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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.
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}
Syntax Description
acl-index Access list number. Use any number from 1 to 99 to classify packets by precedence or precedence mask, and use any number from 100 to 199 to classify by MAC address. precedence IP Precedence. mac-address Address of the MAC. mask prec-mask IP Precedence mask; a two-digit hexadecimal number. Use this option when you want to assign multiple precedences to the same rate-limit access list.
Defaults
No CAR access lists are configured.
Command Modes
Global configuration
Command History
11.1 CC This command was introduced.
Release
Modification
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 2 Convert the precedences into an 8-bit number with each bit corresponding to one precedence. For example, an IP Precedence of 0 corresponds to 00000001, 1 corresponds to 00000010, 6 corresponds to 01000000, and 7 corresponds to 10000000.
Step 3 Add the 8-bit numbers for the selected precedences. For example, the mask for precedences 1 and 6 is 01000010.
Step 4 The command expects hexadecimal format. Convert the binary mask into the corresponding hexadecimal number. For example, 01000010 becomes 42. This value is used in the access-list rate-limit command. Any packets that have an IP Precedence of 1 or 6 will match this access list.
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 00e0.34b0.7777
The 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 42
Related 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.
Command
Description
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
12.0(5)T This command was introduced. 12.1(1) The percent keyword was added.
Release
Modification
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).
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Note It is important to remember that hard bandwidth guarantees may not be provided and only relative bandwidths are assured. That is, class bandwidths are always proportional to the specified percentages of the interface bandwidth. When the link bandwidth is fixed, class bandwidth guarantees are in proportion to the configured percentages. If the link bandwidth is unknown or variable, class bandwidth guarantees cannot be computed. |
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:
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 polmap6 class acl22 bandwidth 2000 queue-limit 30
CBWFQ 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 policy1 class class1 bandwidth percent 50 exit class class2 bandwidth percent 25 exit end !The following commands attach the policy to interface s3/2: interface s3/2 service output policy1 end
The 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 s3/2
Serial3/2 output :policy1
Class class1
Weighted Fair Queueing
Output Queue:Conversation 265
Bandwidth 50 (%) Packets Matched 0 Max Threshold 64 (packets)
(discards/tail drops) 0/0
Class class2
Weighted Fair Queueing
Output Queue:Conversation 266
Bandwidth 25 (%) Packets Matched 0 Max Threshold 64 (packets)
(discards/tail drops) 0/0
In 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 policy1 class class1 bandwidth percent 50 exit class class2 bandwidth percent 25 exit end class voice1 priority 500 exit end !The following commands attach the policy to interface s3/2: interface s3/2 service output policy1 end
The 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 policy1
Policy Map policy1
Class class1
Weighted Fair Queueing
Bandwidth 50 (%) Max Threshold 64 (packets)
Class class2
Weighted Fair Queueing
Bandwidth 25 (%) Max Threshold 64 (packets)
Class voice1
Weighted Fair Queueing
Strict Priority
Bandwidth 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
Specifies the name of the class whose policy you want to create or change, and the default class (commonly known as the class-default class) before you configure its policy. max-reserved-bandwidth Changes the percent of interface bandwidth allocated for CBWFQ, LLQ, and IP RTP Priority. policy-map Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy. 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.
Command
Description
Syntax Description
ip-prec-map QoS policy based on the IP Precedence.
Defaults
The Policy Propagation via BGP feature is disabled.
Command Modes
Interface configuration
Command History
11.1 CC This command was introduced.
Release
Modification
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).
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Note If you specify both source and destination keywords on the interface, the software looks up the source address in the routing table and classifies the packet based on the source address first; then the software looks up the destination address in the routing table and reclassifies the packet based on the destination address. |
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 terminal interface ethernet 4/0/0 bgp-policy ip-prec-map end
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}
Syntax Description
implicit Depending on the mode, applies implicit bumping rules, which is also the default, to a single VC bundle member (bundle-vc mode) or all VCs in the bundle (bundle mode). The (default) implicit bumping rule stipulates that bumped traffic is to be carried by a VC with a lower precedence. explicit precedence-level Specifies the precedence level to which traffic on a VC (bundle-vc mode) will be bumped when the VC goes down. Specifies a single number as the value of precedence-level. traffic In its positive form, specifies that the VC accepts bumped traffic. The no form stipulates that the VC does not accept any bumped traffic.
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
12.0(3)T This command was introduced.
