence value in the traffic class Setting a CoS value in the traffic class Setting a QoS group Specifying the traffic bandwidth limitations and the action to take when the traffic is out of profile Before a policy map can be effective, you must attach it to a port.
Note You cannot configure both priority and set for a policy map. If both these commands are configured for a policy map, and when the policy map is applied to an interface, error messages are displayed. A policy map also has these characteristics: A policy map can contain multiple class statements, each with different match criteria and policers.
Note All traffic, regardless of whether it is bridged or routed, is subjected to a policer, if one is configured. You can only configure policing on a physical port.
Marking Marking is used to convey specific information to a downstream device in the network, or to carry information from one interface in a device to another.
Switch Specific Information Marking This form of marking includes marking of fields in the packet data structure that are not part of the packets header, so that the marking can be used later in the data path. Table Map Marking Table map marking enables the mapping and conversion from one field to another using a conversion table. The following table shows the currently supported forms of mapping: Table 3. Rewrite—Packets coming in are rewritten depending upon the configured table map.
Mapping—Table map based policies can be used instead of set policies. The following steps are required for table map marking: Define the table map—Use the table-map global configuration command to map the values. Define the policy map—You must define the policy map where the table map will be used. Associate the policy to an interface. Note A table map policy on an input port changes the trust setting of that port to the from type of qos-marking.
Traffic Conditioning To support QoS in a network, traffic entering the service provider network needs to be policed on the network boundary routers to ensure that the traffic rate stays within the service limit.
Note When running QoS tests on network traffic, you may see different results for the shaper and policing data. This table compares the policing and shaping functions. Table 4. Smooths traffic and sends it out at a constant rate. When tokens are exhausted, action is taken immediately. Shaping has only one unit of configuration - in bits per second. Shaping does not have the provision to mark packets that do not meet the profile. Works for both input and output traffic. Implemented for output traffic only.
Policing Shaping Policing The QoS policing feature is used to impose a maximum rate on a traffic class. The following policing forms or policers are supported for QoS: Single-rate two-color policing Dual-rate three-color policing Note Single-rate three-color policing is not supported.
Note For information about the token-bucket algorithm, see Token-Bucket Algorithm. Dual-Rate Three-Color Policing With the dual rate policer, the device supports only color-blind mode. The following shaping forms are supported in a class: Average rate shaping Hierarchical shaping Shaping is implemented using a token bucket. Hierarchical Shaping Shaping can also be configured at multiple levels in a hierarchy. There are two supported types of hierarchical shaping: Port shaper User-configured shaping The port shaper uses the class default and the only action permitted in the parent is shaping.
Queuing and Scheduling The uses both queuing and scheduling to help prevent traffic congestion. The supports the following queuing and scheduling features: Bandwidth Weighted Tail Drop Priority queues Queue buffers When you define a queuing policy on a port, control packets are mapped to the best priority queue with the highest threshold.
Control packets queue mapping works differently in the following scenarios: Without a quality of service QoS policy—If no QoS policy is configured, control packets with DSCP values 16, 24, 48, and 56 are mapped to queue 0 with the highest threshold of threshold2. Note Queuing policy in egress direction does not support match access-group classification. Control traffic is redirected to the best queue based on the following rules: If defined in a user policy, the highest- level priority queue is always chosen as the best queue.
Note To provide proper QoS for Layer 3 packets, you must ensure that packets are explicitly classified into appropriate queues. Bandwidth Weighted Tail Drop Priority Queues Queue Buffer Bandwidth The supports the following bandwidth configurations: Bandwidth percent Bandwidth remaining ratio Bandwidth Percent Bandwidth Remaining Ratio Bandwidth Percent You can use the bandwidth percent policy-map class command to allocate a minimum bandwidth to a particular class.
Note A queue can oversubscribe bandwidth in case the other queues do not utilize the entire port bandwidth. Bandwidth Remaining Ratio You use the bandwidth remaining ratio policy-map class command to create a ratio for sharing unused bandwidth in specified queues.
Weighted Tail Drop The egress queues use an enhanced version of the tail-drop congestion-avoidance mechanism called weighted tail drop WTD. Figure 2. WTD and Queue Operation. The following figure shows an example of WTD operating on a queue whose size is frames. Three drop percentages are configured: 40 percent frames , 60 percent frames , and percent frames. These percentages indicate that up to frames can be queued at the percent threshold, up to frames at the percent threshold, and up to frames at the percent threshold.
This time, let's take a step back and look at how to configure basic QoS for a given scenario using a downloadable template. Let's begin with a sample scenario. Let's say you have a Cisco W router at home. However, you're experiencing performance issues with your Skype phone service when simultaneously surfing the Web.
When downloading a file, your phone service sounds horrible. In addition, your Internet game suffers when you download FTP files.
This is a prime example of how QoS comes in handy—you need to give these different types of traffic the bandwidth and the priority they require. Once you've configured QoS, you should be able to talk on the phone, play your game, and download files—all at the same time—without experiencing any performance issues.
Keep in mind that this is only an example. Once you understand how to configure QoS, you can customize it to fit your organization's needs. In addition, the downloadable template will create the configuration file, and you can modify it to fit your company's needs.
An ACL is the traditional way to define any traffic for a router. But there's a limited list of protocols and applications that the router recognizes.
While the router won't recognize every single application, each IOS upgrade adds more to the list. If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information ciscopress.
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Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions. All rights reserved. Cisco Press. Join Sign In. Date: May 13, Chapter Description This chapter describes how QoS is an integral part of any multilayer switched network deployment.
With QoS, you can build a network of predictable behavior for latency, jitter, and packet loss. In addition, QoS mitigates anomalous network behavior and provides for differentiation of traffic flows. Overview Pearson Education, Inc. Collection and Use of Information To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including: Questions and Inquiries For inquiries and questions, we collect the inquiry or question, together with name, contact details email address, phone number and mailing address and any other additional information voluntarily submitted to us through a Contact Us form or an email.
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