Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide - Configuring Modular QoS Congestion Management [Cisco IOS XR Software (End-of-Sale)]

Table Of Contents

Configuring Modular QoS Congestion Management on Cisco ASR 9000 Series Routers

Contents

Prerequisites for Configuring QoS Congestion Management on Cisco ASR 9000 Series Routers

Information About Configuring QoS Congestion Management on Cisco ASR 9000 Series Routers

Congestion Management Overview

Modified Deficit Round Robin

Low-Latency Queueing with Strict Priority Queueing

Traffic Shaping

Traffic-Shaping Mechanism Regulates Traffic

Traffic Policing

Hierarchical Policing

Packet Marking Through the IP Precedence Value, IP DSCP Value, and the MPLS Experimental Value Setting

Regulation of Traffic with the Policing Mechanism

Traffic Shaping Versus Traffic Policing

Congestion Management Using DEI

How to Configure QoS Congestion Management on Cisco ASR 9000 Series Routers

Configuring Guaranteed and Remaining Bandwidths

Restrictions

Configuring Guaranteed Bandwidth

Configuring Bandwidth Remaining

Configuring Low-Latency Queueing with Strict Priority Queueing

Restrictions

Configuring Traffic Shaping

Restrictions

Configuring Traffic Policing

Configuring Hierarchical Policing

Configuration Examples for Configuring QoS Congestion Management on Cisco ASR 9000 Series Routers

Traffic Shaping for an Input Interface: Example

Traffic Policing for a Bundled Interface: Example

Hierarchical Policing: Example

Multi-action Set/Policer: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Configuring Modular QoS Congestion Management on Cisco ASR 9000 Series Routers

Congestion management controls congestion after it has occurred on a network. Congestion can be managed on Cisco IOS XR software by using packet queueing methods, and by shaping the packet flow through use of traffic regulation mechanisms.

Packet queueing methods define packet scheduling or the order in which packets are dequeued to the interface for transmission on the physical wire. Furthermore, queueing methods support minimum bandwidth guarantees and low latencies based on the order and number of times that a queue is serviced.

The following types of queueing methods and traffic regulation mechanisms are supported on the Cisco ASR 9000 Series Aggregation Services Routers :

•Modified Deficit Round Robin (MDRR)

•Low-latency queueing (LLQ) with strict priority queueing (PQ)

•Traffic shaping

•Traffic policing

Line Card, SIP, and SPA Support

Feature

ASR 9000 Ethernet Line Cards

SIP 700 for the ASR 9000

Congestion Management Using DEI

yes

no

Guaranteed and Remaining Bandwidth

yes

yes

Low-Latency Queueing with Strict Priority Queueing

yes

yes

Traffic Policing

yes

yes

Traffic Shaping

yes

yes

Feature History for Configuring Modular QoS Congestion Management on Cisco ASR 9000 Series Routers

Release

Modification

Release 3.7.2

The Congestion Avoidance feature was introduced on ASR 9000 Ethernet Line Cards..

The Guaranteed and Remaining Bandwidth, Low-Latency Queueing with Strict Priority Queueing, Traffic Policing, and Traffic Shaping features were introduced on ASR 9000 Ethernet Line Cards.

Release 3.9.0

The Guaranteed and Remaining Bandwidth, Low-Latency Queueing with Strict Priority Queueing, Traffic Policing, and Traffic Shaping features were supported on the SIP 700 for the ASR 9000.

Release 4.0

The Congestion Management Using DEI feature was introduced on ASR 9000 Ethernet Line Cards.

Release 4.0.1

The police rate command was updated to include packet-based specifications of policing rates and burst sizes.

Contents

•Prerequisites for Configuring QoS Congestion Management on Cisco ASR 9000 Series Routers

•Information About Configuring QoS Congestion Management on Cisco ASR 9000 Series Routers

•How to Configure QoS Congestion Management on Cisco ASR 9000 Series Routers

•Configuration Examples for Configuring QoS Congestion Management on Cisco ASR 9000 Series Routers

•Additional References

Prerequisites for Configuring QoS Congestion Management on Cisco ASR 9000 Series Routers

The following prerequisites are required for configuring QoS congestion management on your network:

•You must be in a user group associated with a task group that includes the proper task IDs. The command reference guides include the task IDs required for each command. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

•You must be familiar with Cisco IOS XR QoS configuration tasks and concepts.

Information About Configuring QoS Congestion Management on Cisco ASR 9000 Series Routers

To implement QoS congestion management features in this document, you must understand the following concepts:

•Congestion Management Overview

•Modified Deficit Round Robin

•Low-Latency Queueing with Strict Priority Queueing

•Traffic Shaping

•Traffic-Shaping Mechanism Regulates Traffic

•Traffic Policing

•Regulation of Traffic with the Policing Mechanism

•Traffic Shaping Versus Traffic Policing

Congestion Management Overview

Congestion management features allow you to control congestion by determining the order in which a traffic flow (or packets) is sent out an interface based on priorities assigned to packets. Congestion management entails the creation of queues, assignment of packets to those queues based on the classification of the packet, and scheduling of the packets in a queue for transmission. The congestion management features in Cisco IOS XR software allow you to specify creation of a different number of queues, affording greater or lesser degree of differentiation of traffic, and to specify the order in which that traffic is sent.

