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Marking Network Traffic

Table Of Contents

Marking Network Traffic

Finding Feature Information

Contents

Prerequisites for Marking Network Traffic

Restrictions for Marking Network Traffic

Information About Marking Network Traffic

Purpose of Marking Network Traffic

Benefits of Marking Network Traffic

Two Methods for Marking Traffic Attributes

Method One: Using a set Command

Method Two: Using a Table Map

Traffic Marking Procedure Flowchart

MQC and Network Traffic Marking

Traffic Classification Compared with Traffic Marking

How to Mark Network Traffic

Creating a Class Map for Marking Network Traffic

Creating a Table Map for Marking Network Traffic

Creating a Policy Map for Applying a QoS Feature to Network Traffic

Restrictions

What to Do Next

Attaching the Policy Map to an Interface

Configuring QoS When Using IPsec VPNs

Restrictions

Configuration Examples for Marking Network Traffic

Example: Creating a Class Map for Marking Network Traffic

Example: Creating a Table Map for Marking Network Traffic

Example: Creating a Policy Map for Applying a QoS Feature to Network Traffic

Example: Attaching the Policy Map to an Interface

Example: Configuring QoS When Using IPsec VPNs

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for Marking Network Traffic


Marking Network Traffic


First Published: May 02, 2005
Last Updated: July 23, 2010

Marking network traffic allows you to set or modify the attributes for traffic (that is, packets) belonging to a specific class or category. When used in conjunction with network traffic classification, marking network traffic is the foundation for enabling many quality of service (QoS) features on your network. This module contains conceptual information and the configuration tasks for marking network traffic.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for Marking Network Traffic" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

Prerequisites for Marking Network Traffic

Restrictions for Marking Network Traffic

Information About Marking Network Traffic

How to Mark Network Traffic

Configuration Examples for Marking Network Traffic

Additional References

Feature Information for Marking Network Traffic

Prerequisites for Marking Network Traffic

In order to mark network traffic, Cisco Express Forwarding must be configured on both the interface receiving the traffic and the interface sending the traffic.

Restrictions for Marking Network Traffic

Traffic marking can be configured on an interface, a subinterface, or an ATM permanent virtual circuit (PVC). Marking network traffic is not supported on the following interfaces:

Any interface that does not support Cisco Express Forwarding

ATM switched virtual circuit (SVC)

Fast EtherChannel

PRI

Tunnel

Information About Marking Network Traffic

Purpose of Marking Network Traffic

Benefits of Marking Network Traffic

Two Methods for Marking Traffic Attributes

MQC and Network Traffic Marking

Traffic Classification Compared with Traffic Marking

Purpose of Marking Network Traffic

Traffic marking is a method used to identify certain traffic types for unique handling, effectively partitioning network traffic into different categories.

After the network traffic is organized into classes by traffic classification, traffic marking allows you to mark (that is, set or change) a value (attribute) for the traffic belonging to a specific class. For instance, you may want to change the class of service (CoS) value from 2 to 1 in one class, or you may want to change the differentiated services code point (DSCP) value from 3 to 2 in another class. In this module, these values are referred to as attributes.

Attributes that can be set and modified include the following:

Cell loss priority (CLP) bit

CoS value of an outgoing packet

Discard eligible (DE) bit setting in the address field of a Frame Relay frame

Discard-class value

DSCP value in the type of service (ToS) byte

MPLS EXP field value in the topmost label on either an input or an output interface

Multiprotocol Label Switching (MPLS) experimental (EXP) field on all imposed label entries

Precedence value in the packet header

QoS group identifier (ID)

ToS bits in the header of an IP packet

Benefits of Marking Network Traffic

Improved Network Performance

Traffic marking allows you to fine-tune the attributes for traffic on your network. This increased granularity helps single out traffic that requires special handling, and thus, helps to achieve optimal application performance.

