Table Of Contents
Configuring Weighted Fair Queueing
Flow-Based Weighted Fair Queueing Configuration Task List
Distributed Weighted Fair Queueing Configuration Task List
Configuring QoS-Group-Based DWFQ
Configuring Type of Service-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
Distributed Class-Based Weighted Fair Queueing Configuration Task List
Modifying the Bandwidth for an Existing Traffic Class
Modifying the Queue Limit for an Existing Traffic Class
Monitoring and Maintaining DCBWFQ
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
Frame Relay PVC Interface Priority Configuration Task List
Configuring PVC Priority in a Map Class
Enabling Frame Relay PIPQ and Setting Queue Limits
Assigning a Map Class to a PVC
Monitoring and Maintaining Frame Relay PIPQ
Low Latency Queueing Configuration Task List
Configuring the Bandwidth Limiting Factor
Monitoring and Maintaining LLQ
Distributed LLQ Configuration Task List
Configuring a Priority Queue for an Amount of Available Bandwidth
Configuring a Priority Queue for a Percentage of Available Bandwidth
Configuring a Transmission Ring Limit
Verifying a Transmission Ring Limit
Monitoring and Maintaining Distributed LLQ
Low Latency Queueing for Frame Relay Configuration Task List
Configuring Class Policy in the Policy Map
Configuring Class Policy for a LLQ Priority Queue
Configuring Class Policy Using a Specified Bandwidth and WRED Packet Drop
Configuring the Class-Default Class Policy
Attaching the Service Policy and Enabling LLQ for Frame Relay
Verifying Configuration of Policy Maps and Their Classes
Monitoring and Maintaining LLQ for Frame Relay
Configuring Burst Size in LLQ Configuration Task List
Configuring the LLQ Burst Size
Per-VC Hold Queue Support for ATM Adapters Configuration Task List
Configuring the per-VC Hold Queue on an ATM Adapter
Verifying the Configuration of the per-VC Hold Queue on an ATM Adapter
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
All Classes for a Specified Service Policy Map
All Classes for All Service Policy Maps
Specified Class for a Service Policy Map
All Classes for All Service Policy Maps on a Specified Interface
Distributed CBWFQ Configuration Examples
Traffic Class Configuration Example
Traffic Policy Creation Example
Traffic Policy Attachment to an Interface Example
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
Frame Relay PVC Interface PQ Configuration Examples
Virtual Template Configuration Example
Multilink Bundle Configuration Example
Distributed LLQ Configuration Examples
Enabling PQ for an Amount of Available Bandwidth on an ATM Subinterface Example
Enabling PQ for a Percentage of Available Bandwidth on an ATM Subinterface Example
Limiting the Transmission Ring Limit on an ATM Interface Example
Limiting the Transmission Ring Limit on an ATM PVC Subinterface Example
LLQ for Frame Relay Configuration Examples
Burst Size in LLQ Configuration Examples
Per-VC Hold Queue Support for ATM Adapters Examples
Configuring Weighted Fair Queueing
This chapter describes the tasks for configuring flow-based weighted fair queueing (WFQ), distributed WFQ (DWFQ), and class-based WFQ (CBWFQ), and distributed class-based WFQ (DCBWFQ) and the related features described in the following section, which provide strict priority queueing (PQ) 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.
To identify the hardware platform or software image information associated with a feature, use the Feature Navigator on Cisco.com to search for information about the feature or refer to the software release notes for a specific release. For more information, see the "Identifying Supported Platforms" section in the "Using Cisco IOS Software" chapter in this book.
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. 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 described in the following sections. The task in the first section is required; the task in the remaining 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 WFQ 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 WFQ.
Flow-based WFQ uses a traffic data stream discrimination registry service to determine to which traffic stream a message belongs. Refer to 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. Refer to 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 the following commands in EXEC mode, as needed:
Distributed Weighted Fair Queueing Configuration Task List
To configure DWFQ, perform one of the mutually exclusive tasks described in the following sections:
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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 an RSP-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.
See the end of this chapter for the section "DWFQ Configuration Examples."
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 Type of Service-Based DWFQ
To configure type of service (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 the following commands in EXEC mode, as needed:
Router# show interfaces [interface]
Displays the 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 described in the following sections. The tasks in the first three sections are required; the tasks in 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."
For information on how to configure per-VC WFQ and CBWFQ, see the chapter "Configuring IP to ATM Class of Service" in this book.
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 use one of the following commands in class-map configuration mode, as needed:
Other match criteria can be used when defining class maps. For additional match criteria, see the section "Creating a Traffic Class" in the chapter "Configuring the Modular Quality of Service Command-Line Interface" in this book.
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 optional tasks described in the following sections. If you do not perform the steps in these sections, the default actions are used.
