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Cisco IOS Quality of Service Solutions Command Reference, Release 12.1
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About the Cisco IOS Software Documentation
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Using Cisco IOS Software
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Commands: access-list rate-limit -- frame-relay ip rtp priority
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Commands: ip rsvp atm-peak-rate-limit -- ip rtp priority
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Commands: match access-group -- pvc-bundle
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Commands: queue-limit -- set ip precedence
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Commands: show access-lists rate-limit -- traffic-shape rate
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Index
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Table Of Contents
exponential-weighting-constant
Quality of Service Commands
Use the commands in this chapter to configure quality of service (QoS), a measure of performance for a transmission system that reflects its transmission quality and service availability. The commands are arranged alphabetically.
For QoS configuration information and examples, refer to the Cisco IOS Quality of Service Solutions Configuration Guide.
access-list rate-limit
To configure an access list for use with committed access rate (CAR) policies, use the access-list rate-limit global configuration command. To remove the access list from the configuration, use the no form of this command.
access-list rate-limit acl-index {precedence | mac-address | mask prec-mask}
no access-list rate-limit acl-index {precedence | mac-address | mask prec-mask}
Syntax Description
Defaults
No CAR access lists are configured.
Command Modes
Global configuration
Command History
Usage Guidelines
This command classifies packets by the specified IP Precedence or MAC address for a particular CAR access list. You can then apply CAR policies, using the rate-limit command, to individual rate-limit access lists. Thus, packets with different IP Precedences or MAC addresses are treated differently by the CAR process.
You can specify only one command for each rate-limit access list. If you enter this command multiple times with the same access list number, the new command will overwrite the previous command.
Use the mask keyword to assign multiple IP Precedences to the same rate-limit access list. To determine the mask value, perform the following steps:
Step 1
Decide which precedences you want to assign to this rate-limit access list.
Step 2
Step 3
Step 4
A mask of FF matches any precedence, and 00 does not match any precedence.
Examples
The following example assigns any packets with a MAC address of 00e0.34b0.7777 to rate-limit access list 100:
access-list rate-limit 100 00e0.34b0.7777The following example assigns packets with an IP Precedence of 0, 1, or 2 to the rate-limit access list 25:
access-list rate-limit 25 mask 07Related Commands
show access-lists rate-limit
Displays information about rate-limit access lists.
show ip cef
Displays entries in the FIB that are unresolved or displays a FIB summary.
bandwidth (policy-map class)
To specify or modify the bandwidth allocated for a class belonging to a policy map, use the bandwidth policy-map class configuration command. To remove the bandwidth specified for a class, use the no form of this command.
bandwidth {bandwidth-kbps | percent percent}
no bandwidth {bandwidth-kbps | percent percent}
Syntax Description
bandwidth-kbps
Amount of bandwidth (in kbps) to be assigned to the class.
percent percent
Percentage of available bandwidth to be assigned to the class.
Defaults
No default behavior.
Command Modes
Policy-map class configuration
Command History
Usage Guidelines
You use the bandwidth command when you configure a policy map for a class defined by the class-map command. The bandwidth command specifies the bandwidth for traffic in that class. Class-based weighted fair queueing (CBWFQ) derives the weight for packets belonging to the class from the bandwidth allocated to the class. CBWFQ then uses the weight to ensure that the queue for the class is serviced fairly.
Besides specifying the amount of bandwidth in kbps, you can assign bandwidth as a percentage of the available bandwidth. During periods of congestion, the classes are serviced in proportion to their configured bandwidth percentages. Available bandwidth is equal to the interface bandwidth minus the sum of all bandwidths reserved by Resource Reservation Protocol (RSVP), IP RTP Priority, and low latency queueing (LLQ).
Note
Configuring bandwidth in percentages is most useful when the underlying link bandwidth is unknown or the relative class bandwidth distributions are known. For interfaces that have adaptive shaping rates (such as available bit rate [ABR] virtual circuits), CBWFQ can be configured by configuring class bandwidths in percentages.
The following restrictions apply to the bandwidth command:
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For more information on bandwidth allocation, refer to the chapter "Congestion Management Overview" in the Cisco IOS Quality of Service Solutions Configuration Guide.
Note that when the policy map containing class policy configurations is attached to the interface to stipulate the service policy for that interface, available bandwidth is assessed. If a policy map cannot be attached to a particular interface because of insufficient interface bandwidth, then the policy is removed from all interfaces to which it was successfully attached.
Examples
The following example modifies the bandwidth for a class called acl22. The default class belongs to a service policy map called polmap6.
policy-map polmap6class acl22bandwidth 2000queue-limit 30CBWFQ Bandwidth Guarantee
The following example illustrates how bandwidth is guaranteed when only CBWFQ is configured:
! The following commands create a policy map with two classes:policy-map policy1class class1bandwidth percent 50exitclass class2bandwidth percent 25exitend!The following commands attach the policy to interface s3/2:interface s3/2service output policy1endThe following output from the show policy-map interface command shows that 50 percent of the interface bandwidth is guaranteed for class1 and 25 percent is guaranteed for class2:
Router# show policy-map interface s3/2Serial3/2 output :policy1Class class1Weighted Fair QueueingOutput Queue:Conversation 265Bandwidth 50 (%) Packets Matched 0 Max Threshold 64 (packets)(discards/tail drops) 0/0Class class2Weighted Fair QueueingOutput Queue:Conversation 266Bandwidth 25 (%) Packets Matched 0 Max Threshold 64 (packets)(discards/tail drops) 0/0In this example, the entire interface bandwidth is available for CBWFQ because RSVP, IP RTP Priority, and LLQ are not enabled. If this policy map is attached to a physical interface, the available bandwidth is equal to the link bandwidth. During periods of congestion, 50 percent of the link bandwidth is guaranteed to class1 and 25 percent of the link bandwidth is guaranteed to class2. For example, if this policy map was attached to a 1 Mbps link, class1 would be guaranteed 500 kbps and class2 would be guaranteed 250 kbps during periods of congestion.
