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Table Of Contents
Prerequisites for QoS Bandwidth Estimation
Restrictions for QoS Bandwidth Estimation
Information About QoS Bandwidth Estimation
Feature Overview of QoS Bandwidth Estimation
Benefits of QoS Bandwidth Estimation
How to Configure QoS Bandwidth Estimation
Generating a Bandwidth Estimate
Attaching the Policy Map to an Interface
Configuration Examples for QoS Bandwidth Estimation
Generating Bandwidth Estimates for QoS Targets: Example
Attaching the Policy Map to an Interface: Example
Verifying the Configuration: Example
QoS Bandwidth Estimation
The QoS Bandwidth Estimation feature uses Corvil Bandwidth technology to allow you as a network manager to determine the bandwidth requirements to achieve user-specified quality of service (QoS) targets for networked applications.
Feature History for QoS Bandwidth Estimation
Finding Support Information for Platforms and Cisco IOS Software Images
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Contents
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Prerequisites for QoS Bandwidth Estimation
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Prerequisites for QoS Bandwidth Estimation
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Restrictions for QoS Bandwidth Estimation
This feature supports policy maps that are attached to interfaces in an output direction only.
Information About QoS Bandwidth Estimation
To use the QoS Bandwidth Estimation feature, you need to understand the following concepts:
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Feature Overview of QoS Bandwidth Estimation
Allocating adequate bandwidth is key to assuring the network performance required for applications. However, allocating too much bandwidth can be costly. The QoS Bandwidth Estimation feature in Cisco IOS software uses Corvil Bandwidth technology to allow you as a network manager to determine the bandwidth requirements to achieve user-specified quality of service (QoS) targets for networked applications.
Corvil Bandwidth can determine the minimum bandwidth required to deliver traffic within customer-specified QoS targets with statistical reliability. From a network management perspective, an application's QoS requirements are characterized with respect to its sensitivity to packet loss and delay. Corvil Bandwidth provides a way to specify limits for delay and packet loss, and get a tight estimate of the minimum bandwidth essential to achieve desired application performance.
Corvil Bandwidth achieves its results by taking very short timescale (8- millisecond) snapshots of traffic and summarizing them in traffic descriptors that place very low overhead on the router because each descriptor has fewer than 300 bytes. These traffic descriptors record the exceptional events (bursts) and are input to the Corvil Bandwidth algorithm to calculate the minimum bandwidth required to deliver the user-specified QoS target for the observed traffic. (The QoS target is specified in terms of sensitivity to traffic delay and packet loss. For example, voice over IP (VoIP) traffic is very sensitive to both, whereas e-mail file transfer is sensitive to neither.)
As a result, turning on Corvil Bandwidth in the router allows you to obtain bandwidth values that can be used directly to configure the existing Cisco IOS QoS mechanisms on the router to achieve the required application performance as efficiently as possible.
For example, in Figure 1, Corvil Bandwidth is enabled on the router so that the serial interface can deliver the WAN traffic within the customer-specified QoS targets with statistical reliability.
Figure 1 Sample Topology Using QoS Bandwidth Estimation
Applying Corvil Bandwidth
The following sections describe how Corvil Bandwidth can be implemented:
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Link Sizing
To use Corvil Bandwidth to establish the overall bandwidth requirement for a link, you start with QoS targets appropriate for the speed of the link and for the applications being carried on the link (Figure 2). The QoS targets are achieved as long as the link capacity is greater than or equal to the computed Corvil Bandwidth value.
Figure 2 Link Sizing
Bandwidth Allocations by Traffic Class
Corvil Bandwidth can be used to size bandwidth allocations for individual traffic classes defined via the MQC (Figure 3). You specify the QoS target for a traffic class, and Corvil Bandwidth reports the minimum amount of bandwidth that must be allocated to meet that target. The Corvil Bandwidth value can be used directly in the corresponding MQC policy. (The bandwidth allocation is not changed automatically.)
Figure 3 Bandwidth Allocations
Benefits of QoS Bandwidth Estimation
Table 1 shows the features and benefits of QoS Bandwidth Estimation using Corvil Bandwidth technology.
