- Cisco IOS Quality of Service Solutions Configuration Guide, Release 12.1
Table Of Contents
Configuring Weighted Fair Queueing
Flow-Based Weighted Fair Queueing Configuration Task List
VIP-Distributed Weighted Fair Queueing Configuration Task List
Configuring QoS-Group-Based DWFQ
Class-Based Weighted Fair Queueing Configuration Task List
Configuring Class Policy in the Policy Map
Configuring Class Policy Using Tail Drop
Configuring Class Policy Using WRED Packet Drop
Configuring the Class-Default Class Policy
Attaching the Service Policy and Enabling CBWFQ
Modifying the Bandwidth for an Existing Policy Map Class
Modifying the Queue Limit for an Existing Policy Map Class
Configuring the Bandwidth Limiting Factor
Verifying Configuration of Policy Maps and Their Classes
IP RTP Priority Configuration Task List
Configuring the Bandwidth Limiting Factor
Monitoring and Maintaining IP RTP Priority
Frame Relay IP RTP Priority Configuration Task List
Configuring Frame Relay IP RTP Priority
Verifying Frame Relay IP RTP Priority
Monitoring and Maintaining Frame Relay IP RTP Priority
Low Latency Queueing Configuration Task List
Configuring Low Latency Queueing
Configuring the Bandwidth Limiting Factor
Verifying Low Latency Queueing
Monitoring and Maintaining Low Latency Queueing
Flow-Based WFQ Configuration Examples
Class Map Configuration Example
Policy Attachment to Interfaces Example
CBWFQ Using WRED Packet Drop Example
Display Service Policy Map Content Examples
IP RTP Priority Configuration Examples
Virtual Template Configuration Example
Multilink Bundle Configuration Example
Frame Relay IP RTP Priority Configuration Examples
Strict Priority Service to Matching RTP Packets Example
Low Latency Queueing Configuration Examples
Virtual Template Configuration Example
Multilink Bundle Configuration Example
Configuring Weighted Fair Queueing
This chapter describes the tasks for configuring weighted fair queueing (WFQ), VIP-Distributed WFQ (DWFQ), and class-based WFQ (CBWFQ) and the following related features, which provide strict priority queueing within WFQ or CBWFQ:
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IP RTP Priority Queueing
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For complete conceptual information, see the section "Weighted Fair Queueing" in the chapter "Congestion Management Overview" in this book.
For a complete description of the QoS commands in this chapter, refer to the Cisco IOS Quality of Service Solutions Command Reference. To locate documentation of other commands that appear in this chapter, use the command reference master index, or search online.
Flow-Based Weighted Fair Queueing Configuration Task List
WFQ provides traffic priority management that automatically sorts among individual traffic streams without requiring that you first define access lists (ACLs). WFQ can also manage duplex data streams such as those between pairs of applications, and simplex data streams such as voice or video. There are two categories of WFQ sessions: high bandwidth and low bandwidth. Low-bandwidth traffic has effective priority over high-bandwidth traffic, and high-bandwidth traffic shares the transmission service proportionally according to assigned weights.
When WFQ is enabled for an interface, new messages for high-bandwidth traffic streams are discarded after the configured or default congestive messages threshold has been met. However, low-bandwidth conversations, which include control message conversations, continue to enqueue data. As a result, the fair queue may occasionally contain more messages than its configured threshold number specifies.
With standard WFQ, packets are classified by flow. Packets with the same source IP address, destination IP address, source TCP or User Datagram Protocol (UDP) port, or destination TCP or UDP port belong to the same flow. WFQ allocates an equal share of the bandwidth to each flow. Flow-based WFQ is also called fair queueing because all flows are equally weighted.
The Cisco IOS software provides two forms of flow-based WFQ:
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To configure flow-based WFQ, perform the tasks in the following sections. The first section is required; the other section is optional.
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Flow-based WFQ is supported on unavailable bit rate (UBR), variable bit rate (VBR), and available bit rate (ABR) ATM connections.
See the end of this chapter for the section "Flow-Based WFQ Configuration Examples."
Configuring WFQ
To configure flow-based fair queueing on an interface, use the following command in interface configuration mode:
Router(config-if)# fair-queue [congestive-discard-threshold [dynamic-queues [reservable-queues]]]
Configures an interface to use fair queueing.
Flow-based WFQ uses a traffic data stream discrimination registry service to determine to which traffic stream a message belongs. See the table accompanying the description of the fair-queue (WFQ) command in the Cisco IOS Quality of Service Solutions Command Reference for the attributes of a message that are used to classify traffic into data streams.