CBWFQ and LLQ Bandwidth Allocation
This example illustrates how bandwidth is guaranteed if LLQ is configured with CBWFQ. Remember, the available bandwidth for CBWFQ is the link bandwidth minus the sum of the bandwidths reserved by RSVP, LLQ, and IP RTP Priority.
In this example, LLQ is enabled in a third class called voice1:
! The following commands create a policy map with three classes:policy map policy1class class1bandwidth percent 50exitclass class2bandwidth percent 25exitendclass voice1priority 500exitend!The following commands attach the policy to interface s3/2:interface s3/2service output policy1endThe following output from the show policy-map command shows that 50 percent of the interface bandwidth is guaranteed for class1, 25 percent is guaranteed for class2, and 500 kbps is guaranteed for voice1:
Router# show policy-map policy1Policy Map policy1Class class1Weighted Fair QueueingBandwidth 50 (%) Max Threshold 64 (packets)Class class2Weighted Fair QueueingBandwidth 25 (%) Max Threshold 64 (packets)Class voice1Weighted Fair QueueingStrict PriorityBandwidth 500 (kbps) Max Threshold 64 (packets)Because LLQ reserved 500 kbps of the interface bandwidth, if you attach this policy map to an interface with 2 Mbps, only 1.5 Mbps is available for CBWFQ classes. In this example, 50 percent of 1.5 Mbps (750 kbps) is guaranteed for class1 and 25 percent (375 kbps) is guaranteed for class2. The remaining 25 percent of the available bandwidth (375 kbps) is shared by class1, class2, and any best-effort traffic.
Related Commands
bgp-policy
To enable the Policy Propagation via Border Gateway Protocol (BGP) feature on the interface, use the bgp-policy interface configuration command. To disable the Policy Propagation via BGP feature, use the no form of this command.
bgp-policy ip-prec-map
no bgp-policy ip-prec-map
Syntax Description
Defaults
The Policy Propagation via BGP feature is disabled.
Command Modes
Interface configuration
Command History
Usage Guidelines
For the Policy Propagation via BGP feature to work, you must enable BGP and either Cisco Express Forwarding (CEF) or distributed CEF (dCEF). In addition, the proper route-map configuration must be in place to specify the IP Precedence (for example, the set ip precedence route-map configuration command).
Note
To display QoS policy information for the interface, use the show ip interface command.
Examples
The following example enables the Policy Propagation via BGP feature on an interface based on the source address and the IP Precedence setting:
configure terminalinterface ethernet 4/0/0bgp-policy ip-prec-mapendbump
To configure the bumping rules for a virtual circuit (VC) class that can be assigned to a VC bundle, use the bump vc-class configuration command. To remove the explicit bumping rules for the VCs assigned this class and default them to implicit bumping, use the no bump explicit command. To specify that the VC bundle members do not accept any bumped traffic, use the no bump traffic command.
To configure the bumping rules for a specific VC member of a bundle, use the bump bundle-vc configuration command. To remove the explicit bumping rules for the VC and default it to implicit bumping, use the no bump explicit command. To specify that the VC does not accept any bumped traffic, use the no form of this command.
bump {implicit | explicit precedence-level | traffic}
no bump {explicit precedence-level | traffic}
Syntax Description
Defaults
Implicit bumping.
Bump traffic (VCs accept bumped traffic).
Command Modes
VC-class configuration (for a VC class).
Bundle-vc configuration (for a VC bundle member).
Command History
Usage Guidelines
Use the bump command in bundle-vc configuration mode to configure bumping rules for a discrete VC bundle member or in vc-class configuration mode to configure a VC class that can be assigned to a bundle member.
The effects of different bumping configuration approaches are as follows:
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Note
To use this command in vc-class configuration mode, you must enter the vc-class atm global configuration command before you enter this command.
To use this command to configure an individual bundle member in bundle-vc configuration mode, first enter the bundle command to enact bundle configuration mode for the bundle to which you want to add or modify the VC member to be configured. Then, use the pvc-bundle command to specify the VC to be created or modified and enter bundle-vc configuration mode.
This command has no effect if the VC class that contains the command is attached to a standalone VC, that is, if the VC is not a bundle member. In this case, the attributes are ignored by the VC.