How to Configure QoS Bandwidth Estimation
This section contains the following procedures:
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Generating a Bandwidth Estimate
Perform the following task to generate a bandwidth estimate.
SUMMARY STEPS
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DETAILED STEPS
Attaching the Policy Map to an Interface
Perform the following task to attach the policy map to an interface.
Restrictions
This feature supports policy maps attached to an interface in the output direction only.
SUMMARY STEPS
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DETAILED STEPS
Verifying the Configuration
Perform the following task to verify that bandwidth estimates have been generated.
SUMMARY STEPS
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DETAILED STEPS
Configuration Examples for QoS Bandwidth Estimation
This section contains the following configuration examples:
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Generating Bandwidth Estimates for QoS Targets: Example
In the following example, a policy map and a traffic class are configured. Then bandwidth estimates for QoS targets including packet loss rate, delay time and probability, and timeframe in milliseconds are configured.
Router# configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# policy-map my-policyRouter(config-pmap)# class my-class
Router(config-pmap-c)# bandwidth percent 20
Router(config-pmap-c)# estimate bandwidth drop-one-in 100 delay-one-in 100 milliseconds 50
Router(config-pmap-c)# endAttaching the Policy Map to an Interface: Example
The following example shows the policy map named my-policy being attached to the FastEthernet 0/1 interface in the output direction:
Router# configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# interface f0/1Router(config-if)# service-policy output my-policyRouter(config-if)# endVerifying the Configuration: Example
The following example from the show policy-map interface command verifies that the policy map named my-policy is attached to the FastEthernet 0/1 interface in the output direction and bandwidth estimates have been created:
Router# show policy-map interface f0/1FastEthernet0/1Service-policy output: my-policyClass-map: icmp (match-all)199 packets, 22686 bytes30 second offered rate 0 bps, drop rate 0 bpsMatch: access-group 101Bandwidth Estimation:Quality-of-Service targets:drop no more than one packet in 1000 (Packet loss < 0.10%)delay no more than one packet in 100 by 40 (or more) milliseconds(Confidence: 99.0000%)Corvil Bandwidth: 1 kbits/secClass-map: class-default (match-any)112 packets, 14227 bytes30 second offered rate 0 bps, drop rate 0 bpsMatch: anyBandwidth Estimation:Quality-of-Service targets:<none specified, falling back to drop no more than one packet in 500Corvil Bandwidth: 1 kbits/secAdditional References
The following sections provide references related to the QoS Bandwidth Estimation feature.
Related Documents
QoS commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples
Cisco IOS Quality of Service Solutions Command Reference, Release 12.3 T
MQC
Cisco IOS Quality of Service Solutions Configuration Guide, Release 12.3
Standards
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
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MIBs
RFCs
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.
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Technical Assistance
Command Reference
This section documents new and modified commands.
New Commands
Modified 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 < 2%, 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.
show policy-map interface
To display the packet statistics of all classes that are configured for all service policies either on the specified interface or subinterface or on a specific permanent virtual circuit (PVC) on the interface, use the show policy-map interface command in privileged EXEC mode.
show policy-map interface interface-name [vc [vpi/] vci] [dlci dlci] [input | output]
Syntax Description
Defaults
The absence of both the forward slash (/) and a vpi value defaults the vpi value to 0. If this value is omitted, information for all virtual circuits (VCs) on the specified ATM interface or subinterface is displayed.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The show policy-map interface command displays the packet statistics for classes on the specified interface or the specified PVC only if a service policy has been attached to the interface or the PVC.
You can use the interface-name argument to display output for a PVC only for enhanced ATM port adapters (PA-A3) that support per-VC queueing.
The counters displayed after the show policy-map interface command is entered are updated only if congestion is present on the interface.
The show policy-map interface command displays policy information about Frame Relay PVCs only if Frame Relay Traffic Shaping (FRTS) is enabled on the interface.
The show policy-map interface command displays ECN marking information only if ECN is enabled on the interface.
Examples
This section provides sample output from a typical show policy-map interface command. Depending upon the interface in use and the options enabled, the output you see may vary slightly from the ones shown below. See Table 2 for an explanation of the significant fields that commonly appear in the command output.