Defaults are provided for the congestion threshold after which messages for high-bandwidth conversations are dropped, and for the number of dynamic and reservable queues; however, you can fine-tune your network operation by changing these defaults. See the tables accompanying the description of the fair-queue (WFQ) command in the Cisco IOS Quality of Service Solutions Command Reference for the default number of dynamic queues that WFQ and CBWFQ use when they are enabled on an interface or ATM VC. These values do not apply for DWFQ.
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Monitoring Fair Queueing
To monitor flow-based fair queueing services in your network, use one or more of the following commands in EXEC mode:
VIP-Distributed Weighted Fair Queueing Configuration Task List
To configure DWFQ, perform one of the following mutually-exclusive tasks:
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If you enable flow-based DWFQ and then enable class-based DWFQ (either QoS-group based or ToS-based), class-based DWFQ will replace flow-based DWFQ.
If you enable class-based DWFQ and then want to switch to flow-based DWFQ, you must disable class-based DWFQ using the no fair-queue class-based command before enabling flow-based DWFQ.
If you enable one type of class-based DWFQ and then enable the other type, the second type will replace the first.
DWFQ runs only on Cisco 7000 series routers with a Route Switch Processor-based RSP7000 interface processor or Cisco 7500 series routers with a VIP-based VIP2-40 or greater interface processor. (A VIP2-50 interface processor is strongly recommended when the aggregate line rate of the port adapters on the VIP is greater than DS3. A VIP2-50 interface processor is required for OC-3 rates.)
DWFQ can be configured on interfaces but not subinterfaces. It is not supported on Fast EtherChannel, tunnel, or other logical or virtual interfaces such as MLP.
Configuring Flow-Based DWFQ
To configure flow-based DWFQ, use the following commands in interface configuration mode:
For flow-based DWFQ, packets are classified by flow. Packets with the same source IP address, destination IP address, source TCP or UDP port, destination TCP or UDP port, and protocol belong to the same flow.
In general, you should not change the aggregate or individual limit value from the default. Use the fair-queue aggregate-limit and fair-queue individual-limit commands only if you have determined that you would benefit from using different values, based on your particular situation.
Configuring QoS-Group-Based DWFQ
To configure QoS-group-based DWFQ, use the following commands in interface configuration mode:
In general, you should not change the aggregate, individual, or class limit value from the default. Use the fair-queue aggregate-limit, fair-queue individual-limit, and fair-queue limit commands only if you have determined that you would benefit from using different values, based on your particular situation.
Configuring ToS-Based DWFQ
To configure ToS-based DWFQ, use the following commands in interface configuration mode:
In general, you should not change the aggregate, individual, or class limit value from the default. Use the fair-queue aggregate-limit, fair-queue individual-limit, and fair-queue limit commands only if you have determined that you would benefit from using different values, based on your particular situation.
Monitoring DWFQ
To monitor DWFQ, use one or more of the following commands in EXEC mode:
Router# show interfaces [interface]
Displays statistical information specific to an interface.
Router# show queueing fair-queue
Displays status of the fair queueing configuration.
Class-Based Weighted Fair Queueing Configuration Task List
To configure CBWFQ, perform the tasks in the following sections. The first three sections are required; the remaining sections are optional.
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CBWFQ is supported on VBR and ABR ATM connections. It is not supported on UBR connections.
See the end of this chapter for the section "CBWFQ Configuration Examples."
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Defining Class Maps
To create a class map containing match criteria against which a packet is checked to determine if it belongs to a class—and to effectively create the class whose policy can be specified in one or more policy maps—use the first command in global configuration mode to specify the class map name, then one of the following commands in class map configuration mode:
Configuring Class Policy in the Policy Map
To configure a policy map and create class policies that make up the service policy, use the policy-map command to specify the policy map name, then use one or more of the following commands to configure policy for a standard class or the default class:
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For each class that you define, you can use one or more of the listed commands to configure class policy. For example, you might specify bandwidth for one class and both bandwidth and queue limit for another class.
The default class of the policy map (commonly known as the class-default class) is the class to which traffic is directed if that traffic does not satisfy the match criteria of other classes whose policy is defined in the policy map.
You can configure class policies for as many classes as are defined on the router, up to the maximum of 64. However, the total amount of bandwidth allocated for all classes included in a policy map must not exceed 75 percent of the available bandwidth on the interface. The other 25 percent is used for control and routing traffic. (To override the 75 percent limitation, use the max-reserved bandwidth command.) If not all of the bandwidth is allocated, the remaining bandwidth is proportionally allocated among the classes, based on their configured bandwidth.