Release
Modification
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 When no alternative VC can be found to handle bumped traffic, the bundle is declared down. To avoid this occurrence, configure explicitly the bundle member VC that has the lowest precedence level. |
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):
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-class no bump traffic
bump explicitly 7
Related Commands
class-vc Assigns a VC class to an ATM PVC, SVC, or VC bundle member. precedence Configures precedence levels for a VC class that can be assigned to a VC bundle and thus applied to all VC members of that bundle. protect Configures a VC class with protected group or protected VC status for application to a VC bundle member. ubr Configures UBR QoS and specifies the output peak cell rate for an ATM PVC, SVC, VC class, or VC bundle member. ubr+ Configures UBR QoS and specifies the output peak cell rate and output minimum guaranteed cell rate for an ATM PVC, SVC, VC class, or VC bundle member. vbr-nrt Configures the VBR-NRT QoS and specifies output peak cell rate, output sustainable cell rate, and output maximum burst cell size for an ATM PVC, SVC, VC class, or VC bundle member.
Command
Description
Syntax Description
bundle-name Specifies the name of the bundle to be created. Limit is 16 alphanumeric characters.
Defaults
None
Command Modes
Subinterface configuration
Command History
12.0(3)T This command was introduced.
Release
Modification
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):
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-york
Related Commands
Configures a VC bundle with the bundle-level commands contained in the specified VC class. oam-bundle Enables end-to-end F5 OAM loopback cell generation and OAM management for all VC members of a bundle, or for a VC class that can be applied to a VC bundle. pvc-bundle Adds a PVC to a bundle as a member of the bundle and enters bundle-vc configuration mode in order to configure that PVC bundle member.
Command
Description
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}
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
12.0(5)T This command was introduced.
Release
Modification
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 class1 match access-group 136 class-map class2 match 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 policy1 class class1 bandwidth 2000 queue-limit 40 class class2 bandwidth 3000 random-detect random-detect exponential-weighting-constant 10 class class-default fair-queue 16 queue-limit 20
Class1 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.
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Note Note that when the policy map containing these classes is attached to the interface to stipulate the service policy for that interface, available bandwidth is assessed, taking into account all class policies and Resource Reservation Protocol (RSVP), if configured. |
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 policy2 class class-default fair-queue 20 random-detect random-detect exponential-weighting-constant 14
Related Commands
Specifies or modifies the bandwidth allocated for a class belonging to a policy map. Creates a class map to be used for matching packets to a specified class. policy-map Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy. 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. random-detect exponential-weighting-constant Configures the WRED and DWRED exponential weight factor for the average queue size calculation. random-detect precedence Configures WRED and DWRED parameters for a particular IP Precedence.
Command
Description
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
Syntax Description
vc-class-name Name of the VC class you are assigning to your VC bundle.
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.
Release
Modification
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 class1 encapsulation aal5snap broadcast protocol ip inarp oam-bundle manage 3 oam 4 3 10 ! The following commands apply class1 to the bundle called bundle1: bundle bundle1 class-bundle class1
Taking 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
broadcast Configures broadcast packet duplication and transmission for an ATM VC class, PVC, SVC, or VC bundle. Creates a bundle or modifies an existing bundle to enter bundle configuration mode. class-int Assigns a VC class to an ATM main interface or subinterface. class-vc Assigns a VC class to an ATM PVC, SVC, or VC bundle member. encapsulation Sets the encapsulation method used by the interface. inarp Configures the Inverse ARP time period for an ATM PVC, VC class, or VC bundle. oam-bundle Enables end-to-end F5 OAM loopback cell generation and OAM management for all VC members of a bundle, or for a VC class that can be applied to a VC bundle. oam retry Configures parameters related to OAM management for an ATM PVC, SVC, VC class, or VC bundle. protocol (ATM) Configures a static map for an ATM PVC, SVC, VC class, or VC bundle. Enables Inverse ARP or Inverse ARP broadcasts on an ATM PVC by either configuring Inverse ARP directly on the PVC, on the VC bundle, or in a VC class (applies to IP and IPX protocols only). pvc-bundle Adds a PVC to a bundle as a member of the bundle and enters bundle-vc configuration mode in order to configure that PVC bundle member.
Command
Description
| Command | Description |
show atm bundle | Displays the bundle attributes assigned to each bundle VC member and the current working status of the VC members. |
show atm bundle statistics | Displays statistics on the specified bundle. |
show atm map | Displays the list of all configured ATM static maps to remote hosts on an ATM network. |
vc-class atm | Configures a VC class for an ATM VC or interface. |
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 class-map-name
Syntax Description
class-map-name Name of the class for the class map. The class name is used for both the class map and to configure policy for the class in the policy map.