Traffic marking allows you to determine how traffic will be treated, based on how the attributes for the network traffic are set. It allows you to segment network traffic into multiple priority levels or classes of service based on those attributes, as follows:

Traffic marking is often used to set the IP precedence or IP DSCP values for traffic entering a network. Networking devices within your network can then use the newly marked IP precedence values to determine how traffic should be treated. For example, voice traffic can be marked with a particular IP precedence or DSCP and low latency queuing (LLQ) can then be configured to put all packets of that mark into a priority queue. In this case, the marking was used to identify traffic for LLQ.

Traffic marking can be used to identify traffic for any class-based QoS feature (any feature available in policy-map class configuration mode, although some restrictions exist).

Traffic marking can be used to assign traffic to a QoS group within a router. The router can use the QoS groups to determine how to prioritize traffic for transmission. The QoS group value is usually used for one of the two following reasons:

To leverage a large range of traffic classes. The QoS group value has 100 different individual markings, as opposed to DSCP and Precedence, which have 64 and 8, respectively.

If changing the Precedence or DSCP value is undesirable.

If a packet (for instance, in a traffic flow) needs to be marked to differentiate user-defined QoS services is leaving a router and entering a switch, the router can set the CoS value of the traffic, because the switch can process the Layer 2 CoS header marking. Alternatively, the Layer 2 CoS value of the traffic leaving a switch can be mapped to the Layer 3 IP or MPLS value.

Weighted random early detection (WRED) uses precedence values or DSCP values to determine the probability that the traffic will be dropped. Therefore, the Precedence and DSCP can be used in conjunction with WRED.

Two Methods for Marking Traffic Attributes

There are two methods for specifying and marking traffic attributes:

You can specify and mark the traffic attribute by using a set command.

With this method, you configure individual set commands for the traffic attribute that you want to mark.

You can specify and mark the traffic attribute by creating a mapping table (called a "table map").

With this method, you configure the traffic attributes that you want to mark once in a table map and then the markings can be propagated throughout the network.

These methods are further described in the sections that follow.

Method One: Using a set Command

You specify the traffic attribute you want to change with a set command configured in a policy map. Table 1 lists the available set commands and the corresponding attribute. Table 1 also includes the network layer and the network protocol typically associated with the traffic attribute.

Table 1 set Commands and Corresponding Traffic Attribute, Network Layer, and Protocol

set Commands 1
Traffic Attribute
Network Layer
Protocol

set atm-clp

CLP bit

Layer 2

ATM

set cos

Layer 2 CoS value of the outgoing traffic

Layer 2

ATM, Frame Relay

set discard-class

discard-class value

Layer 2

ATM, Frame Relay

set dscp

DSCP value in the ToS byte

Layer 3

IP

set fr-de

DE bit setting in the address field of a Frame Relay frame

Layer 2

Frame Relay

set ip tos (route-map)

ToS bits in the header of an IP packet

Layer 3

IP

set mpls experimental imposition

MPLS EXP field on all imposed label entries

Layer 3

MPLS

set mpls experimental topmost

MPLS EXP field value in the topmost label on either an input or an output interface

Layer 3

MPLS

set precedence

precedence value in the packet header

Layer 3

IP

set qos-group

QoS group ID

Layer 3

IP, MPLS

1 Cisco IOS set commands can vary by release. For more information, see the command documentation for the Cisco IOS release that you are using


If you are using individual set commands, those set commands are specified in a policy map. The following is a sample of a policy map configured with one of the set commands listed in Table 3.

In this sample configuration, the set atm-clp command has been configured in the policy map (policy1) to mark the CLP attribute.

 policy-map policy1
  class class1
  set atm-clp
  end

Method Two: Using a Table Map

You can create a table map that can be used to mark traffic attributes. A table map is a kind of two-way conversion chart that lists and maps one traffic attribute to another. A table map supports a many-to-one type of conversion and mapping scheme. The table map establishes a to-from relationship for the traffic attributes and defines the change to be made to the attribute. That is, an attribute is set to one value that is taken from another value. The values are based on the specific attribute being changed. For instance, the Precedence attribute can be a number from 0 to 7, while the DSCP attribute can be a number from 0 to 63.