During periods with light traffic flow, that is, when no congestion exists, packets are sent out the interface as soon as they arrive. During periods of transmit congestion at the outgoing interface, packets arrive faster than the interface can send them. If you use congestion management features, packets accumulating at an interface are queued until the interface is free to send them; they are then scheduled for transmission according to their assigned priority and the queueing method configured for the interface. The router determines the order of packet transmission by controlling which packets are placed in which queue and how queues are serviced with respect to each other.

In addition to queueing methods, QoS congestion management mechanisms, such as policers and shapers, are needed to ensure that a packet adheres to a contract and service. Both policing and shaping mechanisms use the traffic descriptor for a packet. See the "Configuring Modular Quality of Service Congestion Management on Cisco ASR 9000 Series Routers" module in this guide for information about the traffic descriptor.

Policers and shapers usually identify traffic descriptor violations in an identical manner through the token bucket mechanism, but they differ in the way they respond to violations. A policer typically drops traffic flow; whereas, a shaper delays excess traffic flow using a buffer, or queueing mechanism, to hold the traffic for transmission at a later time.

Traffic shaping and policing can work in tandem. For example, a good traffic shaping scheme should make it easy for nodes inside the network to detect abnormal flows.

Modified Deficit Round Robin

MDRR is a class-based composite scheduling mechanism that allows for queueing of up to eight traffic classes. It operates in the same manner as class-based weighted fair queueing (CBWFQ) and allows definition of traffic classes based on customer match criteria (such as access lists); however, MDRR does not use the weighted fair queueing algorithm.

When MDRR is configured in the queueing strategy, nonempty queues are served one after the other. Each time a queue is served, a fixed amount of data is dequeued. The algorithm then services the next queue. When a queue is served, MDDR keeps track of the number of bytes of data that were dequeued in excess of the configured value. In the next pass, when the queue is served again, less data is dequeued to compensate for the excess data that was served previously. As a result, the average amount of data dequeued per queue is close to the configured value. In addition, MDRR allows for a strict priority queue for delay-sensitive traffic.

Each queue within MDRR is defined by two variables:

•Quantum value—Average number of bytes served in each round.

•Deficit counter—Number of bytes a queue has sent in each round. The counter is initialized to the quantum value.

Packets in a queue are served as long as the deficit counter is greater than zero. Each packet served decreases the deficit counter by a value equal to its length in bytes. A queue can no longer be served after the deficit counter becomes zero or negative. In each new round, the deficit counter for each nonempty queue is incremented by its quantum value.

Low-Latency Queueing with Strict Priority Queueing

The LLQ feature brings strict priority queueing (PQ) to the MDRR scheduling mechanism. PQ in strict priority mode ensures that one type of traffic is sent, possibly at the expense of all others. For PQ, a low-priority queue can be detrimentally affected, and, in the worst case, never allowed to send its packets if a limited amount of bandwidth is available or the transmission rate of critical traffic is high.

Strict PQ allows delay-sensitive data, such as voice, to be dequeued and sent before packets in other queues are dequeued.

LLQ enables the use of a single, strict priority queue within MDRR at the class level, allowing you to direct traffic belonging to a class. To rank class traffic to the strict priority queue, you specify the named class within a policy map and then configure the priority command for the class. (Classes to which the priority command is applied are considered priority classes.) Within a policy map, you can give one or more classes priority status. When multiple classes within a single policy map are configured as priority classes, all traffic from these classes is enqueued to the same, single, strict priority queue.

Through use of the priority command, you can assign a strict PQ to any of the valid match criteria used to specify traffic. These methods of specifying traffic for a class include matching on access lists, protocols, IP precedence, and IP differentiated service code point (DSCP) values. Moreover, within an access list you can specify that traffic matches are allowed based on the DSCP value that is set using the first six bits of the IP type of service (ToS) byte in the IP header.

Traffic Shaping

Traffic shaping allows you to control the traffic flow exiting an interface to match its transmission to the speed of the remote target interface and ensure that the traffic conforms to policies contracted for it. Traffic adhering to a particular profile can be shaped to meet downstream requirements, thereby eliminating bottlenecks in topologies with data-rate mismatches.

To match the rate of transmission of data from the source to the target interface, you can limit the transfer of data to one of the following:

•A specific configured rate

•A derived rate based on the level of congestion

The rate of transfer depends on these three components that constitute the token bucket: burst size, mean rate, and time (measurement) interval. The mean rate is equal to the burst size divided by the interval.

When traffic shaping is enabled, the bit rate of the interface does not exceed the mean rate over any integral multiple of the interval. In other words, during every interval, a maximum of burst size can be sent. Within the interval, however, the bit rate may be faster than the mean rate at any given time.

When the peak burst size equals 0, the interface sends no more than the burst size every interval, achieving an average rate no higher than the mean rate. However, when the peak burst size is greater than 0, the interface can send as many as the burst size plus peak burst bits in a burst, if in a previous time period the maximum amount was not sent. Whenever less than the burst size is sent during an interval, the remaining number of bits, up to the peak burst size, can be used to send more than the burst size in a later interval.