To configure class policies in a policy map, perform the tasks in the following sections:
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Configuring Class Policy Using Tail Drop
To configure a policy map and create class policies that make up the service policy, use the first command in global configuration mode to specify the policy map name, then use the following commands in policy-map class configuration mode to configure policy for a standard class. To configure policy for the default class, see the section "Configuring the Class-Default Class Policy."
To configure policy for more than one class in the same policy map, repeat Step 2 through Step 4. Note that because this set of commands uses the queue-limit command, the policy map uses tail drop, not Weighted Random Early Detection (WRED) packet drop.
Configuring Class Policy Using WRED Packet Drop
To configure a policy map and create class policies comprising the service policy, use the first global configuration command to specify the policy map name, then use the following policy-map class configuration commands to configure policy for a standard class. To configure policy for the default class, see the section "Configuring the Class-Default Class Policy."
To configure policy for more than one class in the same policy map, repeat Step 2 through Step 5. Note that this set of commands uses WRED packet drop, not tail drop.
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Configuring the Class-Default Class Policy
The class-default class is used to classify traffic that does not fall into one of the defined classes. Once a packet is classified, all of the standard mechanisms that can be used to differentiate service among the classes apply. The class-default class was predefined when you created the policy map, but you must configure it. If no default class is configured, then by default the traffic that does not match any of the configured classes is flow classified and given best-effort treatment.
By default, the class-default class is defined as flow-based WFQ. However, configuring the default class with the bandwidth policy-map class configuration command disqualifies the default class as flow-based WFQ.
To configure a policy map and configure the class-default class to use tail drop, use the first global configuration command to specify the policy map name, then use the following policy-map class configuration commands to configure policy for the default class:
To configure a policy map and configure the class-default class to use WRED packet drop, use the first global configuration command to specify the policy map name, then use the following policy-map class configuration commands to configure policy for the default class:
Attaching the Service Policy and Enabling CBWFQ
To attach a service policy to the output interface and enable CBWFQ on the interface, use the following interface configuration command. When CBWFQ is enabled, all classes configured as part of the service policy map are installed in the fair queueing system.
Router(config-if)# service-policy output policy-map
Enables CBWFQ and attaches the specified service policy map to the output interface.
Configuring CBWFQ on a physical interface is only possible if the interface is in the default queueing mode. Serial interfaces at E1 (2.048 Mbps) and below use WFQ by default—other interfaces use FIFO by default. Enabling CBWFQ on a physical interface overrides the default interface queueing method. Enabling CBWFQ on an ATM PVC does not override the default queueing method.
Modifying the Bandwidth for an Existing Policy Map Class
To change the amount of bandwidth allocated for an existing class, use the following commands beginning in global configuration mode:
Modifying the Queue Limit for an Existing Policy Map Class
To change the maximum number of packets that can accrue in a queue reserved for an existing class, use the following commands beginning in global configuration mode:
Configuring the Bandwidth Limiting Factor
To change the maximum reserved bandwidth allocated for CBWFQ, LLQ, and the IP RTP Priority feature, use the following command in interface configuration mode:
Router(config-if)# max-reserved-bandwidth percent
Changes the maximum configurable bandwidth for CBWFQ, LLQ, and IP RTP Priority. The default is 75 percent.
Deleting Classes
To delete one or more class maps from a service policy map, use the following commands beginning in global configuration mode:
Deleting Policy Maps
To delete a policy map, use the following command in global configuration mode:
Router(config)# no policy-map policy-map
Specifies the name of the policy map to be deleted.
Verifying Configuration of Policy Maps and Their Classes
To display the contents of a specific policy map, a specific class from a specific policy map, or all policy maps configured on an interface, use one of the following commands in global configuration mode:
The counters displayed after issuing the show policy-map interface command are updated only if congestion is present on the interface.
IP RTP Priority Configuration Task List
To configure IP RTP Priority, perform the tasks in the following sections. The first task is required; the remaining tasks are optional.
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See the end of this chapter for the section "IP RTP Priority Configuration Examples."
Configuring IP RTP Priority
To reserve a strict priority queue for a set of RTP packet flows belonging to a range of UDP destination ports, use the following command in interface configuration mode:
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The ip rtp reserve and ip rtp priority commands cannot be configured on the same interface.
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Configuring the Bandwidth Limiting Factor
To change the maximum reserved bandwidth allocated for CBWFQ, LLQ, and the IP RTP Priority feature, use the following command in interface configuration mode:
Router(config-if)# max-reserved-bandwidth percent
Changes the maximum configurable bandwidth for CBWFQ, LLQ, and IP RTP Priority. The default is 75 percent.
Verifying IP RTP Priority
To see the contents of the priority queue (such as queue depth and the first packet queued), use the following command in EXEC mode:
Router# show queue interface-type interface-number
Displays queueing configuration and statistics for a particular interface.