The following is a sample table map configuration:

table-map table-map1

 map from 0 to 1

 map from 2 to 3

 exit


Table 2 lists the traffic attributes for which a to-from relationship can be established using the table map.

Table 2 Traffic Attributes for Which a To-From Relationship Can Be Established

The "To" Attribute
The "From" Attribute

Precedence

CoS

QoS group

DSCP

CoS

QoS group

CoS

Precedence

DSCP

QoS group

Precedence

DSCP

MPLS EXP topmost

MPLS EXP topmost

QoS group

MPLS EXP imposition

Precedence

DSCP


Once the table map is created, you configure a policy map to use the table map. In the policy map, you specify the table map name and the attributes to be mapped by using the table keyword and the table-map-name argument with one of the commands listed in Table 3.

Table 3 Commands Used in Policy Maps to Map Attributes 

Command Used in Policy Maps
Maps These Attributes

set cos dscp table table-map-name

CoS to DSCP

set cos precedence table table-map-name

CoS to Precedence

set dscp cos table table-map-name

DSCP to CoS

set dscp qos-group table table-map-name

DSCP to qos-group

set mpls experimental imposition dscp table table-map-name

MPLS EXP imposition to DSCP

set mpls experimental imposition precedence table table-map-name

MPLS EXP imposition to precedence

set mpls experimental topmost qos-group table table-map-name

MPLS EXP topmost to QoS-group

set precedence cos table table-map-name

Precedence to CoS

set precedence qos-group table table-map-name

Precedence to QoS-group

set qos-group dscp table table-map-name

QoS-group to DSCP

set qos-group mpls exp topmost table table-map-name

QoS-group to MPLS EXP topmost

set qos-group precedence table table-map-name

QoS-group to Precedence


The following is an example of a policy map (policy2) configured to use the table map (table-map1) created earlier:

policy map policy2

 class class-default

 set cos dscp table table-map1

 exit


In this example, a mapping relationship was created between the CoS attribute and the DSCP attribute as defined in the table map.

Traffic Marking Procedure Flowchart

Figure 1 illustrates the order of the procedures for configuring traffic marking.

Figure 1 Traffic Marking Procedure Flowchart

MQC and Network Traffic Marking

To configure network traffic marking, you use the Modular Quality of Service (QoS) Command-Line Interface (CLI) (MQC).

The MQC is a CLI structure that allows you to complete the following tasks:

Specify the matching criteria used to define a traffic class.

Create a traffic policy (policy map). The traffic policy defines the QoS policy actions to be taken for each traffic class.

Apply the policy actions specified in the policy map to an interface, subinterface, or ATM PVC by using the service-policy command.

Traffic Classification Compared with Traffic Marking

Traffic classification and traffic marking are closely related and can be used together. Traffic marking can be viewed as an additional action, specified in a policy map, to be taken on a traffic class.

Traffic classification allows you to organize into traffic classes on the basis of whether the traffic matches specific criteria. For example, all traffic with a CoS value of 2 is grouped into one class, and traffic with DSCP value of 3 is grouped into another class. The match criterion is user-defined.

After the traffic is organized into traffic classes, traffic marking allows you to mark (that is, set or change) an attribute for the traffic belonging to that specific class. For instance, you may want to change the CoS value from 2 to 1, or you may want to change the DSCP value from 3 to 2.

The match criteria used by traffic classification are specified by configuring a match command in a class map. The marking action taken by traffic marking is specified by configuring a set command in a policy map. These class maps and policy maps are configured using the MQC.

Table 4 compares the features of traffic classification and traffic marking.

Table 4 Traffic Classification Compared with Traffic Marking

 
Traffic Classification
Traffic Marking
Goal

Groups network traffic into specific traffic classes on the basis of whether the traffic matches the user-defined criterion.

After the network traffic is grouped into traffic classes, modifies the attributes for the traffic in a particular traffic class.