Traffic-Shaping Mechanism Regulates Traffic

When incoming packets arrive at an interface, the packets are classified using a classification technique, such as an access control list (ACL) or the setting of the IP Precedence bits through the Modular QoS CLI (MQC). If the packet matches the specified classification, the traffic-shaping mechanism continues. Otherwise, no further action is taken.

Figure 1 illustrates how a traffic shaping mechanism regulates traffic flow.

Figure 1 How a Traffic Shaping Mechanism Regulates Traffic

Packets matching the specified criteria are placed in the token bucket. The maximum size of the token bucket is the confirm burst (Bc) size plus the Be size. The token bucket is filled at a constant rate of Bc worth of tokens at every Tc. This is the configured traffic shaping rate.

If the traffic shaping mechanism is active (that is, packets exceeding the configured traffic shaping rate already exist in a transmission queue) at every Tc, the traffic shaper checks to see if the transmission queue contains enough packets to send (that is, up to either Bc [or Bc plus Be] worth of traffic).

If the traffic shaper is not active (that is, there are no packets exceeding the configured traffic shaping rate in the transmission queue), the traffic shaper checks the number of tokens in the token bucket. One of the following occurs:

•If there are enough tokens in the token bucket, the packet is sent (transmitted).

•If there are not enough tokens in the token bucket, the packet is placed in a shaping queue for transmission at a later time.

Traffic Policing

In general, traffic policing allows you to control the maximum rate of traffic sent or received on an interface, and to partition a network into multiple priority levels or class of service (CoS).

Traffic policing manages the maximum rate of traffic through a token bucket algorithm. The token bucket algorithm can use the user-configured values to determine the maximum rate of traffic allowed on an interface at a given moment in time. The token bucket algorithm is affected by all traffic entering or leaving (depending on where the traffic policy with traffic policing is configured) and is useful in managing network bandwidth in cases in which several large packets are sent in the same traffic stream.

Traffic policing is often configured on interfaces at the edge of a network to limit the rate of traffic entering or leaving the network. In the most common traffic policing configurations, traffic that conforms is sent and traffic that exceeds is sent with a decreased priority or is dropped. Users can change these configuration options to suit their network needs. Traffic policing also provides a certain amount of bandwidth management by allowing you to set the burst size (Bc) for the committed information rate (CIR). When the peak information rate (PIR) is supported, a second token bucket is enforced and the traffic policer is then called a two-rate policer.

Note The two-rate policer and two-token bucket algorithm is supported in Cisco IOS XR software.

For Cisco IOS XR software, a single-rate, two-color policer is supported that provides one token bucket with two actions for each packet: a conform action and an exceed action.

Hierarchical Policing

The Hierarchical Policing feature is an MQC-based solution that supports hierarchical policing on both the ingress and egress interfaces on Cisco ASR 9000 Series Routers.

This feature allows enforcement of service level agreements (SLA) while applying the classification submodel for different QoS classes on the inbound interface.

Hiearchical policing provides support at two levels:

•Parent level

•Child level

•

Packet Marking Through the IP Precedence Value, IP DSCP Value, and the MPLS Experimental Value Setting

In addition to rate-limiting, traffic policing allows you to independently mark (or classify) the packet according to whether the packet conforms or violates a specified rate. Packet marking also allows you to partition your network into multiple priority levels or CoS. Packet marking as a policer action is conditional marking.

Use the traffic policer to set the IP precedence value, IP DSCP value, or Multiprotocol Label Switching (MPLS) experimental value for packets that enter the network. Then networking devices within your network can use this setting to determine how the traffic should be treated. For example, the Weighted Random Early Detection (WRED) feature uses the IP precedence value to determine the probability that a packet is dropped.

If you want to mark traffic but do not want to use traffic policing, see the "Class-based, Unconditional Packet Marking Examples" section in this guide to learn how to perform packet classification.

Note Marking IP fields on an MPLS-enabled interface results in non-operation on that particular interface.

Regulation of Traffic with the Policing Mechanism

Figure 2 illustrates how a single-rate token bucket policer marks packets as either conforming or exceeding a CIR.

Figure 2 How a Traffic Policing Mechanism Regulates Traffic

The time interval between token updates (Tc) to the token bucket is updated at the CIR value each time a packet arrives at the traffic policer. The Tc token bucket can contain up to the Bc value. If a packet of size B is greater than the Tc token bucket, then the packet exceeds the CIR value and a configured action is performed. If a packet of size B is less than the Tc token bucket, then the packet conforms and a different configured action is performed.

Traffic Shaping Versus Traffic Policing

Although traffic shaping and traffic policing can be implemented together on the same network, there are distinct differences between them, as shown in Table 1.

Table 1 Differences Between Traffic Shaping and Traffic Policing

Traffic Shaping

Traffic Policing

Triggering Event

•Occurs automatically at regular intervals (Tc).

or

Occurs whenever a packet arrives at an interface.

•Occurs whenever a packet arrives at an interface.

What it Does

•Classifies packets.

•If a packet does not meet match criteria, no further action is taken.

•Packets meeting match criteria are sent (if there are enough tokens in the token bucket)

or

Packets are placed in a queue for transmission later.

•If the number of packets in the queue exceed the queue limit, the packets are dropped.