VCs in a VC bundle are subject to the following configuration inheritance rules (listed in order of next highest precedence):
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Examples
The following example configures the class premium-class to define parameters applicable to a VC in a bundle. Unless overridden with a bundle-vc bump configuration, the VC that uses this class will not allow other traffic to be bumped onto it.
vc-class atm premium-classno bump traffic bump explicitly 7Related Commands
bundle
To create a bundle or modify an existing bundle to enter bundle configuration mode, use the bundle subinterface configuration command. To remove the specified bundle, use the no form of this command.
bundle bundle-name
no bundle bundle-name
Syntax Description
Defaults
None
Command Modes
Subinterface configuration
Command History
Usage Guidelines
From within bundle configuration mode you can configure the characteristics and attributes of the bundle and its members, such as the encapsulation type for all virtual circuits (VCs) in the bundle, the bundle management parameters, the service type, and so on. Attributes and parameters you configure in bundle configuration mode are applied to all VC members of the bundle.
VCs in a VC bundle are subject to the following configuration inheritance rules (listed in order of next highest precedence):
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To display status on bundles, use the show atm bundle and show atm bundle statistics commands.
Examples
The following example configures a bundle called new-york. The example specifies the IP address of the subinterface and the router protocol—the router uses IS-IS as an IP routing protocol—then configures the bundle.
interface a1/0.1 multipoint ip address 10.0.0.1 255.255.255.0 ip router isis bundle new-yorkRelated Commands
class (policy-map)
To specify the name of the class whose policy you want to create or change or to specify the default class (commonly known as the class-default class) before you configure its policy, use the class policy-map configuration command. To remove a class from the policy map, use the no form of this command.
class {class-name | class-default}
no class {class-name | class-default}
Syntax Description
class-name
The name of the class for which you want to configure or modify policy.
class-default
Specifies the default class so that you can configure or modify its policy.
Defaults
No default behavior.
Command Modes
Policy-map configuration
Command History
Usage Guidelines
Enter the policy-map command to identify the policy map and enter policy map configuration mode before you use the class command. After you specify a policy map, you can configure policy for new classes or modify policy for any existing classes in that policy map.
The class name that you specify in the policy map ties the characteristics for that class—that is, its policy—to the class map and its match criteria, as configured using the class-map command.
When you configure policy for a class and specify its bandwidth and attach the policy map to an interface, class-based weighted fair queueing (CBWFQ) determines if the bandwidth requirement of the class can be satisfied. If so, CBWFQ creates the necessary internal data structures to maintain state for the class and allocates a queue for it.
When a class is removed, available bandwidth for the interface is incremented by the amount previously allocated to the class.
The maximum number of classes you can configure for a router—and, therefore, within a policy map—is 64.
The predefined default class called class-default 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 define a class policy to use either tail drop (by using the queue-limit command) or Weighted Random Early Detection (WRED) packet drop (by using the random-detect command). You cannot use the queue-limit and random-detect commands in the same class policy, but they can be used in two class policies in the same policy map.
You can configure the bandwidth command when either the queue-limit or the random-detect command is configured in a class policy. The bandwidth command specifies the amount of bandwidth allocated for the class.
For the default class, you can configure the fair-queue (class-default) command. The fair-queue command specifies the number of dynamic queues for the default class. The fair-queue command can be used in the same class policy as either the queue-limit or random-detect command. It cannot be used with the bandwidth command.
Examples
The following example configures three class policies included in the policy map called policy1. Class1 specifies policy for traffic that matches access control list 136. Class2 specifies policy for traffic on the interface ethernet101. The third class is the default class to which packets that do not satisfy configured match criteria are directed.
! The following commands create class-maps class1 and class2! and define their match criteria:class-map class1match access-group 136class-map class2match input-interface ethernet101! The following commands create the policy map, which is defined to contain policy! specification for class1, class2, and the default class:policy-map policy1class class1bandwidth 2000queue-limit 40class class2bandwidth 3000random-detectrandom-detect exponential-weighting-constant 10class class-defaultfair-queue 16queue-limit 20Class1 has these characteristics: A minimum of 2000 kbps of bandwidth are expected to be delivered to this class in the event of congestion, and the queue reserved for this class can enqueue 40 packets before tail drop is enacted.
Class2 has these characteristics: A minimum of 3000 kbps of bandwidth are expected to be delivered to this class in the event of congestion, and a weight factor of 10 is used to calculate the average queue size. For congestion avoidance, WRED packet drop is used, not tail drop.
The default class has these characteristics: 16 dynamic queues are reserved for traffic that does not meet the match criteria of other classes whose policy is defined by the policy map policy1, and a maximum of 20 packets per queue are enqueued before tail drop is enacted to handle additional packets.
Note
The following example configures policy for the default class included in the policy map called policy2. The default class has these characteristics: 20 dynamic queues are available for traffic that does not meet the match criteria of other classes whose policy is defined by the policy map policy2, and a weight factor of 14 is used to calculate the average queue size. For congestion avoidance, WRED packet drop is used, not tail drop.
policy-map policy2class class-defaultfair-queue 20random-detectrandom-detect exponential-weighting-constant 14Related Commands
class-bundle
To configure a virtual circuit (VC) bundle with the bundle-level commands contained in the specified VC class, use the class-bundle bundle configuration command. The no form of this command removes the VC class parameters from a VC bundle.
class-bundle vc-class-name
no class-bundle vc-class-name
Syntax Description
Defaults
No VC class is assigned to the VC bundle.
Command Modes
Bundle configuration
Command History
12.0 T
This command was introduced, replacing the class command for configuring ATM VC bundles.
Usage Guidelines
To use this command, you must first enter the bundle command to create the bundle and enter bundle configuration mode.