Configuration Mechanism

Uses class maps and policy maps in the MQC.

Uses class maps and policy maps in the MQC.

CLI

In a class map, uses match commands (for example, match cos) to define the traffic matching criterion.

Uses the traffic classes and matching criterion specified by traffic classification.

In addition, uses set commands (for example, set cos) in a policy map to modify the attributes for the network traffic.

If a table map was created, uses the table keyword and table-map-name argument with the set commands (for example, set cos precedence table table-map-name) in the policy map to establish the to-from relationship for mapping attributes.


How to Mark Network Traffic

Creating a Class Map for Marking Network Traffic


Note The match fr-dlci command is included in the steps below. The match fr-dlci command is just an example of one of the match commands that can be used. See the command documentation for the Cisco IOS release that you are using for a complete list of match commands.


SUMMARY STEPS

1. enable

2. configure terminal

3. class-map class-map-name [match-all | match-any]

4. match fr-dlci dlci-number

5. end

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

class-map class-map-name [match-all | match-any]

Example:

Router(config)# class-map class1

Creates a class map to be used for matching traffic to a specified class and enters class-map configuration mode.

Enter the class map name.

Step 4 

match fr-dlci dlci-number

Example:

Router(config-cmap)# match fr-dlci 500

(Optional) Specifies the Frame Relay DLCI number as a match criterion in a class map.

Note The match fr-dlci command classifies traffic on the basis of the Frame Relay DLCI number. The match fr-dlci command is just an example of one of the match commands that can be used. The match commands vary by Cisco IOS release. See the command documentation for the Cisco IOS release that you are using for a complete list of match commands.

Step 5 

end

Example:

Router(config-cmap)# end

(Optional) Returns to privileged EXEC mode.

Creating a Table Map for Marking Network Traffic


Note If you are not using a table map, skip this procedure and advance to "Creating a Policy Map for Applying a QoS Feature to Network Traffic" section.


SUMMARY STEPS

1. enable

2. configure terminal

3. table-map table-map-name map from from-value to to-value [default default-action-or-value]

4. end

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

table-map table-map-name map from from-value to to-value [default default-action-or-value]


Example:

Router(config)# table-map table-map1 map from 2 to 1

Creates a table map using the specified name and enters tablemap configuration mode.

Enter the name of the table map you want to create.

Enter each value mapping on a separate line. Enter as many separate lines as needed for the values you want to map.

The default keyword and default-action-or-value argument set the default value (or action) to be used if a value is not explicitly designated.

Step 4 

end

Example:

Router(config-tablemap)# end

(Optional) Exits tablemap configuration mode and returns to privileged EXEC mode.

Creating a Policy Map for Applying a QoS Feature to Network Traffic

Restrictions

The set atm-clp command is supported on the following adapters only:

Enhanced ATM Port Adapter (PA-A3)

ATM Inverse Multiplexer over ATM Port Adapter with 8 T1 Ports (PA-A3-8T1IMA)

ATM Inverse Multiplexer over ATM Port Adapter with 8 E1 Ports (PA-A3-8E1IMA)

Before modifying the encapsulation type from IEEE 802.1 Q to ISL, or vice versa, on a subinterface, detach the policy map from the subinterface. After changing the encapsulation type, reattach the policy map.

A policy map containing the set qos-group command can only be attached as an input traffic policy. QoS group values are not usable for traffic leaving a router.

A policy map containing the set cos command can only be attached as an output traffic policy.

A policy map containing the set atm-clp command can be attached as an output traffic policy only. The set atm-clp command does not support traffic that originates from the router.


Note The set cos command and set cos dscp table table-map-name command are shown in the steps that follow. The set cos command and set cos dscp table table-map-name command are examples the set commands that can be used when marking traffic. Other set commands can be used. For a list of other set commands, see Table 1 and Table 3.