•Classifies packets.

•If a packet does not meet match criteria, no further action is taken.

•Packets meeting match criteria and conforming to or exceeding a specified rate, receive the configured policing action (for example, drop, send, mark, then send).

•Packets are not placed in a queue for transmission later.

Congestion Management Using DEI

You can manage congestion based on the Drop Eligible Indicator (DEI) bit that is present in 802.1ad frames and 802.1ah frames. Random early detection based on the DEI value is supported on 802.1ad packets for:

•Layer 2 subinterfaces

•Layer 2 main interfaces

•Layer 3 main interfaces

•Ingress and egress

Note If there are any marking actions in the policy, the marked values are used for doing WRED.

How to Configure QoS Congestion Management on Cisco ASR 9000 Series Routers

This section contains instructions for the following tasks:

•Configuring Guaranteed and Remaining Bandwidths

•Configuring Low-Latency Queueing with Strict Priority Queueing

•Configuring Traffic Shaping

•Configuring Traffic Policing

Configuring Guaranteed and Remaining Bandwidths

Guaranteed Service rate of a queue is defined as the bandwidth the queue receives when all the queues are congested. It is defined as:

Guaranteed Service Rate = minimum bandwidth + excess share of the queue

The bandwidth command allows you to specify the minimum guaranteed bandwidth to be allocated for a specific class of traffic. MDRR is implemented as the scheduling algorithm.

The bandwidth remaining command specifies a weight for the class to the MDRR. The MDRR algorithm derives the weight for each class from the bandwidth remaining value allocated to the class. The bandwidth remaining is divided among the classes in a policy using either bandwidth remaining ratio or bandwidth remaining percent commands. If you do not configure the bandwidth remaining command for any class, the leftover bandwidth is allocated equally to all classes for which bandwidth remaining is not explicitly specified.

Restrictions

The amount of bandwidth configured should be large enough to also accommodate Layer 2 overhead.

The bandwidth command is supported only on policies configured on outgoing interfaces.

Configuring Guaranteed Bandwidth

SUMMARY STEPS

1. configure

2. policy-map policy-name

3. class class-name

4. bandwidth {rate [units] | percent percentage-value}

5. exit

6. class class-name

7. bandwidth {rate [units] | percent percentage-value}

8. exit

9. class class-name

10. bandwidth {rate [units] | percent percentage-value}

11. exit

12. exit

13. interface type interface-path-id

14. service-policy {input | output} policy-map

15. end
or
commit

16. show policy-map interface type interface-path-id [input | output]

DETAILED STEPS
Command or Action

Purpose

Step 1

configure
Example:

RP/0/RSP0/CPU0:router# configure

Enters global configuration mode.

Step 2

policy-map policy-name
Example:

RP/0/RSP0/CPU0:router(config)# policy-map policy1

Enters policy map configuration mode.

•Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy.

Step 3

class class-name
Example:

RP/0/RSP0/CPU0:router(config-pmap)# class class1

Specifies the name of the class whose policy you want to create or change.

Step 4

bandwidth {rate [units]| percent percentage-value}
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# bandwidth percent 40

Enters policy map class configuration mode.

•Specifies the bandwidth allocated for a class belonging to a policy map.

•In this example, class class1 is guaranteed 40 percent of the interface bandwidth.

Step 5

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# exit

Returns the router to policy map configuration mode.

Step 6

class class-name
Example:

RP/0/RSP0/CPU0:router(config-pmap)# class class2

Specifies the name of the class whose policy you want to create or change.

Step 7

bandwidth {rate [units]| percent percentage-value}
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# bandwidth percent 40

Enters policy map class configuration mode.

•Specifies the bandwidth allocated for a class belonging to a policy map.

•In this example, class class2 is guaranteed 40 percent of the interface bandwidth.

Step 8

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# exit

Returns the router to policy map configuration mode.

Step 9

class class-name
Example:

RP/0/RSP0/CPU0:router(config-pmap)# class class-default

Specifies the name of the class whose policy you want to create or change.

Step 10

bandwidth {rate [units]| percent percentage-value}
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# bandwidth percent 20

Enters policy map class configuration mode.

•Specifies the bandwidth allocated for a class belonging to a policy map.

•In this example, class class-default is guaranteed 20 percent of the interface bandwidth.

Step 11

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# exit

Returns the router to policy map configuration mode.

Step 12

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap)# exit

Returns the router to global configuration mode.

Step 13

interface type interface-path-id
Example:

RP/0/RSP0/CPU0:router(config)# interface gigabitethernet 0/2/0/0

Enters interface configuration mode and configures an interface.

Step 14

service-policy {input | output} policy-map
Example:

RP/0/RSP0/CPU0:router(config-if)# service-policy output policy1

Attaches a policy map to an input or output interface to be used as the service policy for that interface.

•In this example, the traffic policy evaluates all traffic leaving that interface.
Step 15

end
or

commit
Example:

RP/0/RSP0/CPU0:router(config-if)# end
or

RP/0/RSP0/CPU0:router(config-if)# commit
Saves configuration changes.