Defaults
No default behavior.
Command Modes
Global configuration
Command History
12.0(5)T This command was introduced.
Release
Modification
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:
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 class101 match access-group 101
Related Commands
Specifies the name of the class whose policy you want to create or change, and the default class (commonly known as the class-default class) before you configure its policy. match access-group Configures the match criteria for a class map based on the specified ACL number. match input-interface Configures a class map to use the specified input interface as a match criterion. match mpls experimental Configures a class map to use the specified EXP field value as a match criterion. match protocol Configures the match criteria for a class map based on the specified protocol. policy-map Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy.
Command
Description
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
Syntax Description
list Any number from 1 to 16 for the custom queue list.
Defaults
No custom queue list is assigned.
Command Modes
Interface configuration
Command History
10.0 This command was introduced.
Release
Modification
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 0 custom-queue-list 3
Related Commands
queue-list default Assigns a priority queue for those packets that do not match any other rule in the queue list. queue-list interface Establishes queueing priorities on packets entering on an interface. queue-list queue byte-count Specifies how many bytes the system allows to be delivered from a given queue during a particular cycle. queue-list queue limit Designates the queue length limit for a queue. show interfaces Displays statistics for all interfaces configured on the router or access server. show queue Displays the contents of packets inside a queue for a particular interface or VC. show queueing Lists all or selected configured queueing strategies.
Command
Description
Syntax Description
exponent Exponent from 1 to 16 used in the average queue size calculation. The default is 9.
Defaults
The weight factor is 9.
Command Modes
Random-detect-group configuration
Command History
11.1(22)CC This command was introduced.
Release
Modification
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.
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Note The default WRED parameter values are based on the best available data. We recommend that you do not change the parameters from their default values unless you have determined that your applications would benefit from the changed values. |
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 sanjose exponential-weighting-constant 10
Related Commands
protect Configures a VC to belong to the protected group of the bundle or to be an individually protected VC bundle member. random-detect exponential-weighting-constant Configures the WRED and DWRED exponential weight factor for the average queue size calculation. random-detect-group Defines the WRED or DWRED parameter group. show queueing Lists all or selected configured queueing strategies. show queueing interface Displays the queueing statistics of an interface or VC.
Command
Description
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]
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.
| Bandwidth Range | Number of Dynamic Queues |
|---|---|
Less than or equal to 64 kbps | 16 |
More than 64 kbps and less than or equal to 128 kbps | 32 |
More than 128 kbps and less than or equal to 256 kbps | 64 |
More than 256 kbps and less than or equal to 512 kbps | 128 |
More than 512 kbps | 256 |
| Bandwidth Range | Number of Dynamic Queues |
|---|---|
Less than or equal to 128 kbps | 16 |
More than 128 kbps and less than or equal to 512 kbps | 32 |
More than 512 kbps and less than or equal to 2000 kbps | 64 |
More than 2000 kbps and less than or equal to 8000 kbps | 128 |
More than 8000 kbps | 256 |
Command Modes
Policy-map class configuration
Command History
12.0(5)T This command was introduced.
Release
Modification
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 policy9 class class-default fair-queue 16 queue-limit 20
The 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 policy8 class class-default fair-queue 20 random-detect
Related 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.
Command
Description
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-queueSyntax 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.
Table 5 lists the default queue lengths and thresholds.
| Queue or Threshold | Default |
|---|---|
Congestive discard threshold | 64 messages |
Dynamic queues | 256 queues |
Reservable queues | 0 queues |
Command Modes
Interface configuration
Command History
11.1 This command was introduced.
Release
Modification
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 Hssi0/0/0 description 45Mbps to R2 ip address 10.200.14.250 255.255.255.252 fair-queue
Related Commands
Enables WFQ for an interface. Sets the maximum number of packets in all queues combined for DWFQ. Sets the maximum individual queue depth for DWFQ. Sets the maximum queue depth for a specific DWFQ class. Enables DWFQ and classifies packets based on the internal QoS-group number. Enables DWFQ and classifies packets using the ToS field of packets. show interfaces Displays statistics for all interfaces configured on the router or access server. show interfaces fair-queue Displays information and statistics about WFQ for a VIP-based interface.
Command
Description
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]]]
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.