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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, as needed, to configure policy for a standard class. To configure policy for the default class, see the section "Configuring the Class-Default Class Policy" in this chapter.
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 command in global configuration mode, as needed, to specify the policy map name, then use the following commands in policy-map class configuration mode, as needed, to configure policy for a standard class. To configure policy for the default class, see the section "Configuring the Class-Default Class Policy" in this chapter.
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 command in global configuration mode to specify the policy map name, then to configure policy for the default class use the following commands in policy-map class configuration mode:
To configure a policy map and configure the class-default class to use WRED packet drop, use the first command in global configuration mode to specify the policy map name, then to configure policy for the default class use the following commands in policy-map class configuration mode:
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 command in interface configuration mode. 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 permanent virtual circuit (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 Resource Reservation Protocol (RSVP), CBWFQ, LLQ, IP RTP Priority, Frame Relay IP RTP Priority, and Frame Relay PVC Interface Priority Queueing (PIPQ), use the following command in interface configuration mode:
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 the following commands in EXEC mode, as needed:
The counters displayed after issuing the show policy-map interface command are updated only if congestion is present on the interface.
Distributed Class-Based Weighted Fair Queueing Configuration Task List
To configure DCBWFQ, perform the tasks described in the following sections. Although all the tasks are listed as optional, you must complete the task in either the first or second section.
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DCBWFQ is configured using user-defined traffic classes and service policies. Traffic classes and service policies are configured using the Modular Quality of Service Command-Line Interface (CLI) feature. For information on how to configure QoS with the Modular QoS CLI, see the chapter "Configuring the Modular Quality of Service Command-Line Interface" in this book.
See the end of this chapter for the section "Verifying Configuration of Policy Maps and Their Classes."
Modifying the Bandwidth for an Existing Traffic Class
To change the amount of bandwidth allocated for an existing traffic class in congested environments, use the following commands beginning in global configuration mode:
After configuring the traffic policy with the policy-map command, you must still attach the traffic policy to an interface before it is successfully enabled. For information on attaching a traffic policy to an interface, see the chapter "Configuring the Modular Quality of Service Command-Line Interface" in this book.
Modifying the Queue Limit for an Existing Traffic Class
To change the maximum number of packets that can accrue in a queue reserved for an existing traffic class, use the following commands beginning in global configuration mode:
After configuring the service policy with the policy-map command, you must still attach the traffic policy to an interface before it is successfully enabled. For information on attaching a traffic policy to an interface, see the chapter "Configuring the Modular Quality of Service Command-Line Interface" in this book.
Monitoring and Maintaining DCBWFQ
To display the configuration of a traffic policy and its associated traffic classes, use the following commands in EXEC mode, as needed:
IP RTP Priority Configuration Task List
To configure IP RTP Priority, perform the tasks described in the following sections. The task in the first section is required; the tasks in the remaining sections are optional.
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See the end of this chapter for the section "IP RTP Priority Configuration Examples."
Frame Relay Traffic Shaping (FRTS) and Frame Relay Fragmentation (FRF.12) must be configured before the Frame Relay IP RTP Priority feature is used. For information about configuring FRTS and FRF.12, refer to the Cisco IOS Wide-Area Networking Configuration Guide.
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.
The frame-relay ip rtp priority command provides strict PQ for Frame Relay PVCs. For more information about this command, refer to the Cisco IOS Quality of Service Solutions Command Reference.
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 display 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 the following commands in EXEC mode, as needed:
Frame Relay IP RTP Priority Configuration Task List
To configure Frame Relay IP RTP Priority, perform the tasks described in the following sections. The task in the first section is required; the tasks in the remaining sections 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 the following commands in EXEC mode, as needed:
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.
Frame Relay PVC Interface Priority Configuration Task List
To configure the Frame Relay PVC Interface Priority feature, perform the tasks described in the following sections. The tasks in the first three sections are required; the tasks in the remaining sections are optional.
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See the end of this chapter for the section "Frame Relay PVC Interface PQ Configuration Examples."
Configuring PVC Priority in a Map Class
To configure PVC priority within a map class, use the following commands beginning in global configuration mode:
Enabling Frame Relay PIPQ and Setting Queue Limits
To enable Frame Relay (FR) PIPQ and set the priority queue sizes, use the following commands beginning in global configuration mode:
Assigning a Map Class to a PVC
To assign a map class to a specific PVC, use the following commands beginning in interface configuration mode:
Verifying Frame Relay PIPQ
To verify the configuration of Frame Relay (FR) PIPQ, use the following commands in privileged EXEC mode, as needed:
Monitoring and Maintaining Frame Relay PIPQ
To monitor and maintain Frame Relay (FR) PIPQ, use the following commands in privileged EXEC mode, as needed:
