QoS: Classification Configuration Guide, Cisco IOS XE Release 3S
Classifying and Marking MPLS EXP
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Contents

Classifying and Marking MPLS EXP

The QoS EXP Matching feature allows you to classify and mark network traffic by modifying the Multiprotocol Label Switching (MPLS) experimental bits (EXP) field in IP packets. This module contains conceptual information and the configuration tasks for classifying and marking network traffic using the MPLS EXP field.

Finding Feature Information

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 at the end of this module.

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.

Prerequisites for Classifying and Marking MPLS EXP

  • The Cisco ASR 903 router must be configured as an MPLS provider edge (PE) or provider (P) router, which can include the configuration of a valid label protocol and underlying IP routing protocols.

Restrictions for Classifying and Marking MPLS EXP

  • MPLS classification and marking can only occur in an operational MPLS Network.
  • MPLS EXP classification and marking is supported on the main router interfaces for MPLS packet switching and imposition (simple IP imposition and Ethernet over MPLS (EoMPLS) imposition) and on Ethernet virtual circuits (EVCs) or Ethernet flow points (EFPs) for EoMPLS imposition.
  • MPLS EXP classification or marking for bridged MPLS packets on EVCs or EFPs is not supported.
  • MPLS EXP marking is supported only in the ingress direction.
  • If a packet is classified by IP type of service (ToS) or class of service (CoS) at ingress, it cannot be reclassified by MPLS EXP at egress (imposition case). However, if a packet is classified by MPLS at ingress it can be reclassified by IP ToS, CoS, or Quality of Service (QoS) group at egress (disposition case).
  • If a packet is encapsulated in MPLS, the MPLS payload cannot be checked for other protocols such as IP for classification or marking. Only MPLS EXP marking affects packets encapsulated by MPLS.

Information About Classifying and Marking MPLS EXP

Classifying and Marking MPLS EXP Overview

The QoS EXP Matching feature allows you to organize network traffic by setting values for the MPLS EXP field in MPLS packets. By choosing different values for the MPLS EXP field, you can mark packets so that packets have the priority that they require during periods of congestion. Setting the MPLS EXP value allows you to:
  • Classify traffic The classification process selects the traffic to be marked. Classification accomplishes this by partitioning traffic into multiple priority levels, or classes of service. Traffic classification is the primary component of class-based QoS provisioning. For more information, see the “Classifying Network Traffic” module.
  • Police and mark traffic Policing causes traffic that exceeds the configured rate to be discarded or marked to a different drop level. Marking traffic is a way to identify packet flows to differentiate them. Packet marking allows you to partition your network into multiple priority levels or classes of service. For more information, see the “Marking Network Traffic” module.

MPLS Experimental Field

The MPLS experimental bits (EXP) field is a 3-bit field in the MPLS header that you can use to define the QoS treatment (per-hop behavior) that a node should give to a packet. In an IP network, the DiffServ Code Point (DSCP) (a 6-bit field) defines a class and drop precedence. The EXP bits can be used to carry some of the information encoded in the IP DSCP and can also be used to encode the dropping precedence.

By default, Cisco IOS Software copies the three most significant bits of the DSCP or the IP precedence of the IP packet to the EXP field in the MPLS header. This action happens when the MPLS header is initially imposed on the IP packet. However, you can also set the EXP field by defining a mapping between the DSCP or IP precedence and the EXP bits. This mapping is configured using the set mpls experimental or police commands. For more information, see the “How to Classify and Mark MPLS EXP” section.

Benefits of MPLS EXP Classification and Marking

If a service provider does not want to modify the value of the IP precedence field in packets transported through the network, they can use the MPLS EXP field value to classify and mark IP packets.

By choosing different values for the MPLS EXP field, you can mark critical packets so that those packets have priority if network congestion occurs.

How to Classify and Mark MPLS EXP

Classifying MPLS Encapsulated Packets


Note

MPLS EXP topmost classification is not supported for bridged MPLS packets on Ethernet virtual circuits (EVC) or Ethernet flow points (EFP).