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
11.0 This command was introduced.
Release
Modification
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.
| Forwarder | Fields Used |
|---|---|
AppleTalk |
|
Connectionless Network Service (CLNS) |
|
DECnet |
|
Frame Relay switching |
|
IP |
|
Transparent bridging |
|
Source-route bridging |
|
VINES |
|
Apollo |
|
Xerox Network Systems (XNS) |
|
Novell NetWare |
|
All others (default) |
|
It is important to note that IP Precedence, congestion in Frame Relay switching, and discard eligible (DE) flags affect the weights used for queueing.
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 For Release 10.3 and earlier for the Cisco 7000 and 7500 routers with a Route Switch Processor (RSP) card, if you used the tx-queue-limit command to set the transmit limit available to an interface on a Multiport Communications Interface (MCI) or serial port communications interface (SCI) card and you configured custom queueing or priority queueing for that interface, the configured transmit limit was automatically overridden and set to 1. With Cisco IOS Release 12.0 and later releases, for WFQ, custom queueing, and priority queueing, the configured transmit limit is derived from the bandwidth value set for the interface using the bandwidth command. Bandwidth value divided by 512 rounded up yields the effective transmit limit. However, the derived value only applies in the absence of a tx-queue-limit command; that is, a configured transmit limit overrides this derivation. |
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 0 bandwidth 384 fair-queue 300
Unspecified 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 3/0 ip unnumbered Ethernet 0/0 fair-queue 64 512 18
Related Commands
Assigns a custom queue list to an interface. Specifies the number of dynamic queues to be reserved for use by the class-default class as part of the default class policy. Enables DWFQ. priority-group Assigns the specified priority list to an interface. priority-list default Assigns a priority queue for those packets that do not match any other rule in the priority list. show interfaces Displays statistics for all interfaces configured on the router or access server. show queue Displays the contents of packets inside a queue for a particular interface or VC. show queueing Lists all or selected configured queueing strategies.
Command
Description
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
11.1 CC This command was introduced.
Release
Modification
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 Fddi9/0/0 fair-queue tos fair-queue aggregate-limit 54
Related Commands
Enables DWFQ. Sets the maximum individual queue depth for DWFQ. Sets the maximum queue depth for a specific DWFQ class. Enables DWFQ and classifies packets based on the internal QoS-group number. Enables DWFQ and classifies packets using the ToS field of packets. show interfaces Displays statistics for all interfaces configured on the router or access server. show interfaces fair-queue Displays information and statistics about DWFQ for a VIP-based interface.
Command
Description
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
11.1 CC This command was introduced.
Release
Modification
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 Fddi9/0/0 mac-address 0000.0c0c.2222 ip address 10.1.1.1 255.0.0.0 fair-queue tos fair-queue individual-limit 27
Related Commands
Enables DWFQ for an interface. Sets the maximum number of packets in all queues combined for DWFQ. Sets the maximum queue depth for a specific DWFQ class. Enables DWFQ and classifies packets based on the internal QoS-group number. Enables DWFQ and classifies packets using the ToS field of packets. show interfaces Displays statistics for all interfaces configured on the router or access server. show interfaces fair-queue Displays information and statistics about DWFQ for a VIP-based interface.
Command
Description
Syntax Description
qos-group number Number of the QoS group, as assigned by a committed access rate (CAR) policy or Border Gateway Protocol (BGP) policy propagation. The value can range from 1 to 99. tos number Two low-order IP Precedence bits of the type of service (ToS) field. class-packet Maximum number of packets allowed in the queue for the class during periods of congestion.
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
11.1 CC This command was introduced.
Release
Modification
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 In general, you should not change this value 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. |
Examples
The following example sets the individual queue limit for ToS group 3 to 20:
interface Fddi9/0/0 mac-address 0000.0c0c.2222 ip address 10.1.1.1 255.0.0.0 fair-queue tos fair-queue tos 3 limit 20
Related Commands
Sets the maximum number of packets in all queues combined for DWFQ. Sets the maximum individual queue depth for DWFQ. Enables DWFQ and classifies packets based on the internal QoS-group number. Enables DWFQ and classifies packets using the ToS field of packets. show interfaces Displays statistics for all interfaces configured on the router or access server. show interfaces fair-queue Displays information and statistics about DWFQ for a VIP-based interface.
