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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.
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and 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 table.
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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.
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:
Discard-class value
DSCP value in the type of service (ToS) byte
MPLS EXP field value in the topmost label on an input 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
For information on attributes that marking supports see, Quality of Service Configuration Guidelines for Cisco ASR 900 Series.
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 a queueing mechanism can then be configured to put all packets of that mark into a priority queue.
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).
Note | The QoS group range is from 0 to 7 on the Cisco RSP3 Module. |
If a packet (for instance, in a traffic flow) that needs to be marked to differentiate user-defined QoS services is leaving a device and entering a switch, the device 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.
Note | The mapping of Layer 2 CoS value of the traffic to the Layer 3 IP or MPLS value is not supported on the Cisco RSP3 Module. |
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.
There are two methods for specifying and marking traffic attributes:
With this method, you configure individual set commands for the traffic attribute that you want to mark.
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.
Note | Marking using table-map is not supported on the Cisco RSP3 Module. |
These methods are further described in the sections that follow.
You specify the traffic attribute that you want to change with a setcommand configured in a policy map. The table below lists the available setcommands and the corresponding attribute. The table also includes the network layer and the network protocol typically associated with the traffic attribute.
set Commands1 |
Traffic Attribute |
Network Layer |
Protocol |
||
---|---|---|---|---|---|
set cos |
Layer 2 CoS value of the outgoing traffic |
Layer 2 |
|||
set discard-class |
discard-class value |
|
|||
set dscp |
DSCP value in the ToS byte |
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 |
Note | The set qos-group can be used for L2 traffic on the Cisco ASR 900 RSP3 Module. |
policy-map policy1 class class1 set dscp 1 end
Note | set dscp command is not supported on the Cisco ASR 900 RSP3 Module for L2 EFP configuration. |
The figure below illustrates the order of the procedures for configuring traffic marking.
You specify and mark the traffic attribute that you want to change by using a set command configured in a policy map.
With this method, you configure individual set commands for the traffic attribute that you want to mark.
The table below lists the available set commands and the corresponding attribute. The table below also includes the network layer and the network protocol typically associated with the traffic attribute.
set Commands2 |
Traffic Attribute |
Network Layer |
Protocol |
---|---|---|---|
set cos |
Layer 2 CoS value of the outgoing traffic |
Layer 2 |
|
set discard-class |
discard-class value |
Layer 2 |
|
set dscp |
DSCP value in the ToS byte |
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 an input or 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 |
If you are using individual set commands, those set commands are specified in a policy map. The following is a sample policy map configured with one of the set commands listed in the table above. In this sample configuration, the set cos command has been configured in the policy map (policy1) to mark the CoS value.
policy-map policy1 class class1 set cos 1 end
For information on configuring a policy map, see the “Creating a Policy Map for Applying a QoS Feature to Network Traffic” section.
The final task is to attach the policy map to the interface. For information on attaching the policy map to the interface, see the “Attaching the Policy Map to an Interface” section.
To configure network traffic marking, you use the Modular QoS 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, EFP, Trunk EFP, or Xconect by using the service-policy command.
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 a DSCP value of 3 is grouped into another class. The match criteria are 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.
The table below compares the features of traffic classification and traffic marking.
Feature |
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 criteria. |
Uses the traffic classes and matching criteria 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. |
1.
enable
2.
configure
terminal
3.
class-map
class-map-name
[match-all|
match-any]
4.
match cos cos-value
5.
end
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 device.
A policy map
containing the
set
cos command can only be attached as an output
traffic policy.
For Cisco
RSP3 Module, Cos Marking is supported only for pop 0 and push cases. Cos
Marking is
not
supported for pop1 and pop2.
Note
Cos
Marking is not supported for pop 0. Cos marking is supported for pop1 and pop2.
Note
1.
enable
2.
configure
terminal
3.
policy-map
policy-map-name
4.
class
{class-name |
class-default}
5.
set
cos
cos-value
6.
set
dscp
value
7.
end
8.
show
policy-map
9.
show
policy-map
policy-map
class
class-name
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.