Monitoring and Maintaining IP RTP Priority
To tune your RTP bandwidth or decrease RTP traffic if the priority queue is experiencing drops, use one or more of the following commands in EXEC mode:
Frame Relay IP RTP Priority Configuration Task List
To configure Frame Relay IP RTP Priority, perform the tasks in the following sections. The first task is required; the remaining tasks are optional.
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See the end of this chapter for the section "Frame Relay IP RTP Priority Configuration Examples."
Configuring Frame Relay IP RTP Priority
To reserve a strict priority queue on a Frame Relay PVC for a set of RTP packet flows belonging to a range of UDP destination ports, use the following command in map-class configuration mode:
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Verifying Frame Relay IP RTP Priority
To verify the Frame Relay IP RTP Priority feature, use one of the following commands in EXEC mode:
Monitoring and Maintaining Frame Relay IP RTP Priority
To tune your RTP bandwidth or decrease RTP traffic if the priority queue is experiencing drops, use the following command in EXEC mode:
Router# debug priority
Displays priority queueing output if packets are dropped from the priority queue.
Low Latency Queueing Configuration Task List
To configure low latency queueing, perform the tasks in the following sections. The first section is required; the remaining sections are optional.
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See the end of this chapter for the section "Low Latency Queueing Configuration Examples."
Configuring Low Latency Queueing
To give priority to a class within a policy map, use the following command in policy-map class configuration mode:
Router(config-pmap-c)# priority bandwidth
Reserves a strict priority queue for this class of traffic.
Configuring the Bandwidth Limiting Factor
To change the maximum reserved bandwidth allocated for CBWFQ, LLQ, and the IP RTP Priority feature, use the following command in interface configuration mode:
Router(config-if)# max-reserved-bandwidth percent
Changes the maximum configurable bandwidth for CBWFQ, LLQ, and IP RTP Priority. The default is 75 percent.
Verifying Low Latency Queueing
To see the contents of the priority queue (such as queue depth and the first packet queued), use the following command in EXEC mode:
Router# show queue interface-type interface-number
Displays queueing configuration and statistics for a particular interface.
The priority queue is the queue whose conversation ID is equal to the number of dynamic queues plus 8. The packets in the priority queue have a weight of 0.
Monitoring and Maintaining Low Latency Queueing
To tune your RTP bandwidth or decrease RTP traffic if the priority queue is experiencing drops, use one or more of the following commands in EXEC mode:
Flow-Based WFQ Configuration Examples
The following example requests a fair queue with a congestive discard threshold of 64 messages, 512 dynamic queues, and 18 RSVP queues:
Router(config)# interface Serial 3/0Router(config-if)# ip unnumbered Ethernet 0/0Router(config-if)# fair-queue 64 512 18For information on how to configure WFQ, see the section "Flow-Based Weighted Fair Queueing Configuration Task List" earlier in this chapter.
DWFQ Configuration Examples
The following examples provide DWFQ configuration examples:
For information on how to configure DWFQ, see the section "VIP-Distributed Weighted Fair Queueing Configuration Task List" earlier in this chapter.
Flow-Based DWFQ Example
The following example enables DWFQ on the HSSI 0/0/0 interface:
Router(config)# interface Hssi0/0/0Router(config-if)# description 45Mbps to R2Router(config-if)# ip address 200.200.14.250 255.255.255.252Router(config-if)# fair-queueThe following is sample output from the show interfaces fair-queue command for this configuration:
Router# show interfaces hssi 0/0/0 fair-queueHssi0/0/0 queue size 0packets output 35, drops 0WFQ: global queue limit 401, local queue limit 200QoS-Group-Based DWFQ Example
The following example configures QoS-group-based DWFQ. CAR policies are used to assign packets with an IP precedence of 2 to QoS group 2, and packets with IP precedence 6 are assigned to QoS group 6.
Router(config)# interface Hssi0/0/0Router(config-if)# ip address 188.1.3.70 255.255.255.0Router(config-if)# rate-limit output access-group rate-limit 6 155000000 2000000 8000000 conform-action set-qos-transmit 6 exceed-action dropRouter(config-if)# rate-limit output access-group rate-limit 2 155000000 2000000 8000000 conform-action set-qos-transmit 2 exceed-action dropRouter(config-if)# fair-queue qos-groupRouter(config-if)# fair-queue qos-group 2 weight 10Router(config-if)# fair-queue qos-group 2 limit 27Router(config-if)# fair-queue qos-group 6 weight 30Router(config-if)# fair-queue qos-group 6 limit 27!Router(config)# access-list rate-limit 2 2Router(config)# access-list rate-limit 6 6Use the show interfaces fair-queue command to view WFQ statistics.