Command
Description
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Interface configuration
Command History
11.1 CC This command was introduced.
Release
Modification
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 Hssi0/0/0 description 45Mbps to R2 ip address 10.200.14.250 255.255.255.252 fair-queue qos-group fair-queue qos-group 1 weight 5 fair-queue qos-group 2 weight 5 fair-queue qos-group 3 weight 10 fair-queue qos-group 4 weight 10 fair-queue qos-group 5 weight 10 fair-queue qos-group 6 weight 15 fair-queue qos-group 7 weight 20 fair-queue qos-group 8 weight 29
Related Commands
Enables DWFQ for an interface. Sets the maximum number of packets in all queues combined for DWFQ. Sets the maximum individual queue depth for DWFQ. Sets the maximum queue depth for a specific DWFQ class. Enables DWFQ and classifies packets using the ToS field of packets. Assigns a weight to a class for DWFQ. show interfaces Displays statistics for all interfaces configured on the router or access server. show interfaces fair-queue Displays information and statistics about DWFQ for a VIP-based interface.
Command
Description
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
11.1 CC This command was introduced.
Release
Modification
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 Hssi0/0/0 description 45Mbps to R2 ip address 10.200.14.250 255.255.255.252 fair-queue fair-queue tos
Related Commands
Enables DWFQ for an interface. Sets the maximum number of packets in all queues combined for DWFQ. Sets the maximum individual queue depth for DWFQ. Sets the maximum queue depth for a specific DWFQ class. Enables DWFQ and classifies packets based on the internal QoS-group number. Assigns a weight to a class for DWFQ. show interfaces Displays statistics for all interfaces configured on the router or access server. show interfaces fair-queue Displays information and statistics about DWFQ for a VIP-based interface.
Command
Description
Syntax Description
qos-group number Number of the QoS group, as assigned by a committed access rate (CAR) policy or Border Gateway Protocol (BGP) policy propagation. The value range is 1 to 99. tos number Two low-order IP Precedence bits of the type of service (ToS) field. The value range is 1 to 3. weight Percentage of the output link bandwidth allocated to this class. The sum of weights for all classes cannot exceed 99.
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
11.1 CC This command was introduced.
Release
Modification
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:
For ToS-based DWFQ, remember the following:
Examples
The following example allocates bandwidth to different QoS groups. The remaining bandwidth (5 percent) is allocated to QoS group 0.
interface Fddi9/0/0 fair-queue qos-group fair-queue qos-group 1 weight 10 fair-queue qos-group 2 weight 15 fair-queue qos-group 3 weight 20 fair-queue qos-group 4 weight 20 fair-queue qos-group 5 weight 30
Related Commands
Enables DWFQ and classifies packets based on the internal QoS-group number. Enables DWFQ and classifies packets using the ToS field of packets. show interfaces Displays statistics for all interfaces configured on the router or access server. show interfaces fair-queue Displays information and statistics about DWFQ for a VIP-based interface.
Command
Description
Syntax Description
starting-rtp-port-number The starting UDP port number. The lowest port number to which the packets are sent. port-number-range The range of UDP destination ports. Number, which added to the starting-rtp-port-number argument, yields the highest UDP port number. bandwidth Maximum allowed bandwidth (in kbps).
Defaults
This command has no default behavior or values.
Command Modes
Map-class configuration
Command History
12.0(7)T This command was introduced.
Release
Modification
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:
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 voip frame-relay cir 256000 frame-relay bc 2560 frame-relay be 600 frame-relay mincir 256000 no frame-relay adaptive-shaping frame-relay fair-queue frame-relay fragment 250 frame-relay ip rtp priority 16384 16380 210 interface Serial5/0 ip address 10.10.10.10 255.0.0.0 no ip directed-broadcast encapsulation frame-relay no ip mroute-cache load-interval 30 clockrate 1007616 frame-relay traffic-shaping frame-relay interface-dlci 100 class voip frame-relay ip rtp header-compression frame-relay intf-type dce
In 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
ip rtp priority Reserves a strict priority queue on a Frame Relay PVC for a set of RTP packet flows belonging to a range of UDP destination ports. map-class frame-relay Specifies a map class to define QoS values for an SVC. priority Gives priority to a class within a policy map. show frame-relay pvc Displays statistics about PVCs for Frame Relay interfaces. show traffic-shape queue Displays information about the elements queued at a particular time at the VC (DLCI) level. show queue Displays the contents of packets inside a queue for a particular interface or VC.
Command
Description
Posted: Tue Aug 22 12:32:36 PDT 2000
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