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Cisco IOS Quality of Service Solutions Command Reference
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A through C
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D through F
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identity policy (policy-map) through ip rsvp pq-profile
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ip rsvp precedence through load protocol
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match access-group through mls ip pbr
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mls qos (global configuration mode) through mpls experimental
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N through P
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Q through R
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send qdm message through show atm bundle svc statistics
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show auto discovery qos through show ip rsvp hello client lsp detail
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show ip rsvp hello client lsp summary through show lane qos database
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show mls qos through vc-hold-queue
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Table Of Contents
exponential-weighting-constant
frame-relay interface-queue priority
frame-relay ip rtp compression-connections
frame-relay ip rtp header-compression
frame-relay ip tcp compression-connections
frame-relay ip tcp header-compression
frame-relay map ip rtp header-compression
description (class-map)
To add a description to the class map or the policy map, use the description command in class-map configuration or policy-map configuration mode. To remove the description from the class map or the policy map, use the no form of this command.
description character-string
no description
Syntax Description
character-string
Comment or a description that is added to the class map or the policy map. The character-string cannot exceed 161 characters.
Defaults
If this command is not issued, a description does not exist.
Command Modes
Class-map configuration
Policy-map configuration
Command History
Usage Guidelines
The description command is meant solely as a comment to be put in the configuration to help you remember information about the class map or policy map, such as which packets are included within the class map.
Examples
The following example shows how to specify a description within the class map "ip-udp" and the policy map "fpm-policy":
class-map type stack match-all ip-udpdescription "match UDP over IP packets"match field ip protocol eq 0x11 next udp!policy-map type access-control fpm-policydescription "drop worms and malicious attacks"class ip-udpservice-policy fpm-udp-policy!!interface gigabitEthernet 0/1service-policy type access-control input fpm-policyRelated Commands
disconnect qdm
To disconnect a Quality of Service Device Manager (QDM) client, use the disconnect qdm command in EXEC or privileged EXEC mode.
disconnect qdm [client client-id]
Syntax Description
Command Default
This command has no default settings.
Command Modes
EXEC
Privileged EXECCommand History
Usage Guidelines
Use the disconnect qdm command to disconnect all QDM clients that are connected to the router.
Use the disconnect qdm [client client-id] command to disconnect a specific QDM client connected to a router. For instance, using the disconnect qdm client 42 command will disconnect the QDM client with the ID 42.
Note
For the Cisco 7600 series QDM is not supported on Cisco Optical Services Module (OSM) interfaces.
Examples
The following example shows how to disconnect all connected QDM clients:
Router# disconnect qdmThe following example shows how to disconnect a specific QDM client with client ID 9:
Router# disconnect qdm client 9Related Commands
drop
To configure a traffic class to discard packets belonging to a specific class, use the drop command in policy-map class configuration mode. To disable the packet discarding action in a traffic class, use the no form of this command.
drop
no drop
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Policy-map class configuration
Command History
Usage Guidelines
Note the following points when configuring the drop command to unconditionally discard packets in a traffic class:
•
•
•
Examples
In the following example a traffic class called "class1" has been created and configured for use in a policy map called "policy1." The policy map (service policy) is attached to an output serial interface 2/0. All packets matching access-group 101 are placed in a class called "c1." Packets belonging to this class are discarded.
Router(config)# class-map class1Router(config-cmap)# match access-group 101Router(config-cmap)# policy-map policy1Router(config-pmap)# class c1Router(config-pmap-c)# dropRouter(config-pmap-c)# interface s2/0Router(config-if)# service-policy output policy1Router(config-if)# endRelated Commands
dscp
To change the minimum and maximum packet thresholds for the differentiated services code point (DSCP) value, use the dscp command in random-detect-group configuration mode. To return the minimum and maximum packet thresholds to the default for the DSCP value, use the no form of this command.
dscp dscp-value min-threshold max-threshold [mark-probability-denominator]
no dscp dscp-value min-threshold max-threshold [mark-probability-denominator]
Syntax Description
Command Default
If WRED is using the DSCP value to calculate the drop probability of a packet, all entries of the DSCP table are initialized with the default settings shown in Table 7 of the "Usage Guidelines" section.
Command Modes
Random-detect-group configuration
Command History
Usage Guidelines
This command must be used in conjunction with the random-detect-group command.
Additionally, the dscp command is available only if you specified the dscp-based argument when using the random-detect-group command.
Table 7 lists the DSCP default settings used by the dscp command. Table 7 lists the DSCP value, and its corresponding minimum threshold, maximum threshold, and mark probability. The last row of the table (the row labeled "default") shows the default settings used for any DSCP value not specifically shown in the table.
Examples
The following example enables WRED to use the DSCP value af22. The minimum threshold for the DSCP value af22 is 28, the maximum threshold is 40, and the mark probability is 10.
Router> enable
Router# configure terminal
Router(config)# random-detect-group class1 dscp-based
Router(cfg-red-group)# dscp af22 28 40 10
Router(cfg-red-group)# end
Related Commands
estimate bandwidth
To estimate the bandwidth needed per traffic class for given quality of service (QoS) targets based on traffic data, use the estimate bandwidth command in policy-map class configuration mode. To disable the estimated bandwidth processing, use the no form of this command.
estimate bandwidth [drop-one-in n] [delay-one-in n milliseconds n]
no estimate bandwidth
Syntax Description
Defaults
Disabled
Command Modes
Policy-map class configuration
Command History
Usage Guidelines
Use the estimate bandwidth command to specify the target drop probability, the delay time and probability, and the timeframe.