Use this command to assign a previously defined set of parameters (defined in a VC class) to an ATM VC bundle. Parameters set through bundle-level commands contained in a VC class are applied to the bundle and its VC members.
You can add the following commands to a VC class to be used to configure a VC bundle: oam-bundle, broadcast, encapsulation, protocol, oam retry, and inarp.
Bundle-level parameters applied through commands configured directly on a bundle supersede bundle-level parameters applied through a VC class by the class-bundle command. Some bundle-level parameters applied through a VC class or directly to the bundle can be superseded by commands that you directly apply to individual VCs in bundle-vc configuration mode.
Examples
In the following example, a class called class1 is first created and then applied to the bundle called bundle1:
! The following commands create the class class1:vc-class atm class1encapsulation aal5snapbroadcastprotocol ip inarpoam-bundle manage 3oam 4 3 10! The following commands apply class1 to the bundle called bundle1:bundle bundle1class-bundle class1Taking into account hierarchy precedence rules, VCs belonging to the bundle1 bundle will be characterized by these parameters: aal5snap, encapsulation, broadcast on, use of Inverse Address Resolution Protocol (ARP) to resolve IP addresses, and Operation, Administration, and Maintenance (OAM) enabled.
Related Commands
class-map
To create a class map to be used for matching packets to the class whose name you specify, use the class-map global configuration command. To remove an existing class map from the router, use the no form of this command.
class-map [match-all | match-any] class-map-name
no class-map [match-all | match-any] class-map-name
Syntax Description
Defaults
No default behavior.
Command Modes
Global configuration
Command History
Usage Guidelines
Use this command to specify the name of the class for which you want to create or modify class map match criteria. Use of the class-map command enables class-map configuration mode in which you can enter one of the match commands to configure the match criteria for this class. Packets arriving at the output interface are checked against the match criteria configured for a class map to determine if the packet belongs to that class.
You can use one of the following commands in a class map:
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If you specify more than one command in the class map, only the last command entered applies. The last command overrides the previously entered commands.
Examples
The following example specifies class101 as the name of a class, and it defines a class map for this class. The class101 class specifies policy for traffic that matches access control list 101.
class-map class101match access-group 101Related Commands
clear ip rsvp reservation
To remove Resource Reservation Protocol (RSVP) RESV-related receiver information currently in the database, use the clear ip rsvp reservation command in EXEC mode.
clear ip rsvp reservation {session-ip-address sender-ip-address {tcp | udp | ip-protocol} session-dport sender-sport | *}
Syntax Description
Command Modes
EXEC
Command History
Usage Guidelines
Use the clear ip rsvp reservation command to remove the RESV-related sender information currently in the database so that when reservation requests arrive, based on the RSVP admission policy, the relevant ones can be reestablished.
Whenever you change the clockrate or bandwidth of an interface, RSVP does not update its database to reflect the change. This is because such a change requires that RSVP reestablish reservations based on the new clockrate or bandwidth value and arbitrarily dropping some reservations while retaining others is not desired. The solution is to clear the RESV state by issuing the clear ip rsvp reservation command.
The clear ip rsvp reservation command clears the RESV state from the router on which you issued the command and causes the router to send a PATH TEAR message to the upstream routers thereby clearing the RESV state for that reservation on all the upstream routers.
Examples
The following example clears all the RESV-related receiver information currently in the database:
Router# clear ip rsvp reservation *
The following example clears all the RESV-related receiver information for a specified reservation currently in the database:
Router# clear ip rsvp reservation 10.2.1.1 10.1.1.2 udp 10 20
Related Commands
clear ip rsvp sender
Removes RSVP PATH-related sender information currently in the database.
clear ip rsvp sender
To remove Resource Reservation Protocol (RSVP) PATH-related sender information currently in the database, use the clear ip rsvp sender command in EXEC mode.
clear ip rsvp sender {session-ip-address sender-ip-address {tcp | udp | ip-protocol} session-dport sender-sport | *}
Syntax Description
Command Modes
EXEC
Command History
Usage Guidelines
Use the clear ip rsvp sender command to remove the PATH-related sender information currently in the database so that when reservation requests arrive, based on the RSVP admission policy, the relevant ones can be reestablished.
Whenever you change the clockrate or bandwidth of an interface, RSVP does not update its database to reflect the change. This is because such a change requires that RSVP reestablish reservations based on the new clockrate or bandwidth value and arbitrarily dropping some reservations while retaining others is not desired. The solution is to clear the PATH state by issuing the clear ip rsvp sender command.
The clear ip rsvp sender command clears the PATH state from the router on which you issued the command and causes the router to send a PATH TEAR message to the downstream routers thereby clearing the PATH state for that reservation on all the downstream routers.
Examples
The following example clears all the PATH-related sender information currently in the database:
Router# clear ip rsvp sender *
The following example clears all the PATH-related sender information for a specified reservation currently in the database:
Router# clear ip rsvp sender 10.2.1.1 10.1.1.2 udp 10 20
Related Commands
clear ip rsvp reservation
Removes RSVP RESV-related receiver information currently in the database.
custom-queue-list
To assign a custom queue list to an interface, use the custom-queue-list interface configuration command. To remove a specific list or all list assignments, use the no form of this command.
custom-queue-list list
no custom-queue-list [list]
Syntax Description
Defaults
No custom queue list is assigned.
Command Modes
Interface configuration
Command History
Usage Guidelines
Only one queue list can be assigned per interface. Use this command in place of the priority-list command (not in addition to it). Custom queueing allows a fairness not provided with priority queueing. With custom queueing, you can control the bandwidth available on the interface when the interface is unable to accommodate the aggregate traffic enqueued. Associated with each output queue is a configurable byte count, which specifies how many bytes of data should be delivered from the current queue by the system before the system moves on to the next queue. When a particular queue is being processed, packets are sent until the number of bytes sent exceeds the queue byte count or until the queue is empty.
Use the show queueing custom and show interfaces commands to display the current status of the custom output queues.
Examples
In the following example, custom queue list number 3 is assigned to serial interface 0:
interface serial 0custom-queue-list 3Related Commands
exponential-weighting-constant
To configure the exponential weight factor for the average queue size calculation for a Weighted Random Early Detection (WRED) parameter group, use the exponential-weighting-constant random-detect-group configuration command. To return the exponential weight factor for the group to the default, use the no form of this command.
exponential-weighting-constant exponent
no exponential-weighting-constant
Syntax Description
Defaults
The weight factor is 9.
Command Modes
Random-detect-group configuration
Command History
Usage Guidelines
When used, this command is issued after the random-detect-group command is entered.
Use this command to change the exponent used in the average queue size calculation for a WRED parameter group. The average queue size is based on the previous average and the current size of the queue. The formula is:
average = (old_average * (1-1/2^x)) + (current_queue_size * 1/2^x)where x is the exponential weight factor specified in this command. Thus, the higher the factor, the more dependent the average is on the previous average.
Note
For high values of x, the previous average becomes more important. A large factor smooths out the peaks and lows in queue length. The average queue size is unlikely to change very quickly. The WRED process will be slow to start dropping packets, but it may continue dropping packets for a time after the actual queue size has fallen below the minimum threshold. The resulting slow-moving average will accommodate temporary bursts in traffic.
If the value of x gets too high, WRED will not react to congestion. Packets will be sent or dropped as if WRED were not in effect.
For low values of x, the average queue size closely tracks the current queue size. The resulting average may fluctuate with changes in the traffic levels. In this case, the WRED process will respond quickly to long queues. Once the queue falls below the minimum threshold, the process will stop dropping packets.
If the value of x gets too low, WRED will overreact to temporary traffic bursts and drop traffic unnecessarily.
Examples
The following example configures the WRED group sanjose with a weight factor of 10:
random-detect-group sanjoseexponential-weighting-constant 10Related Commands
fair-queue (class-default)
To specify the number of dynamic queues to be reserved for use by the class-default class as part of the default class policy, use the fair-queue policy-map class configuration command. To delete the configured number of dynamic queues from the class-default policy, use the no form of this command.
fair-queue [number-of-dynamic-queues]
no fair-queue [number-of-dynamic-queues]
Syntax Description
number-of-dynamic-queues
(Optional) A power of 2 number in the range of 16 to 4096 specifying the number of dynamic queues.
Defaults
The number of dynamic queues is derived from the interface or ATM permanent virtual circuit (PVC) bandwidth. See Table 3 for the default number of dynamic queues that weighted fair queueing (WFQ) and class-based WFQ (CBWFQ) use when they are enabled on an interface. See Table 4 for the default number of dynamic queues used when WFQ or CBWFQ is enabled on an ATM PVC.
Command Modes
Policy-map class configuration
Command History
Usage Guidelines
This command can be used for the default class (commonly known as the class-default class) only. You can use it in conjunction with either the queue-limit command or the random-detect command.
The class-default class is the default 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.
Examples
The following example configures policy for the default class included in the policy map called policy9. Packets that do not satisfy match criteria specified for other classes whose policies are configured in the same service policy are directed to the default class, for which 16 dynamic queues have been reserved. Because the queue-limit command is configured, tail drop is used for each dynamic queue when the maximum number of packets are enqueued and additional packets arrive.
policy-map policy9class class-defaultfair-queue 16queue-limit 20The following example configures policy for the default class included in the policy map called policy8. The fair-queue command reserves 20 dynamic queues to be used for the default class. For congestion avoidance, Weighted Random Early Detection (WRED) packet drop is used, not tail drop.
policy-map policy8class class-defaultfair-queue 20random-detectRelated Commands
queue-limit
Specifies or modifies the maximum number of packets the queue can hold for a class policy configured in a policy map.
random-detect (interface)
Enables WRED or DWRED.
fair-queue (DWFQ)
To enable VIP-Distributed weighted fair queueing (DWFQ), use the fair-queue interface configuration command. The command enables DWFQ on an interface using a VIP2-40 or greater interface processor. To disable DWFQ, use the no form of this command.
fair-queue
no fair-queue
Syntax Description
This command has no arguments or keywords.
Defaults
DWFQ is enabled by default for physical interfaces whose bandwidth is less than or equal to 2.048 Mbps.
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 Multilink PPP.
Table 5 lists the default queue lengths and thresholds.
Table 5 Default Fair Queue Lengths and Thresholds
Congestive discard threshold
64 messages
Dynamic queues
256 queues
Reservable queues
0 queues
Command Modes
Interface configuration
Command History
Usage Guidelines
With DWFQ, packets are classified by flow. Packets with the same source IP address, destination IP address, source TCP or User Datagram Protocol (UDP) port, destination TCP or UDP port, and protocol belong to the same flow.