The following sample output from the show policy-map interface command displays the statistics for the serial 3/1 interface, to which a service policy called "mypolicy" (configured as shown below) is attached.
policy-map mypolicyclass voicepriority 128class goldbandwidth 100class silverbandwidth 80random-detectRouter# show policy-map output interface serial3/1Serial3/1Service-policy output: mypolicyClass-map: voice (match-all)0 packets, 0 bytes5 minute offered rate 0 bps, drop rate 0 bpsMatch: ip precedence 5Weighted Fair QueueingStrict PriorityOutput Queue: Conversation 264Bandwidth 128 (kbps) Burst 3200 (Bytes)(pkts matched/bytes matched) 0/0(total drops/bytes drops) 0/0Class-map: gold (match-all)0 packets, 0 bytes5 minute offered rate 0 bps, drop rate 0 bpsMatch: ip precedence 2Weighted Fair QueueingOutput Queue: Conversation 265Bandwidth 100 (kbps) Max Threshold 64 (packets)(pkts matched/bytes matched) 0/0(depth/total drops/no-buffer drops) 0/0/0Class-map: silver (match-all)0 packets, 0 bytes5 minute offered rate 0 bps, drop rate 0 bpsMatch: ip precedence 1Weighted Fair QueueingOutput Queue: Conversation 266Bandwidth 80 (kbps)(pkts matched/bytes matched) 0/0(depth/total drops/no-buffer drops) 0/0/0exponential weight: 9mean queue depth: 0class Transmitted Random drop Tail drop Minimum Maximum Markpkts/bytes pkts/bytes pkts/bytes thresh thresh prob0 0/0 0/0 0/0 20 40 1/101 0/0 0/0 0/0 22 40 1/102 0/0 0/0 0/0 24 40 1/103 0/0 0/0 0/0 26 40 1/104 0/0 0/0 0/0 28 40 1/105 0/0 0/0 0/0 30 40 1/106 0/0 0/0 0/0 32 40 1/107 0/0 0/0 0/0 34 40 1/10rsvp 0/0 0/0 0/0 36 40 1/10Class-map: class-default (match-any)0 packets, 0 bytes5 minute offered rate 0 bps, drop rate 0 bpsMatch: anyThe following sample output from the show policy-map interface command displays the statistics for the serial 3/2 interface, to which a service policy called p1 (configured as shown below) is attached. Traffic shaping has been enabled on this interface.
policy-map p1class c1shape average 320000Router# show policy-map output interface serial3/2Serial3/2Service-policy output: p1Class-map: c1 (match-all)0 packets, 0 bytes5 minute offered rate 0 bps, drop rate 0 bpsMatch: ip precedence 0Traffic ShapingTarget Byte Sustain Excess Interval Increment AdaptRate Limit bits/int bits/int (ms) (bytes) Active320000 2000 8000 8000 25 1000 -Queue Packets Bytes Packets Bytes ShapingDepth Delayed Delayed Active0 0 0 0 0 noClass-map: class-default (match-any)0 packets, 0 bytes5 minute offered rate 0 bps, drop rate 0 bpsMatch: anyTable 2 describes the significant fields shown in the displays. The fields in the table are grouped according to the relevant QoS feature.
Table 2 show policy-map interface Field Descriptions 1
Service-policy output
Name of the output service policy applied to the specified interface or VC.
Class-map
Class of traffic being displayed. Output is displayed for each configured class in the policy. The choice for implementing class matches (for example, match-all or match-any) can also appear next to the traffic class.
packets and bytes
Number of packets (also shown in bytes) identified as belonging to the class of traffic being displayed.
offered rate
Rate, in kbps, of packets coming in to the class.
Note
drop rate
Rate, in kbps, at which packets are dropped from the class. The drop rate is calculated by subtracting the number of successfully transmitted packets from the offered rate.
Match
Match criteria specified for the class of traffic. Choices include criteria such as IP precedence, IP differentiated services code point (DSCP) value, Multiprotocol Label Switching (MPLS) experimental (EXP) value, access groups, and QoS groups. For more information about the variety of match criteria options available, refer to the chapter "Configuring the Modular Quality of Service Command-Line Interface" in the Cisco IOS Quality of Service Solutions Configuration Guide.