If you specify a delay time, you must also specify a delay threshold.
If you issue the estimate bandwidth command with no keywords, the default target is drop less than 2 percent, which is the same as entering estimate bandwidth drop-one-in 500.
Examples
In the following example, the QoS targets are drop no more than one packet in 100, and delay no more than one packet in 100 by more than 50 milliseconds:
Router(config-pmap-c)# estimate bandwidth drop-one-in 100 delay-one-in 100 milliseconds 50Related Commands
bandwidth (policy-map class)
Specifies or modifies the bandwidth allocated for a class belonging to a policy map.
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 command in random-detect-group configuration mode. 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
Command Default
The default 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 called 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 command in policy-map class configuration mode. 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 that specifies the number of dynamic queues. Range is from 16 to 4096.
Command Default
The number of dynamic queues is derived from the interface or ATM permanent virtual circuit (PVC) bandwidth. See Table 8 in the "Usage Guidelines" section 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 9 in the "Usage Guidelines" section 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.
Table 8 lists the default number of dynamic queues that weighted fair queueing (WFQ) and class-based WFQ (CBWFQ) use when they are enabled on an interface.
Table 9 lists the default number of dynamic queues used when WFQ or CBWFQ is enabled on an ATM PVC.
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 64random-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 Versatile Interface Processor (VIP)-distributed weighted fair queueing (DWFQ), use the fair-queue command in interface configuration mode. To disable DWFQ, use the no form of this command.
fair-queue
no fair-queue
Syntax Description
This command has no arguments or keywords.
Command Default
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 (MLP).
See Table 10 in the "Usage Guidelines" section of this command for a list of the default queue lengths and thresholds.
Command Modes
Interface configuration
Command History
Usage Guidelines
The fair-queue (DWFQ) command enables DWFQ on an interface using a VIP2-40 or greater interface processor.
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.
Table 10 lists the default queue lengths and thresholds.
Table 10 Default Fair Queue Lengths and Thresholds
Congestive discard threshold
64 messages
Dynamic queues
256 queues
Reservable queues
0 queues
Examples
The following example enables DWFQ on the High-Speed Serial Interface (HSSI) interface 0/0/0:
interface Hssi0/0/0description 45Mbps to R2ip address 10.200.14.250 255.255.255.252fair-queueRelated Commands
fair-queue (policy-map class)
To specify the number of queues to be reserved for use by a traffic class, use the fair-queue command in policy-map class configuration mode. To delete the configured number of queues from the traffic class, use the no form of this command.
fair-queue [dynamic-queues]
no fair-queue [dynamic-queues]
Syntax Description
dynamic-queues
(Optional) A number specifying the number of dynamic conversation queues. The number can be in the range of 16 to 4096.
Command Default
No queues are reserved.
Command Modes
Policy-map class configuration
Command History
Usage Guidelines
On a VIP, the fair-queue command can be used for any traffic class (as opposed to non-VIP platforms, which can only use the fair-queue command in the default traffic class). The fair-queue command can be used in conjunction with either the queue-limit command or the random-detect exponential-weighting-constant command.
Examples
The following example configures the default traffic class for the policy map called policy9 to reserve ten queues for packets that do not satisfy match criteria specified for other traffic classes whose policy is configured in the same service policy. Because the queue-limit command is configured, tail drop is used for each queue when the maximum number of packets is enqueued and additional packets arrive.
policy-map policy9 class class-default fair-queue 10queue-limit 20The following example configures a service policy called policy8 that is associated with a user-defined traffic class called class1. The fair-queue command reserves 20 queues to be used for the service policy. For congestion avoidance, Weighted Random Early Detection (WRED) or distributed WRED (DWRED) packet drop is used, not tail drop.
policy-map policy8 class class1 fair-queue 20random-detect exponential-weighting-constant 14Related Commands
fair-queue (WFQ)
To enable weighted fair queueing (WFQ), use the fair-queue command in interface configuration or policy-map class configuration mode. To disable WFQ, use the no form of this command.
fair-queue [congestive-discard-threshold [dynamic-queues [reservable-queues]]]
no fair-queue
Syntax Description
Command Default
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:
•
•
•
•
•
•
•
Fair queueing is not an option for the protocols listed above. 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 11 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 11 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 (config-if)
Policy-map class configuration (config-pmap-c)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 11 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 11 shows the message attributes that are used to classify traffic into data streams.
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 from 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 you configure Resource Reservation Protocol (RSVP) 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.
Beginning with Cisco IOS Release 12.4(20)T, if your image has HQF support, the fair-queue command is not enabled automatically under class default. You should enable the fair-queue command and any other supported queueing features before using an HQF-capable image.
Examples
The following example enables WFQ on serial interface 0, with a congestive threshold of 300. This threshold means that messages are 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 18You can apply the fair-queue command to a user-defined class as shown in the following example:
policy-map p1class c1bandwidth 1000fair-queueRelated Commands
fair-queue aggregate-limit
To set the maximum number of packets in all queues combined for Versatile Interface Processor (VIP)-distributed weighted fair queueing (DWFQ), use the fair-queue aggregate-limit command in interface configuration mode. 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.
Command Default
The total number of packets allowed is based on the transmission rate of the interface and the available buffer space on the 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 Versatile Interface Processor (VIP)-distributed weighted fair queueing (DWFQ), use the fair-queue individual-limit command in interface configuration mode. 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.
Command Default
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 Versatile Interface Processor (VIP)-distributed weighted fair queueing (DWFQ) class, use the fair-queue limit command in interface configuration mode. 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