DWFQ allocates an equal share of the bandwidth to each flow.
Examples
The following example enables DWFQ on the High-Speed Serial Interface (HSSI) 0/0/0 interface:
interface Hssi0/0/0description 45Mbps to R2ip address 10.200.14.250 255.255.255.252fair-queueRelated Commands
fair-queue (WFQ)
To enable weighted fair queueing (WFQ) for an interface, use the fair-queue interface configuration command. To disable weighted fair queueing for an interface, use the no form of this command.
fair-queue [congestive-discard-threshold [dynamic-queues [reservable-queues]]]
no fair-queue
Syntax Description
congestive-discard-threshold
(Optional) Number of messages allowed in each queue. The default is 64 messages, and a new threshold must be a power of 2 in the range 16 to 4096. When a conversation reaches this threshold, new message packets are discarded.
dynamic-queues
(Optional) Number of dynamic queues used for best-effort conversations (that is, a normal conversation not requiring any special network services). Values are 16, 32, 64, 128, 256, 512, 1024, 2048, and 4096. See Table 3 and Table 4 in the fair-queue (class-default) command for the default number of dynamic queues.
reservable-queues
(Optional) Number of reservable queues used for reserved conversations in the range 0 to 1000. The default is 0. Reservable queues are used for interfaces configured for features such as Resource Reservation Protocol (RSVP).
Defaults
Fair queueing is enabled by default for physical interfaces whose bandwidth is less than or equal to 2.048 Mbps and that do not use the following: X.25 and Synchronous Data Link Control (SDLC) encapsulations; Link Access Procedure, Balanced (LAPB); tunnels; loopbacks; dialer; bridges; or virtual interfaces. Fair queueing is not an option for these protocols. However, if custom queueing or priority queueing is enabled for a qualifying link, it overrides fair queueing, effectively disabling it. Additionally, fair queueing is automatically disabled if you enable the autonomous or silicon switching engine mechanisms.
Note
The number of dynamic queues is derived from the interface or ATM permanent virtual circuit (PVC) bandwidth. See Table 3 in the fair-queue (class-default) command for the default number of dynamic queues that WFQ and class-based WFQ (CBWFQ) use when they are enabled on an interface. See Table 4 in the fair-queue (class-default) command for the default number of dynamic queues used when WFQ and CBWFQ are enabled on an ATM PVC.
Command Modes
Interface configuration
Command History
Usage Guidelines
This command enables WFQ. With WFQ, packets are classified by flow. For example, packets with the same source IP address, destination IP address, source TCP or User Datagram Protocol (UDP) port, destination TCP or UDP port, and protocol belong to the same flow; see Table 6 for a full list of protocols and traffic stream discrimination fields.
When enabled for an interface, WFQ provides traffic priority management that automatically sorts among individual traffic streams without requiring that you first define access lists. Enabling WFQ requires use of this command only.
When WFQ is enabled for an interface, new messages for high-bandwidth traffic streams are discarded after the configured or default congestive discard 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.
WFQ uses a traffic data stream discrimination registry service to determine which traffic stream a message belongs to. For each forwarding protocol, Table 6 shows the attributes of a message that are used to classify traffic into data streams.
It is important to note that IP Precedence, congestion in Frame Relay switching, and discard eligible (DE) flags affect the weights used for queueing.
IP Precedence, which is set by the host or by policy maps, is a number in the range 0 to 7. Data streams of precedence number are weighted so that they are given an effective bit rate of number+1 times as fast as a data stream of precedence 0, which is normal.
In Frame Relay switching, message flags for forward explicit congestion notification (FECN), backward explicit congestion notification (BECN), and DE message flags cause the algorithm to select weights that effectively impose reduced queue priority. The reduced queue priority provides the application with "slow down" feedback and sorts traffic, giving the best service to applications within their committed information rate (CIR).
Fair queueing is supported for all LAN and line (WAN) protocols except X.25, including LAPB and SDLC; see the notes in the section "Defaults." Because tunnels are software interfaces that are themselves routed over physical interfaces, fair queueing is not supported for tunnels. Fair queueing is on by default for interfaces with bandwidth less than or equal to 2 Mbps.
Note
When Resource Reservation Protocol (RSVP) is configured on an interface that supports fair queueing or on an interface that is configured for fair queueing with the reservable queues set to 0 (the default), the reservable queue size is automatically configured using the following method: interface bandwidth divided by 32 kbps. You can override this default by specifying a reservable queue other than 0. For more information on RSVP, refer to the chapter "Configuring RSVP" in the Cisco IOS Quality of Service Solutions Configuration Guide.
Examples
The following example enables use of WFQ on serial interface 0, with a congestive threshold of 300. This threshold means that messages will be discarded from the queueing system only when 300 or more messages have been queued and the message is in a data stream that has more than one message in the queue. The transmit queue limit is set to 2, based on the 384-kilobit (Kb) line set by the bandwidth command:
interface serial 0bandwidth 384fair-queue 300Unspecified parameters take the default values.