Output Queue
The weighted fair queueing (WFQ) conversation to which this class of traffic is allocated.
Bandwidth
Bandwidth, in either kbps or percentage, configured for this class and the burst size.
pkts matched/bytes matched
Number of packets (also shown in bytes) matching this class that were placed in the queue. This number reflects the total number of matching packets queued at any time. Packets matching this class are queued only when congestion exists. If packets match the class but are never queued because the network was not congested, those packets are not included in this total. However, if process switching is in use, the number of packets is always incremented even if the network is not congested.
depth/total drops/no-buffer drops
Number of packets discarded for this class. No-buffer indicates that no memory buffer exists to service the packet.
exponential weight
Exponent used in the average queue size calculation for a WRED parameter group.
mean queue depth
Average queue depth based on the actual queue depth on the interface and the exponential weighting constant. It is a fluctuating average. The minimum and maximum thresholds are compared against this value to determine drop decisions.
class
IP precedence level.
Transmitted pkts/bytes
Number of packets (also shown in bytes) passed through WRED and not dropped by WRED.
Note
Random drop pkts/bytes
Number of packets (also shown in bytes) randomly dropped when the mean queue depth is between the minimum threshold value and the maximum threshold value for the specified IP precedence level.
Tail drop pkts/bytes
Number of packets dropped when the mean queue depth is greater than the maximum threshold value for the specified IP precedence level.
Minimum thresh
Minimum threshold. Minimum WRED threshold in number of packets.
Maximum thresh
Maximum threshold. Maximum WRED threshold in number of packets.
Mark prob
Mark probability. Fraction of packets dropped when the average queue depth is at the maximum threshold.
Target Rate
Rate used for shaping traffic.
Byte Limit
Maximum number of bytes that can be transmitted per interval. Calculated as follows:
((Bc+Be) /8) x 1
Sustain bits/int
Committed burst (Bc) rate.
Excess bits/int
Excess burst (Be) rate.
Interval (ms)
Time interval value in milliseconds (ms).
Increment (bytes)
Number of credits (in bytes) received in the token bucket of the traffic shaper during each time interval.
Queue Depth
Current queue depth of the traffic shaper.
Packets
Total number of packets that have entered the traffic shaper system.
Bytes
Total number of bytes that have entered the traffic shaper system.
Packets Delayed
Total number of packets delayed in the queue of the traffic shaper before being transmitted.
Bytes Delayed
Total number of bytes delayed in the queue of the traffic shaper before being transmitted.
Shaping Active
Indicates whether the traffic shaper is active. For example, if a traffic shaper is active, and the traffic being sent exceeds the traffic shaping rate, a "yes" appears in this field.
1 A number in parentheses may appear next to the service-policy output name, class-map name, and match criteria information. The number is for Cisco internal use only and can be disregarded.
Frame Relay Voice-Adaptive Traffic-Shaping show policy interface Command Example
The following sample output shows that Frame Relay voice-adaptive traffic shaping is currently active and has 29 seconds left on the deactivation timer. With traffic shaping active and the deactivation time set, this means that the current sending rate on DLCI 201 is minCIR, but if no voice packets are detected for 29 seconds, the sending rate will increase to CIR.
Router# show policy interface Serial3/1.1Serial3/1.1:DLCI 201 -Service-policy output:MQC-SHAPE-LLQ1Class-map:class-default (match-any)1434 packets, 148751 bytes30 second offered rate 14000 bps, drop rate 0 bpsMatch:anyTraffic ShapingTarget/Average Byte Sustain Excess Interval IncrementRate Limit bits/int bits/int (ms) (bytes)63000/63000 1890 7560 7560 120 945Adapt Queue Packets Bytes Packets Bytes ShapingActive Depth Delayed Delayed ActiveBECN 0 1434 162991 26 2704 yesVoice Adaptive Shaping active, time left 29 secsTable 3 describes the significant fields shown in the display. Significant fields that are not described in Table 3 are described in Table 2, "show policy-map interface Field Descriptions."