SUMMARY STEPS

1. enable

2. configure terminal

3. policy-map policy-map-name

4. class {class-name | class-default}

5. set cos cos-value

or

set cos dscp table table-map-name

6. end

7. show policy-map

or

show policy-map policy-map class class-name

8. exit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

policy-map policy-map-name

Example:

Router(config)# policy-map policy1

Specifies the name of the policy map created earlier and enters policy-map configuration mode.

Enter the policy map name.

Step 4 

class {class-name | class-default}

Example:

Router(config-pmap)# class class1

Specifies the name of the class whose policy you want to create and enters policy-map class configuration mode. This class is associated with the class map created earlier.

Enter the name of the class or enter the class-default keyword.

Step 5 

set cos cos-value


(Optional) Sets the CoS value in the type of service (ToS) byte.

Note The set cos command is an example of one of the set commands that can be used when marking traffic. Other set commands can be used. For a list of other set commands, see Table 1.

 

or

or

 

set cos dscp table table-map-name


(Optional) If a table map has been created earlier, sets the CoS value based on the DSCP value (or action) defined in the table map.

Note The set cos dscp table table-map-name command is an example of one of the commands that can be used. For a list of other commands, see Table 3.

 
Example:

Router(config-pmap-c)# set cos 2

 
 

or

 
 
Example:

Router(config-pmap-c)# set cos dscp table table-map1

 

Step 6 

end

Example:

Router(config-pmap-c)# end

Returns to privileged EXEC mode.

Step 7 

show policy-map

(Optional) Displays all configured policy maps.

 

or

or

 

show policy-map policy-map class class-name


(Optional) Displays the configuration for the specified class of the specified policy map.

Enter the policy map name and the class name.

 
Example:

Router# show policy-map

 
 

or

 
 
Example:

Router# show policy-map policy1 class class1

 

Step 8 

exit

Example:

Router# exit

(Optional) Exits privileged EXEC mode.

What to Do Next

Create and configure as many policy maps as you need for your network. To create and configure additional policy maps, repeat the steps in the "Creating a Policy Map for Applying a QoS Feature to Network Traffic" section. Then attach the policy maps to the appropriate interface, following the instructions in the "Attaching the Policy Map to an Interface" section.

Attaching the Policy Map to an Interface


Note Depending on the needs of your network, policy maps can be attached to an interface, a subinterface, or an ATM permanent virtual circuit (PVC).


SUMMARY STEPS

1. enable

2. configure terminal

3. interface type number [name-tag]

4. pvc [name] vpi/vci [ilmi | qsaal | smds | l2transport]

5. exit

6. service-policy {input | output} policy-map-name

7. end

8. show policy-map interface interface-name

9. exit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

interface type number [name-tag]

Example:

Router(config)# interface serial4/0

Configures an interface type and enters interface configuration mode.

Enter the interface type and number.

Step 4 

pvc [name] vpi/vci [ilmi |qsaal |smds | l2transport]

Example:

Router(config-if)# pvc cisco 0/16

(Optional) Creates or assigns a name to an ATM permanent virtual circuit (PVC), specifies the encapsulation type on an ATM PVC, and enters ATM virtual circuit configuration mode.

Enter the PVC name, the ATM network virtual path identifier, and the network virtual channel identifier.

Note This step is required only if you are attaching the policy map to an ATM PVC. If you are not attaching the policy map to an ATM PVC, advance to Step 6.

Step 5 

exit

Example:

Router(config-atm-vc)# exit

(Optional) Returns to interface configuration mode.

Note This step is required only if you are attaching the policy map to an ATM PVC and you completed Step 4. If you are not attaching the policy map to an ATM PVC, advance to Step 6.

Step 6 

service-policy {input | output} policy-map-name

Example:

Router(config-if)# service-policy input policy1

Attaches a policy map to an input or output interface.

Enter the policy map name.

Note Policy maps can be configured on ingress or egress routers. They can also be attached in the input or output direction of an interface. The direction (input or output) and the router (ingress or egress) to which the policy map should be attached varies according your network configuration. When using the service-policy command to attach the policy map to an interface, be sure to choose the router and the interface direction that are appropriate for your network configuration.