The following example requests a fair queue with a congestive discard threshold of 64 messages, 512 dynamic queues, and 18 RSVP queues:
interface Serial 3/0ip unnumbered Ethernet 0/0fair-queue 64 512 18Related Commands
fair-queue aggregate-limit
To set the maximum number of packets in all queues combined for VIP-Distributed weighted fair queueing (DWFQ), use the fair-queue aggregate-limit interface configuration command. To return the value to the default, use the no form of this command.
fair-queue aggregate-limit aggregate-packets
no fair-queue aggregate-limit
Syntax Description
aggregate-packets
Total number of buffered packets allowed before some packets may be dropped. Below this limit, packets will not be dropped.
Defaults
The total number of packets allowed is based on the transmission rate of the interface and the available buffer space on the Versatile Interface Processor (VIP).
Command Modes
Interface configuration
Command History
Usage Guidelines
In general, you should not change the maximum number of packets allows in all queues from the default. Use this command only if you have determined that you would benefit from using a different value, based on your particular situation.
DWFQ keeps track of the number of packets in each queue and the total number of packets in all queues.
When the total number of packets is below the aggregate limit, queues can buffer more packets than the individual queue limit.
When the total number of packets reaches the aggregate limit, the interface starts enforcing the individual queue limits. Any new packets that arrive for a queue that is over its individual queue limit are dropped. Packets that are already in the queue will not be dropped, even if the queue is over the individual limit.
In some cases, the total number of packets in all queues put together may exceed the aggregate limit.
Examples
The following example sets the aggregate limit to 54 packets:
interface Fddi9/0/0fair-queue tosfair-queue aggregate-limit 54Related Commands
fair-queue individual-limit
To set the maximum individual queue depth for VIP-Distributed weighted fair queueing (DWFQ), use the fair-queue individual-limit interface configuration command. To return the value to the default, use the no form of this command.
fair-queue individual-limit individual-packet
no fair-queue individual-limit
Syntax Description
individual-packet
Maximum number of packets allowed in each per-flow or per-class queue during periods of congestion.
Defaults
Half of the aggregate queue limit.
Command Modes
Interface configuration
Command History
Usage Guidelines
In general, you should not change the maximum individual queue depth from the default. Use this command only if you have determined that you would benefit from using a different value, based on your particular situation.
DWFQ keeps track of the number of packets in each queue and the total number of packets in all queues.
When the total number of packets is below the aggregate limit, queues can buffer more packets than the individual queue limit.
When the total number of packets reaches the aggregate limit, the interface starts enforcing the individual queue limits. Any new packets that arrive for a queue that is over its individual queue limit are dropped. Packets that are already in the queue will not be dropped, even if the queue is over the individual limit.
In some cases, the total number of packets in all queues put together may exceed the aggregate limit.
Examples
The following example sets the individual queue limit to 27:
interface Fddi9/0/0mac-address 0000.0c0c.2222ip address 10.1.1.1 255.0.0.0fair-queue tosfair-queue individual-limit 27Related Commands
fair-queue limit
To set the maximum queue depth for a specific VIP-Distributed weighted fair queueing (DWFQ) class, use the fair-queue limit interface configuration command. To return the value to the default, use the no form of this command.
fair-queue {qos-group number | tos number} limit class-packet
no fair-queue {qos-group number | tos number} limit class-packet
Syntax Description
Defaults
The individual queue depth, as specified by the fair-queue individual-limit command. If the fair-queue individual-limit command is not configured, the default is half of the aggregate queue limit.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command to specify the number queue depth for a particular class for class-based DWFQ. This command overrides the global individual limit specified by the fair-queue individual-limit command.
Note
Examples
The following example sets the individual queue limit for ToS group 3 to 20:
interface Fddi9/0/0mac-address 0000.0c0c.2222ip address 10.1.1.1 255.0.0.0fair-queue tosfair-queue tos 3 limit 20Related Commands
fair-queue qos-group
To enable VIP-Distributed weighted fair queueing (DWFQ) and classify packets based on the internal QoS-group number, use the fair-queue qos-group interface configuration command. To disable QoS-group-based DWFQ, use the no form of this command.
fair-queue qos-group
no fair-queue qos-group
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command to enable QoS-group-based DWFQ, a type of class-based DWFQ. Class-based DWFQ overrides flow-based DWFQ. Therefore, this command overrides the fair-queue (DWFQ) command.
When this command is enabled, packets are assigned to different queues based on their QoS group. A QoS group is an internal classification of packets used by the router to determine how packets are treated by certain QoS features, such as DWFQ and committed access rate (CAR). Use a CAR policy or the QoS Policy Propagation via BGP feature to assign packets to QoS groups.
Specify a weight for each class. In periods of congestion, each group is allocated a percentage of the output bandwidth equal to the weight of the class. For example, if a class is assigned a weight of 50, packets from this class are allocated at least 50 percent of the outgoing bandwidth during periods of congestion.