•When you issue the end command, the system prompts you to commit changes:
Uncommitted changes found, commit them before 
exiting(yes/no/cancel)? 
[cancel]:
–Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

–Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

–Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

•Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.
Step 16

show policy-map interface type interface-path-id [input | output]
Example:

RP/0/RSP0/CPU0:router# show policy-map interface gigabitethernet 0/2/0/0

(Optional) Displays policy configuration information for all classes configured for all service policies on the specified interface.
Configuring Bandwidth Remaining

SUMMARY STEPS

1. configure

2. policy-map policy-name

3. class class-name

4. bandwidth remaining {percent percentage-value | ratio ratio-value}

5. exit

6. class class-name

7. bandwidth remaining {percent percentage-value | ratio ratio-value}

8. exit

9. class class-name

10. bandwidth remaining {percent percentage-value | ratio ratio-value}

11. exit

12. exit

13. interface type interface-path-id

14. service-policy {input | output} policy-map

15. end
or
commit

16. show policy-map interface type instance [input | output]

DETAILED STEPS
Command or Action

Purpose

Step 1

configure
Example:

RP/0/RSP0/CPU0:router# configure

Enters global configuration mode.

Step 2

policy-map policy-name
Example:

RP/0/RSP0/CPU0:router(config)# policy-map policy1

Enters policy map configuration mode.

•Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy.

Step 3

class class-name
Example:

RP/0/RSP0/CPU0:router(config-pmap)# class class1

Specifies the name of the class whose policy you want to create or change.

Step 4

bandwidth remaining percent percentage-value
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# bandwidth remaining percent 40

Specifies how to allocate leftover bandwidth for class class1.

Step 5

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# exit

Returns the router to policy map configuration mode.

Step 6

class class-name
Example:

RP/0/RSP0/CPU0:router(config-pmap)# class class2

Specifies the name of the class whose policy you want to create or change.

Step 7

bandwidth remaining percent percentage-value
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# bandwidth remaining percent 40

Specifies how to allocate leftover bandwidth for class class2.

Step 8

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# exit

Returns the router to policy map configuration mode.

Step 9

class class-name
Example:

RP/0/RSP0/CPU0:router(config-pmap)# class class-default

Specifies the name of the class whose policy you want to create or change.

Step 10

bandwidth remaining percent percentage-value
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# bandwidth remaining percent 20

Specifies how to allocate leftover bandwidth for class class-default.

Step 11

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# exit

Returns the router to policy map configuration mode.

Step 12

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap)# exit

Returns the router to global configuration mode.

Step 13

interface type interface-path-id
Example:

RP/0/RSP0/CPU0:router(config)# interface gigabitethernet 0/2/0/0

Enters interface configuration mode and configures an interface.

Step 14

service-policy {input | output} policy-map
Example:

RP/0/RSP0/CPU0:router(config-if)# service-policy output policy1

Attaches a policy map to an input or output interface to be used as the service policy for that interface.

•In this example, the traffic policy evaluates all traffic leaving that interface.
Step 15

end
or

commit
Example:

RP/0/RSP0/CPU0:router(config-if)# end
or

RP/0/RSP0/CPU0:router(config-if)# commit
Saves configuration changes.

•When you issue the end command, the system prompts you to commit changes:
Uncommitted changes found, commit them before 
exiting(yes/no/cancel)? 
[cancel]:
–Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

–Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

–Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

•Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.
Step 16

show policy-map interface type interface-path-id [input | output]
Example:

RP/0/RSP0/CPU0:router# show policy-map interface gigabitethernet 0/2/0/0

(Optional) Displays policy configuration information for all classes configured for all service policies on the specified interface.
Configuring Low-Latency Queueing with Strict Priority Queueing

The priority command configures low-latency queueing (LLQ), providing strict priority queueing (PQ). Strict PQ allows delay-sensitive data, such as voice, to be dequeued and sent before packets in other queues are dequeued. When a class is marked as high priority using the priority command, it is required that you configure a policer to limit the priority traffic. This configuration ensures that the priority traffic does not starve all of the other traffic on the line card, which protects low priority traffic from starvation. Use the police command to explicitly configure the policer.

Note Two levels of priority are supported: priority level 1 and priority level 2. If no priority level is configured, the default is priority level 1.

Restrictions

•Within a policy map, you can give one or more classes priority status. When multiple classes within a single policy map are configured as priority classes, all traffic from these classes is queued to the same single priority queue.

SUMMARY STEPS

1. configure

2. policy-map policy-name

3. class class-name

4. police rate {value [units] | percent percentage} [burst burst-size [burst-units]] [peak-burst peak-burst [burst-units]] [peak-rate value [units]]

5. exceed-action action

6. exit

7. priority [level priority-level]

8. exit

9. exit

10. interface type interface-path-id

11. service-policy {input | output} policy-map

12. end
or
commit

13. show policy-map interface type interface-path-id [input | output]

DETAILED STEPS
Command or Action

Purpose

Step 1

configure
Example:

RP/0/RSP0/CPU0:router# configure

Enters global configuration mode.

Step 2

policy-map policy-name
Example:

RP/0/RSP0/CPU0:router(config)# policy-map voice

Enters policy map configuration mode.

•Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy.

Step 3

class class-name
Example:

RP/0/RSP0/CPU0:router(config-pmap)# class voice

Enters policy map class configuration mode.

•Specifies the name of the class whose policy you want to create or change.

Step 4

police rate {value [units] | percent percentage} [burst burst-size [burst-units]] [peak-burst peak-burst [burst-units]] [peak-rate value [units]]
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# police rate 250

Configures traffic policing and enters policy map police configuration mode.

•In this example, the low-latency queue is restricted to 250 kbps to protect low-priority traffic from starvation and to release bandwidth.

Step 5

exceed-action action
Example:

RP/0/RSP0/CPU0:router(config-pmap-c-police)# exceed-action drop

Configures the action to take on packets that exceed the rate limit.

Step 6

Step 7

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap-c-police)# exit

Returns the router to policy map class configuration mode.

Step 8

priority [level priority-level]
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# priority

Specifies priority to a class of traffic belonging to a policy map.

Note If no priority level is configured, the default is priority 1.

Step 9

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# exit

Returns the router to policy map configuration mode.

Step 10

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap)# exit

Returns the router to global configuration mode.

Step 11

interface type interface-path-id
Example:

RP/0/RSP0/CPU0:router(config)# interface gigabitethernet 0/2/0/0

Enters interface configuration mode, and configures an interface.

Step 12

service-policy {input | output} policy-map
Example:

RP/0/RSP0/CPU0:router(config-if)# service-policy output policy1

Attaches a policy map to an input or output interface to be used as the service policy for that interface.

•In this example, the traffic policy evaluates all traffic leaving that interface.
Step 13

end
or

commit
Example:

RP/0/RSP0/CPU0:router(config-if)# end
or

RP/0/RSP0/CPU0:router(config-if)# commit
Saves configuration changes.

•When you issue the end command, the system prompts you to commit changes:
Uncommitted changes found, commit them before 
exiting(yes/no/cancel)? 
[cancel]:
–Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

–Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

–Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

•Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.
Step 14

show policy-map interface type interface-path-id [input | output]
Example:

RP/0/RSP0/CPU0:router# show policy-map interface gigabitethernet 0/2/0/0

(Optional) Displays policy configuration information for all classes configured for all service policies on the specified interface.
Configuring Traffic Shaping

Traffic shaping allows you to control the traffic exiting an interface to match its transmission to the speed of the remote target interface and ensure that the traffic conforms to policies contracted for it.

Shaping performed on incoming and outgoing interfaces is done at the Layer 2 level and includes the Layer 2 header in the rate calculation.

Restrictions

The bandwidth, priority, and shape average commands should not be configured together in the same class.

SUMMARY STEPS

1. configure

2. policy-map policy-name

3. class class-name

4. shape average {percent value | rate [units]}

5. exit

6. exit

7. interface type interface-path-id

8. service-policy {input | output} policy-map

9. end
or
commit

10. show policy-map interface type interface-path-id [input | output]

DETAILED STEPS
Command or Action

Purpose

Step 1

configure
Example:

RP/0/RSP0/CPU0:router# configure

Enters global configuration mode.

Step 2

policy-map policy-name
Example:

RP/0/RSP0/CPU0:router(config)# policy-map policy1

Enters policy map configuration mode.

•Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy.

Step 3

class class-name
Example:

RP/0/RSP0/CPU0:router(config-pmap)# class class1

Enters policy map class configuration mode.

•Specifies the name of the class whose policy you want to create or change.
Step 4
shape average {percent value | rate [units]} 
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# shape average percent 50
Shapes traffic to the indicated bit rate according to average rate shaping in the specified units or as a percentage of the bandwidth.
Step 5

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# exit

Returns the router to policy map configuration mode.

Step 6

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap)# exit

Returns the router to global configuration mode.

Step 7

interface type interface-path-id
Example:

RP/0/RSP0/CPU0:router(config)# interface gigabitethernet 0/2/0/0

Enters interface configuration mode and configures an interface.

Step 8

service-policy {input | output} policy-map
Example:

RP/0/RSP0/CPU0:router(config-if)# service-policy output policy1

Attaches a policy map to an input or output interface to be used as the service policy for that interface.

•In this example, the traffic policy evaluates all traffic leaving that interface.
Step 9

end
or

commit
Example:

RP/0/RSP0/CPU0:router(config-if)# end
or

RP/0/RSP0/CPU0:router(config-if)# commit
Saves configuration changes.

•When you issue the end command, the system prompts you to commit changes:
Uncommitted changes found, commit them before 
exiting(yes/no/cancel)? 
[cancel]:
–Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

–Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

–Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

•Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.
Step 10

show policy-map interface type interface-path-id [input | output]
Example:

RP/0/RSP0/CPU0:router# show policy-map interface gigabitethernet 0/2/0/0

(Optional) Displays policy configuration information for all classes configured for all service policies on the specified interface.
Configuring Traffic Policing

Traffic policing allows you to control the maximum rate of traffic sent or received on an interface.

SUMMARY STEPS

1. configure

2. policy-map policy-name

3. class class-name

4. police rate {value [units] | percent percentage} [burst burst-size [burst-units]] [peak-burst peak-burst [burst-units]] [peak-rate value [units]]

5. conform-action action

6. exceed-action action

7. exit

8. exit

9. exit

10. interface type interface-path-id

11. service-policy {input | output} policy-map

12. end
or
commit

13. show policy-map interface type interface-path-id [input | output]

Note The multi-action set/policer feature allows you to configure multiple conform and exceed actions. Hence, you can repeat the conform-action and exceed-action commands multiple times in your configuration.