Step 7 

end

Example:

Router(config-if)# end

Returns to privileged EXEC mode.

Step 8 

show policy-map interface type number

Example:

Router# show policy-map interface serial4/0

(Optional) Displays traffic statistics of all classes configured for all service policies on the specified interface, subinterface, or PVC on the interface.

When there are multiple instances of the same class in a policy-map, and this policy-map is attached to an interface,

show policy-map interface <interface_name> output class <class-name>


returns only the first instance.

Enter the interface type and number.

Step 9 

exit

Example:

Router# exit

(Optional) Exits privileged EXEC mode.

Configuring QoS When Using IPsec VPNs


Note This task is required only if you are using IPsec Virtual Private Networks (VPNs). Otherwise, this task is not necessary. For information about IPsec VPNs, see the "Configuring Security for VPNs with IPsec" module.


Restrictions

This task uses the qos pre-classify command to enable QoS preclassification for the packet. QoS preclassification is not supported for all fragmented packets. If a packet is fragmented, each fragment might received different preclassifications.

SUMMARY STEPS

1. enable

2. configure terminal

3. crypto map map-name seq-num

4. exit

5. interface type number [name-tag]

6. qos pre-classify

7. end

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

crypto map map-name seq-num

Example:

Router(config)# crypto map mymap 10

Enters crypto map configuration mode and creates or modifies a crypto map entry.

Enter the crypto map name and sequence number.

Step 4 

exit

Example:

Router(config-crypto-map)# exit

Returns to global configuration mode.

Step 5 

interface type number [name-tag]

Example:

Router(config)# interface serial4/0

Configures an interface type and enters interface configuration mode.

Enter the interface type and number.

Step 6 

qos pre-classify

Example:

Router(config-if)# qos pre-classify

Enables QoS preclassification.

Step 7 

end

Example:

Router(config-if)# end

(Optional) Exits interface configuration mode and returns to privileged EXEC mode.

Configuration Examples for Marking Network Traffic

Example: Creating a Class Map for Marking Network Traffic

The following is an example of creating a class map to be used for marking network traffic. In this example, a class called class1 has been created. The traffic with a Frame Relay DLCI value of 500 will be put in this class.

Router> enable

Router# configure terminal

Router(config)# class-map class1

Router(config-cmap)# match fr-dlci 500

Router(config-cmap)# end


Example: Creating a Table Map for Marking Network Traffic

In the following example, the table-map (value mapping) command has been used to create and configure a table map called table-map1. This table map will be used to establish a to-from relationship between one traffic-marking value and another.

In table-map1, a traffic-marking value of 0 will be mapped to a value of 1.

Router> enable
Router# configure terminal
Router(config)# table-map table-map1 map from 0 to 1

Router(config-tablemap)# end


Example: Creating a Policy Map for Applying a QoS Feature to Network Traffic

Policy Map Configured to Use set Command

The following is an example of creating a policy map to be used for traffic marking. In this example, a policy map called policy1 has been created, and the set dscp command has been configured for class1.

Router> enable
Router# configure terminal
Router(config)# policy-map policy1
Router(config-pmap)# class class1
Router(config-pmap-c)# set dscp 2
Router(config-pmap-c)# end

Policy Map Configured to Use a Table Map

A policy map called policy1 has been created and configured to use table-map1 for setting the precedence value. In this example, the CoS value will be set according to the DSCP value defined in table-map1 created previously.

Router(config)# policy map policy1

Router(config-pmap)# class class-default

Router(config-pmap-c)# set cos dscp table table-map1

Router(config-pmap-c)# end


Note As an alternative to configuring the set cos dscp table table-map1 command shown in the example, you could configure the command without specifying the table keyword and the applicable table-map-name argument (that is, you could configure the set cos dscp command). When the command is configured without the table keyword and applicable table map name, the values are copied from the specified categories. In this case, the DSCP value is copied and used to set the CoS value.