Examples
The following example enables QoS-based DWFQ and allocates bandwidth for nine QoS groups (QoS groups 0 through 8):
interface Hssi0/0/0description 45Mbps to R2ip address 10.200.14.250 255.255.255.252fair-queue qos-groupfair-queue qos-group 1 weight 5fair-queue qos-group 2 weight 5fair-queue qos-group 3 weight 10fair-queue qos-group 4 weight 10fair-queue qos-group 5 weight 10fair-queue qos-group 6 weight 15fair-queue qos-group 7 weight 20fair-queue qos-group 8 weight 29Related Commands
fair-queue tos
To enable VIP-Distributed weighted fair queueing (DWFQ) and classify packets using the type of service (ToS) field of packets, use the fair-queue tos interface configuration command. To disable ToS-based DWFQ, use the no form of this command.
fair-queue tos
no fair-queue tos
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled
By default, class 0 is assigned a weight of 10; class 1 is assigned a weight of 20; class 2 is assigned a weight of 30; and class 3 is assigned a weight of 40.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command to enable ToS-based DWFQ, a type of class-based DWFQ. Class-based DWFQ overrides flow-based DWFQ. Therefore, this command overrides the fair-queue (DWFQ) command.
When this command is enabled, packets are assigned to different queues based on the two low-order IP Precedence bits in the ToS field of the packet header.
In periods of congestion, each group is allocated a percentage of the output bandwidth equal to the weight of the class. For example, if a class is assigned a weight of 50, packets from this class are allocated at least 50 percent of the outgoing bandwidth during periods of congestion.
If you wish to change the weights, use the fair-queue weight command.
Examples
The following example enables ToS-based DWFQ on the High-Speed Serial Interface (HSSI) 0/0/0 interface.
interface Hssi0/0/0description 45Mbps to R2ip address 10.200.14.250 255.255.255.252fair-queuefair-queue tosRelated Commands
fair-queue weight
To assign a weight to a class for VIP-Distributed weighted fair queueing (DWFQ), use the fair-queue weight interface configuration command. To unallocate the bandwidth for the class, use the no form of this command.
fair-queue {qos-group number | tos number} weight weight
no fair-queue {qos-group number | tos number} weight weight
Syntax Description
Defaults
For QoS DWFQ, unallocated bandwidth is assigned to QoS group 0.
For ToS-based DWFQ, class 0 is assigned a weight of 10; class 1 is assigned a weight of 20; class 2 is assigned a weight of 30; and class 3 is assigned a weight of 40.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command to allocate percentages of bandwidth for specific DWFQ classes. You must also enable class-based DWFQ on the interface with either the fair-queue qos-group or fair-queue tos command.
Enter this command once for every class to allocate bandwidth to the class.
For QoS-group-based DWFQ, packets that are not assigned to any QoS groups are assigned to QoS group 0. When assigning weights to QoS group class, remember the following:
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For ToS-based DWFQ, remember the following:
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Examples
The following example allocates bandwidth to different QoS groups. The remaining bandwidth (5 percent) is allocated to QoS group 0.
interface Fddi9/0/0fair-queue qos-groupfair-queue qos-group 1 weight 10fair-queue qos-group 2 weight 15fair-queue qos-group 3 weight 20fair-queue qos-group 4 weight 20fair-queue qos-group 5 weight 30Related Commands
frame-relay ip rtp priority
To reserve a strict priority queue on a Frame Relay permanent virtual circuit (PVC) for a set of Real-Time Transport Protocol (RTP) packet flows belonging to a range of User Datagram Protocol (UDP) destination ports, use the frame-relay ip rtp priority map-class configuration command. To disable the strict priority queue, use the no form of this command.
frame-relay ip rtp priority starting-rtp-port-number port-number-range bandwidth
no frame-relay ip rtp priority
Syntax Description
Defaults
This command has no default behavior or values.
Command Modes
Map-class configuration
Command History
Usage Guidelines
This command is most useful for voice applications, or other applications that are delay-sensitive. To use this command, you must first enter the map-class frame-relay command. After the Frame Relay map class has been configured, it must then be applied to a PVC.
This command extends the functionality offered by the ip rtp priority command by supporting Frame Relay PVCs. The command allows you to specify a range of UDP ports whose voice traffic is guaranteed strict priority service over any other queues or classes using the same output interface. Strict priority means that if packets exist in the priority queue, they are dequeued and sent first—that is, before packets in other queues are dequeued.
Frame Relay traffic shaping (FRTS) and Frame Relay Fragmentation (FRF.12) must be configured before the frame-relay ip rtp priority command is used.
Compressed RTP (CRTP) can be used to reduce the bandwidth required per voice call. When using CRTP with Frame Relay, you must use the encapsulation frame-relay cisco command instead of the encapsulation frame-relay ietf command.
Remember the following guidelines when configuring the bandwidth parameter:
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For more information on IP RTP Priority bandwidth allocation, refer to the section "IP RTP Priority" in the chapter "Congestion Management Overview" in the Cisco IOS Quality of Service Solutions Configuration Guide.
Examples
The following example first configures the Frame Relay map class called voip and then applies the map class to PVC 100 to provide strict priority service to matching RTP packets:
map-class frame-relay voipframe-relay cir 256000frame-relay bc 2560frame-relay be 600frame-relay mincir 256000no frame-relay adaptive-shapingframe-relay fair-queueframe-relay fragment 250frame-relay ip rtp priority 16384 16380 210interface Serial5/0ip address 10.10.10.10 255.0.0.0no ip directed-broadcastencapsulation frame-relayno ip mroute-cacheload-interval 30clockrate 1007616frame-relay traffic-shapingframe-relay interface-dlci 100class voipframe-relay ip rtp header-compressionframe-relay intf-type dceIn this example, RTP packets on PVC 100 with UDP ports in the range of 16384 to 32764 (32764 = 16384 + 16380) will be matched and given strict priority service.
Related Commands