Note
Depending on
the needs of your network, policy maps can be attached to targets that are
supported. For information, see
.
3.
service instance
number
ethernet [name]
4.
service-policy
{input |
output}
policy-map-name
5.
encapsulation {default |
dot1q |
priority-tagged |
untagged}
Command or Action | Purpose | |
---|---|---|
Step 1 | configure
terminal
Example: Router# configure terminal | |
Step 2 | interface
interface-id
Example: Router(config)# interface gigabitethernet 0/3/6 |
Specify the port to attach to the policy map, and enter interface configuration mode. Valid interfaces are physical ports. |
Step 3 | service instance
number
ethernet [name]
Example: Rotuer(config)# service instance 1 ethernet |
Configure an EFP (service instance) and enter service instance configuration) mode. |
Step 4 | service-policy
{input |
output}
policy-map-name
Example: Router(config-if-srv)# service-policy input co1 |
Attaches the specified policy map to the input or output interfaces . |
Step 5 | encapsulation {default |
dot1q |
priority-tagged |
untagged}
Example: Router(config-if-srv)# encapsulation dot1q 1 | |
Step 6 | bridge-domain
bridge-id [split-horizon group
group-id]
Example: Router(config-if-srv)# bridge-domain 1 |
Configure the bridge domain ID. The range is from 1 to 4000. You can use the split-horizon keyword to configure the port as a member of a split horizon group. The group-id range is from 0 to 2. |
Step 7 | end
Example: Router(config-if-srv)# end |
Router(config)# interface gigabitethernet 0/3/6 Router(config-if)# service instance 1 ethernet Router(config-if-srv)# service-policy input co1 Router(config-if-srv)# encapsulation dot1q 1 Router(config-if-srv)# bridge-domain 1 Router(config-if-srv)# end
Router> enable Router# configure terminal Router(config)# interface gigabitethernet0/3/6 Router(config-if)# service instance 1 ethernet Router(config-if-srv)# encapsulation dot1q 1 Router(config-if-srv)# bridge-domain 1 Device(config)# class-map match-any class1 Device(config-cmap)# match cos 1 Device(config-cmap)# end
Router> enable Router# configure terminal Router(config)# interface gigabitethernet0/3/6 Router(config-if)# service instance 1 ethernet Router(config-if-srv)# encapsulation dot1q 1 Router(config-if-srv)# bridge-domain 1 Device(config)# class-map match-all class1 Device(config-cmap)# match cos 1 Device(config-cmap)# end
The following is an example of creating a policy map to be used for traffic classification.
Router> enable Router# configure terminal Router(config)# policy-map policy1 Router(config-pmap)# class class1 Router(config-pmap-c)# set cos 2 Router(config-pmap-c)# end Router# exit
The following example shows how to attach an existing traffic policy to an interface. After you define a traffic policy with the policy-map command, you can attach it to one or more interfaces by using the service-policy command in interface configuration mode. Although you can assign the same traffic policy to multiple interfaces, each interface can have only one traffic policy attached in the input direction and only one traffic policy attached in the output direction.
Router(config)# interface gigabitethernet0/3/6 Router(config-if)# service instance 1 ethernet Router(config-if-srv)# service-policy input co1 Router(config-if-srv)# encapsulation dot1q 1 Router(config-if-srv)# bridge-domain 1 Router(config-if)# service-policy input policy1 Router(config-if)# end
Related Topic |
Document Title |
---|---|
Cisco commands |
|
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 |
Classifying network traffic |
“Classifying Network Traffic” module |
Description |
Link |
---|---|
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The following table provides release information about the feature or features described in this module. This table 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.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Feature Name |
Software Releases |
Feature Configuration Information |
---|---|---|
QoS Packet Marking |
Cisco IOS XE Release 3.5S Cisco IOS XE Release 3.16 |
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 to associate a local QoS group value with a packet. In Cisco IOS XE Release 3.5S, support was added for the Cisco ASR 903 Router. In Cisco IOS XE Release 3.16, support was added for the Cisco ASR 900 RSP Module. |