When the DSCP value is copied and used for the CoS value only the first 3 bits (that is, the class selector bits) of the DSCP value will be used to set the CoS value. For example, if the DSCP value is EF (101110), the first 3 bits of this DSCP value will be used to set the CoS value, resulting in a CoS value of 5 (101).


Policy Map Configured to Use a Table Map for Mapping MPLS EXP Values

This section contains an example of a policy map configured to map MPLS experimental (EXP) values. Figure 2 illustrates the network topology for this configuration example.

Figure 2 Network Topology for Mapping MPLS EXP Value

For this configuration example, traffic arrives at the input interface (an Ethernet 1/0 interface) of the ingress label edge router (LER). The precedence value is copied and used as the MPLS EXP value of the traffic when the MPLS label is imposed. This label imposition takes place at the ingress LER.

The traffic leaves the ingress LER through the output interface (an Ethernet 2/0 interface), traverses through the network backbone into the MPLS cloud, and enters the egress LER.

At the input interface of the egress LER (an Ethernet 3/0 interface), the MPLS EXP value is copied and used as the QoS group value. At the output interface of the egress LER (an Ethernet 4/0 interface), the QoS group value is copied and used as the precedence value.

To accomplish configuration described above, three separate policy maps were required—policy1, policy2, and policy3. Each policy map is configured to convert and propagate different traffic-marking values.

The first policy map, policy1, is configured to copy the precedence value of the traffic and use it as the MPLS EXP value during label imposition.

Router(config)# policy-map policy1

Router(config-pmap)# class class-default

Router(config-pmap-c)# set mpls experimental imposition precedence

Router(config-pmap-c)# end


When the traffic leaves the LER through the output interface (the Ethernet 2/0 interface), the MPLS EXP value is copied from the precedence value during MPLS label imposition. Copying the MPLS EXP value from the precedence value ensures that the MPLS EXP value reflects the appropriate QoS treatment. The traffic now proceeds through the MPLS cloud into the egress LER.

A second policy map called policy2 has been configured to copy the MPLS EXP value in the incoming MPLS traffic to the QoS group value. The QoS group value is used for internal purposes only. The QoS group value can be used with output queueing on the output interface of the egress router. The QoS group value can also be copied and used as the precedence value, as traffic leaves the egress LER through the output interface (the Ethernet 4/0 interface).

Router(config)# policy-map policy2

Router(config-pmap)# class class-default

Router(config-pmap-c)# set qos-group mpls experimental topmost

Router(config-pmap-c)# end


A third policy map called policy3 has been configured to copy the internal QoS group value (previously based on the MPLS EXP value) to the precedence value. The QoS group value will be copied to the precedence value as the traffic leaves the egress LER through the output interface.

Router(config)# policy-map policy3

Router(config-pmap)# class class-default

Router(config-pmap-c)# set precedence qos-group

Router(config-pmap-c)# end


Configuring these policy maps as shown (and attaching them to interfaces as shown in "Example: Attaching the Policy Map to an Interface" section), causes the appropriate quality of service treatment to be preserved for the traffic as the traffic progresses along an IP network, through an MPLS cloud, and back again into an IP network.


Note This configuration could also have been accomplished by first creating a table map (used to map one value to another) and then specifying the table keyword and table-map-name argument in each of the set commands (for example, set precedence qos-group table tablemap1).

In the MPLS configuration example, a table map was not created, and the set commands were configured without specifying the table keyword and table-map-name argument (for example, set precedence qos-group).

When the set commands are configured without specifying the table keyword and table-map-name argument, the values are copied from the specified categories. In this case, the QoS group value was copied and used to set the precedence value.

When the DSCP value is copied and used for the MPLS EXP value, only the first 3 bits (that is, the class selector bits) of the DSCP value will be used to set the MPLS value.


Example: Attaching the Policy Map to an Interface

The following is an example of attaching the policy map to the interface. In this example, the policy map called policy1 has been attached in the input direction of the Serial4/0 interface.