DETAILED STEPS
Command or Action

Purpose

Step 1

configure
Example:

RP/0/RSP0/CPU0:router# configure

Enters global configuration mode.

Step 2

policy-map policy-name
Example:

RP/0/RSP0/CPU0:router(config)# policy-map policy1

Enters policy map configuration mode.

•Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy.

Step 3

class class-name
Example:

RP/0/RSP0/CPU0:router(config-pmap)# class class1

Enters policy map class configuration mode.

•Specifies the name of the class whose policy you want to create or change.

Step 4

police rate {value [units] | percent percentage} [burst burst-size [burst-units]] [peak-burst peak-burst [burst-units]] [peak-rate value [units]]
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# police rate 250000

Configures traffic policing and enters policy map police configuration mode. The traffic policing feature works with a token bucket algorithm.

Step 5

conform-action action
Example:

RP/0/RSP0/CPU0:router(config-pmap-c-police)# conform-action set mpls experimental topmost 3

Configures the action to take on packets that conform to the rate limit. The action argument is specified by one of the following keywords:

•drop—Drops the packet.

•set—Has the following keywords and arguments:

–cos value—Sets the class of service value. Range is 0 to 7.

–discard-class value—Sets the discard class value. Range is 0 to 7.

–dscp value—Sets the differentiated services code point (DSCP) value and sends the packet.

–mpls experimental {topmost | imposition} value—Sets the experimental (EXP) value of the Multiprotocol Label Switching (MPLS) packet topmost label or imposed label. Range is 0 to 7.

–precedence precedence—Sets the IP precedence and sends the packet.

–qos-group—Sets the QoS group value. Range is 0 to 63.

•transmit—Transmits the packets.

Step 6

exceed-action action
Example:

RP/0/RSP0/CPU0:router(config-pmap-c-police)# exceed-action set mpls experimental topmost 4

Configures the action to take on packets that exceed the rate limit. The action argument is specified by one of the keywords specified in Step 5.
Step 7
exit
Example:
RP/0/RSP0/CPU0:router(config-pmap-c-police)# 
exit
Returns the router to policy map class configuration mode.
Step 8
exit
Example:
RP/0/RSP0/CPU0:router(config-pmap-c)# exit
Returns the router to policy map configuration mode.
Step 9

exit
Example:

RP/0/RSP0/CPU0:router(config-pmap)# exit

Returns the router to global configuration mode.

Step 10

interface type interface-path-id
Example:

RP/0/RSP0/CPU0:router(config)# interface gigabitethernet 0/5/0/0

Enters configuration mode and configures an interface.

Step 11

service-policy {input | output} policy-map
Example:

RP/0/RSP0/CPU0:router(config-if)# service-policy output policy1

Attaches a policy map to an input or output interface to be used as the service policy for that interface.

•In this example, the traffic policy evaluates all traffic leaving that interface.
Step 12

end
or

commit
Example:

RP/0/RSP0/CPU0:router(config-if)# end
or

RP/0/RSP0/CPU0:router(config-if)# commit
Saves configuration changes.

•When you issue the end command, the system prompts you to commit changes:
Uncommitted changes found, commit them before 
exiting(yes/no/cancel)? 
[cancel]:
–Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

–Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

–Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

•Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.
Step 13

show policy-map interface type interface-path-id [input | output]
Example:

RP/0/RSP0/CPU0:router# show policy-map interface gigabitethernet 0/2/0/0

(Optional) Displays policy configuration information for all classes configured for all service policies on the specified interface.
Configuring Hierarchical Policing

Hierarchical policing provides support at two levels:

•Parent level

•Child level

SUMMARY STEPS

1. configure

2. policy-map policy-name

3. class class-name

4. service-policy policy-map-name

5. police rate percent percentage

6. conform-action action

7. exceed-action action

8. exit

DETAILED STEPS
Command or Action

Purpose

Step 1

configure
Example:

RP/0/RSP0/CPU0:router# configure

Enters global configuration mode.

Step 2

policy-map policy-name
Example:

RP/0/RSP0/CPU0:router(config)# policy-map policy1

Enters policy map configuration mode.

•Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy.

Step 3

class class-name
Example:

RP/0/RSP0/CPU0:router(config-pmap)# class class1

Enters policy map class configuration mode.

•Specifies the name of the class whose policy you want to create or change.

Step 4

service-policy policy-map-name
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# service-policy child

Attaches a policy map to an input or output interface to be used as the service policy for that interface.

Step 5

police rate percent percentage
Example:

RP/0/RSP0/CPU0:router(config-pmap-c)# police rate percent 50

Configures traffic policing and enters policy map police configuration mode.

Step 6

conform-action action
Example:

RP/0/RSP0/CPU0:router(config-pmap-c-police)# conform-action transmit

Configures the action to take on packets that conform to the rate limit. The allowed action is:

transmit—Transmits the packets.