Router# show interfaces fair-queueHssi0/0/0 queue size 0packets output 806232, drops 1WFQ: aggregate queue limit 54, individual queue limit 27max available buffers 54Class 0: weight 60 limit 27 qsize 0 packets output 654 drops 0Class 2: weight 10 limit 27 qsize 0 packets output 402789 drops 0Class 6: weight 30 limit 27 qsize 0 packets output 402789 drops 1ToS-Based DWFQ Example
The following example configures ToS-based DWFQ using the default parameters:
Router# configure terminalRouter(config)# interface Hssi0/0/0Router(config-if)# fair-queue tosRouter(config-if)# endThe following is output of the show running-config command for the Hssi0/0/0 interface. Notice that the router automatically adds the default weights and limits for the ToS classes to the configuration.
interface Hssi0/0/0ip address 188.1.3.70 255.255.255.0fair-queue tosfair-queue tos 1 weight 20fair-queue tos 1 limit 27fair-queue tos 2 weight 30fair-queue tos 2 limit 27fair-queue tos 3 weight 40fair-queue tos 3 limit 27Use the show interfaces fair-queue command to view DWFQ statistics.
Router# show interfaces fair-queueHssi0/0/0 queue size 0packets output 1417079, drops 2WFQ: aggregate queue limit 54, individual queue limit 27max available buffers 54Class 0: weight 10 limit 27 qsize 0 packets output 1150 drops 0Class 1: weight 20 limit 27 qsize 0 packets output 0 drops 0Class 2: weight 30 limit 27 qsize 0 packets output 775482 drops 1Class 3: weight 40 limit 27 qsize 0 packets output 0 drops 0CBWFQ Configuration Examples
The following sections provide CBWFQ configuration examples:
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For information on how to configure CBWFQ, see the section "Class-Based Weighted Fair Queueing Configuration Task List" earlier in this chapter.
Class Map Configuration Example
In the following example, ACLs 101 and 102 are created. Next, two class maps are created and their match criteria are defined. For the first map class, called class1, the numbered ACL 101 is used as the match criterion. For the second map class, called class2, the numbered ACL 102 is used as the match criterion. Packets are checked against the contents of these ACLs to determine if they belong to the class.
Router(config)# access-list 101 permit udp host 10.10.10.10 host 10.10.10.20 range 16384 20000Router(config)# access-list 102 permit udp host 10.10.10.10 host 10.10.10.20 range 53000 56000Router(config)# class-map class1Router(config-cmap)# match access-group 101Router(config-cmap)# exitRouter(config-cmap)# class-map class2Router(config-cmap)# match access-group 102Router(config-cmap)# exitPolicy Creation Example
In the following example, a policy map called policy1 is defined to contain policy specification for the two classes—class1 and class2. The match criteria for these classes were defined in the previous section "Class Map Configuration Example."
For class1, the policy specifies the bandwidth allocation request and the maximum number of packets that the queue for this class can accumulate. For class2, the policy specifies only the bandwidth allocation request, so the default queue limit of 64 packets is assumed.
Router(config)# policy-map policy1Router(config-pmap)# class class1Router(config-pmap-c)# bandwidth 3000Router(config-pmap-c)# queue-limit 30Router(config-pmap-c)# exitRouter(config-pmap)# class class2Router(config-pmap-c)# bandwidth 2000Router(config-pmap-c)# exitPolicy Attachment to Interfaces Example
The following example shows how to attach an existing policy map. After you define a policy map, you can attach it to one or more interfaces to specify the service policy for those interfaces. Although you can assign the same policy map to multiple interfaces, each interface can have only one policy map attached at the input and one policy map attached at the output.
The policy map in this example was defined in the previous section, "Policy Creation Example."
Router(config)# interface e1/1Router(config-if)# service output policy1Router(config-if)# exitRouter(config)# interface fa1/0/0Router(config-if)# service output policy1Router(config-if)# exitCBWFQ Using WRED Packet Drop Example
In the following example, the class map class1is created and defined to use the input interface FastEthernet0/1 as a match criterion to determine if packets belong to the class. Next, the policy map policy1 is defined to contain policy specification for class1, which is configured for WRED packet drop.
Router(config)# class-map class1Router(config-cmap)# match input-interface FastEthernet0/1!Router(config)# policy-map policy1Router(config-pmap)# class class1Router(config-pmap-c)# bandwidth 1000Router(config-pmap-c)# random-detect!Router(config)# interface serial0/0Router(config-if)# service-policy output policy1