Router> enable
Router# configure terminal
Router(config)# interface serial4/0
Router(config-if)# service-policy input policy1 
Router(config-if)# end

Example: Configuring QoS When Using IPsec VPNs

The following is an example of configuring QoS when using IPsec VPNs. In this example, the crypto map command specifies the IPsec crypto map (mymap 10) to which the qos pre-classify command will be applied.

Router> enable
Router# configure terminal
Router(config)# crypto map mymap 10 
Router(config-crypto-map)# qos pre-classify
Router(config-crypto-map)# exit

Additional References

Related Documents

Related Topic
Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

QoS commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

Cisco IOS Quality of Service Solutions Command Reference

MQC

"Applying QoS Features Using the MQC" module

Cisco Express Forwarding

"Cisco Express Forwarding Features Roadmap" module

Classifying network traffic

"Classifying Network Traffic" module

IPsec and VPNs

"Configuring Security for VPNs with IPsec" module

Committed Access Rate (CAR)

"Configuring Committed Access Rate" module


Standards

Standard
Title

No new or modified standards are supported, and support for existing standards has not been modified.


MIBs

MIB
MIBs Link

No new or modified MIBs are supported, and support for existing MIBs has not been modified.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs


RFCs

RFC
Title

No new or modified RFCs are supported, and support for existing RFCs has not been modified.


Technical Assistance

Description
Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html


Feature Information for Marking Network Traffic

Table 5 lists the features in this module.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.


Note Table 5 lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Table 5 Feature Information for Marking Network Traffic 

Feature Name
Software Releases
Feature Configuration Information

Enhanced Packet Marking

12.2(13)T

The Enhanced Packet Marking feature allows you to map and convert the marking of a packet from one value to another by using a kind of conversion chart called a table map. The table map establishes an equivalency from one value to another. For example, the table map can map and convert the class of service (CoS) value of a packet to the precedence value of the packet. This value mapping can be propagated for use on the network, as needed.

The following sections provide information about this feature:

Information About Marking Network Traffic

How to Mark Network Traffic

QoS Packet Marking

12.2(8)T

The QoS Packet Marking feature allows you to mark packets by setting the IP precedence bit or the IP differentiated services code point (DSCP) in the Type of Service (ToS) byte, and associate a local QoS group value with a packet.

The following sections provide information about this feature:

Information About Marking Network Traffic

How to Mark Network Traffic

Class-Based Marking

12.2(2)T

The Class-Based Packet Marking feature provides users with a user-friendly command-line interface (CLI) for efficient packet marking by which users can differentiate packets based on the designated markings.

The following sections provide information about this feature:

Information About Marking Network Traffic

How to Mark Network Traffic

Quality of Service for Virtual Private Networks

12.2(2)T

The QoS for VPNs feature provides a solution for making Cisco IOS QoS services operate in conjunction with tunneling and encryption on an interface. Cisco IOS software can classify packets and apply the appropriate QoS service before the data is encrypted and tunneled. The QoS for VPN feature allows users to look inside the packet so that packet marking can be done based on original port numbers and based on source and destination IP addresses. This allows the service provider to treat mission critical or multi-service traffic with higher priority across their network.

The following sections provide information about this feature:

Configuring QoS When Using IPsec VPNs

Example: Configuring QoS When Using IPsec VPNs

ATM Cell Loss Priority (CLP) Setting

Class-Based Ethernet CoS Matching and Marking (802.1p and ISL CoS)

Class-Based Marking

Custom Queueing (CQ)

PXF Based Frame Relay DE Bit Marking

QoS Packet Marking

15.0(1)S

The ATM Cell Loss Priority (CLP) Setting, Class-Based Ethernet CoS Matching and Marking (802.1p and ISL CoS), Class-Based Marking, Custom Queueing (CQ), PXF Based Frame Relay DE Bit Marking, QoS Packet Marking and features were integrated into theCisco IOS Release 15.0(1)S release.