Step 7

exceed-action action
Example:

RP/0/RSP0/CPU0:router(config-pmap-c-police)# exceed-action drop

Configures the action to take on packets that exceed the rate limit. The allowed action is:

drop—Drops the packet.
Step 8

end
or

commit
Example:

RP/0/RSP0/CPU0:router(config-if)# end
or

RP/0/RSP0/CPU0:router(config-if)# commit
Saves configuration changes.

•When you issue the end command, the system prompts you to commit changes:
Uncommitted changes found, commit them before 
exiting(yes/no/cancel)? 
[cancel]:
–Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

–Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

–Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

•Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.
Configuration Examples for Configuring QoS Congestion Management on Cisco ASR 9000 Series Routers

This section provides the following configuration examples:

•Traffic Shaping for an Input Interface: Example

•Traffic Policing for a Bundled Interface: Example

•Hierarchical Policing: Example

•Multi-action Set/Policer: Example

Traffic Shaping for an Input Interface: Example

The following example shows how to configure a policy map on an input interface:
policy-map p2
 class voip
 shape average 20 mbps
!
interface GigabitEthernet0/4/0/24
 service-policy input p2
 commit
RP/0/RSP0/CPU0:Jun 8 16:55:11.819 : config[65546]: %MGBL-LIBTARCFG-6-COMMIT : 
Configuration committed by user 'cisco'. Use 'show configuration commit changes 
1000006140' to view the changes. 
The following example shows the display output for the previous policy map configuration:
RP/0/RSP0/CPU0:router# show policy-map interface GigabitEthernet 0/4/0/24 input 
GigabitEthernet0/4/0/24 input: p2
  Class voip
    Classification statistics                      (packets/bytes)      (rate - kbps)
            Matched       :                               0/0                     0
            Transmitted   :                               0/0                     0
            Total Dropped :                               0/0                     0
Queueing statistics
            Queue ID                                 : 268435978
            High watermark  (Unknown)
            Inst-queue-len  (packets)                : 0
            Avg-queue-len   (Unknown)
            Taildropped(packets/bytes)               : 0/0
            Queue(confirm)       :                      0/0
            Queue(exceed)        :                      0/0
            RED random drops(packets/bytes)          : 0/0
Class class-default
  Classification statistics               (packets/bytes)      (rate - kbps)
          Matched        :                     : 0/0                     0
            Transmitted    : Un-determined
            Total Dropped  : Un-determined
Traffic Policing for a Bundled Interface: Example

The following example shows how to configure a policy map for a bundled interface:
policy-map p2
 class voip
 police rate percent 20
 commit
RP/0/RSP0/CPU0:Jun  8 16:51:51.679 : config[65546]: %MGBL-LIBTARCFG-6-COMMIT : 
Configuration committed by user 'cisco'.   Use 'show configuration commit changes 
1000006135' to view the changes.
 exit
exit  
interface bundle-ether 1
 service-policy input p2
 commit
RP/0/RSP0/CPU0:Jun  8 16:52:02.650 : config[65546]: %MGBL-LIBTARCFG-6-COMMIT : 
Configuration committed by user 'cisco'.   Use 'show configuration commit changes 
1000006136' to view the changes. 
The following example shows the display output for the successful policy map configuration in which policing was configured in percentage:
RP/0/RSP0/CPU0:router# show policy-map interface bundle-ether 1
Bundle-ether1 input: p2
  Class voip
    Classification statistics                      (packets/bytes)      (rate - kbps)
            Matched                              : 0/0      0
    Policing statistics                            (packets/bytes)      (rate - kbps)
            Policed(conform)                     : 0/0   0
            Policed(exceed)                      : 0/0   0
            Policed(violate)                     : 0/0   0
            Policed and dropped                  : 0/0
  Class default
    Classification statistics                      (packets/bytes)      (rate - kbps)
            Matched                              : 0/0      0
            Transmitted                          : 0/0      0
            Total Dropped                        : 0/0      0
    Queueing statistics
            Vital           (packets)            : 0
    Queueing statistics
            Queue ID                             : 36
            High watermark  (packets)            : 0
            Inst-queue-len  (bytes)              : 0
            Avg-queue-len   (bytes)              : 0
            TailDrop Threshold(bytes)            : 239616000
            Taildropped(packets/bytes)           : 0/0
Hierarchical Policing: Example

The following configuration is an example of typical hierarchical policing:
policy-map parent
     class class-default
       police rate 10 mbps
         service-policy child
!
policy-map child
     class class-default
       police rate percent 50
        conform-action transmit
        exceed-action drop
Multi-action Set/Policer: Example

The following example shows how to configure multi-action set/policer in the ingress direction:
policy-map child
 class 3play-video
  police rate 3125000 peak-rate 100000000 peak-burst 3125000
    conforfm-action set mpls exp imp 1
   conform-action set discard-class 1
Additional References

The following sections provide references related to implementing QoS congestion management.

Related Documents

Related Topic

Document Title

Initial system bootup and configuration

Cisco ASR 9000 Series Aggregation Services Router Getting Started Guide

Master command reference

Cisco ASR 9000 Series Aggregation Services Router Master Command Listing

QoS commands

Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Command Reference

User groups and task IDs

"Configuring AAA Services on Cisco ASR 9000 Series Router" module of Cisco Cisco ASR 9000 Series Aggregation Services Router System Security Configuration Guide

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