Two-Rate Traffic Policing show policy-map interface Command Example
The following is sample output from the show policy-map interface command when two-rate traffic policing has been configured. In the example below, 1.25 Mbps of traffic is sent ("offered") to a policer class.
Router# show policy-map interface serial3/0Serial3/0Service-policy output: policy1Class-map: police (match all)148803 packets, 36605538 bytes30 second offered rate 1249000 bps, drop rate 249000 bpsMatch: access-group 101police:cir 500000 bps, conform-burst 10000, pir 1000000, peak-burst 100000conformed 59538 packets, 14646348 bytes; action: transmitexceeded 59538 packets, 14646348 bytes; action: set-prec-transmit 2violated 29731 packets, 7313826 bytes; action: dropconformed 499000 bps, exceed 500000 bps violate 249000 bpsClass-map: class-default (match-any)19 packets, 1990 bytes30 seconds offered rate 0 bps, drop rate 0 bpsMatch: anyThe two-rate traffic policer marks 500 kbps of traffic as conforming, 500 kbps of traffic as exceeding, and 250 kbps of traffic as violating the specified rate. Packets marked as conforming will be sent as is, and packets marked as exceeding will be marked with IP Precedence 2 and then sent. Packets marked as violating the specified rate are dropped.
Table 4 describes the significant fields shown in the display.
Multiple Traffic Policing Actions show policy-map interface Command Example
The following is sample output from the show policy-map command when the Policer Enhancement — Multiple Actions feature has been configured. The sample output from the show policy-map interface command displays the statistics for the serial 3/2 interface, to which a service policy called "police" (configured as shown below) is attached.
policy-map policeclass class-defaultpolice cir 1000000 pir 2000000conform-action transmitexceed-action set-prec-transmit 4exceed-action set-frde-transmitviolate-action set-prec-transmit 2violate-action set-frde-transmitRouter# show policy-map interface serial3/2Serial3/2: DLCI 100 -Service-policy output: policeClass-map: class-default (match-any)172984 packets, 42553700 bytes5 minute offered rate 960000 bps, drop rate 277000 bpsMatch: anypolice:cir 1000000 bps, bc 31250 bytes, pir 2000000 bps, be 31250 bytesconformed 59679 packets, 14680670 bytes; actions:transmitexceeded 59549 packets, 14649054 bytes; actions:set-prec-transmit 4set-frde-transmitviolated 53758 packets, 13224468 bytes; actions:set-prec-transmit 2set-frde-transmitconformed 340000 bps, exceed 341000 bps, violate 314000 bpsThe sample output from show policy-map interface command shows the following:
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Table 5 describes the significant fields shown in the display.
Explicit Congestion Notification show policy-map interface Command Example
The following is sample output from the show policy-map interface command when the WRED — Explicit Congestion Notification (ECN) feature has been configured. The words "explicit congestion notification" included in the output indicate that ECN has been enabled.
Router# show policy-map interface Serial4/1Serial4/1Service-policy output:policy_ecnClass-map:prec1 (match-all)1000 packets, 125000 bytes30 second offered rate 14000 bps, drop rate 5000 bpsMatch:ip precedence 1Weighted Fair QueueingOutput Queue:Conversation 42Bandwidth 20 (%)Bandwidth 100 (kbps)(pkts matched/bytes matched) 989/123625(depth/total drops/no-buffer drops) 0/455/0exponential weight:9explicit congestion notificationmean queue depth:0class Transmitted Random drop Tail drop Minimum Maximum Markpkts/bytes pkts/bytes pkts/bytes threshold threshold probability0 0/0 0/0 0/0 20 40 1/101 545/68125 0/0 0/0 22 40 1/102 0/0 0/0 0/0 24 40 1/103 0/0 0/0 0/0 26 40 1/104 0/0 0/0 0/0 28 40 1/105 0/0 0/0 0/0 30 40 1/106 0/0 0/0 0/0 32 40 1/107 0/0 0/0 0/0 34 40 1/10rsvp 0/0 0/0 0/0 36 40 1/10class ECN Markpkts/bytes0 0/01 43/53752 0/03 0/04 0/05 0/06 0/07 0/0rsvp 0/0Table 6 describes the significant fields shown in the display.