SUMMARY STEPS

    1.    enable

    2.    configure terminal

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

    4.    match mpls experimental topmost mpls-exp-value

    5.    end


DETAILED STEPS
     Command or ActionPurpose
    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 [match-all | match-any] class-map-name


    Example:
    Router(config)# class-map exp3
     

    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 mpls experimental topmost mpls-exp-value


    Example:
    Router(config-cmap)# match mpls experimental topmost 3
     

    Specifies the match criteria.

    Note   

    The match mpls experimental topmost command classifies traffic on the basis of the EXP value in the topmost label header.

     
    Step 5 end


    Example:
    Router(config-cmap)# end
     

    (Optional) Returns to privileged EXEC mode.

     

    Marking MPLS EXP on All Imposed Labels

    Perform this task to set the value of the MPLS EXP field on all imposed label entries.

    Before You Begin

    The Cisco ASR 903 Router supports MPLS EXP marking only in the ingress direction.

    In typical configurations, marking MPLS packets at imposition is used with ingress classification on IP ToS or CoS fields. However, generic matching with the class default value is supported with other ingress attributes such as vlan.


    Note

    For IP imposition marking, the IP precedence value is copied to the MPLS EXP value by default.


    Note

    For EVC configuration, a policy map that performs matching based on the CoS and that sets the EXP imposition value should be used to copy CoS values to the EXP value.


    Note

    The set mpls experimental imposition command works only on packets that have new or additional MPLS labels added to them.

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    policy-map policy-map-name

      4.    class class-map-name

      5.    set mpls experimental imposition mpls-exp-value

      6.    end


    DETAILED STEPS
       Command or ActionPurpose
      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 mark-up-exp-2
       

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

      • Enter the policy map name.
       
      Step 4 class class-map-name


      Example:
      Router(config-pmap)# class prec012
       

      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 5 set mpls experimental imposition mpls-exp-value


      Example:
      Router(config-pmap-c)# set mpls experimental imposition 2
       

      Sets the value of the MPLS EXP field on all imposed label entries.

       
      Step 6 end


      Example:
      Router(config-pmap-c)# end
       

      (Optional) Returns to privileged EXEC mode.

       

      Marking MPLS EXP on Label Switched Packets

      Perform this task to set the MPLS EXP field on label switched packets.

      Before You Begin

      Note

      The set mpls experimental topmost command works only on packets that are already MPLS encapsulated.


      Note

      The Cisco ASR 903 router supports MPLS EXP marking in the ingress direction only, and does not support MPLS EXP classification or marking for bridged MPLS packets on EVCs or EFPs.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    policy-map policy-map-name

        4.    class class-map-name

        5.    set mpls experimental topmost mpls-exp-value

        6.    end


      DETAILED STEPS
         Command or ActionPurpose
        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 mark-up-exp-2
         

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

        • Enter the policy map name.
         
        Step 4 class class-map-name


        Example:
        Router(config-pmap)# class-map exp012
         

        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 5 set mpls experimental topmost mpls-exp-value


        Example:
        Router(config-pmap-c)# set mpls experimental topmost 2
         

        Sets the MPLS EXP field value in the topmost label on the output interface.

         
        Step 6 end


        Example:
        Router(config-pmap-c)# end
         

        (Optional) Returns to privileged EXEC mode.

         

        Configuring Conditional Marking

        To conditionally set the value of the MPLS EXP field on all imposed label, perform the following task:

        Before You Begin

        Note

        The set-mpls-exp-topmost-transmit action affects MPLS encapsulated packets only. The set-mpls-exp-imposition-transmit action affects any new labels that are added to the packet.


        Note

        The Cisco ASR 903 Router supports conditional marking in the ingress direction only.

        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    policy-map policy-map-name

          4.    class class-map-name

          5.    police cir bps bc pir bps be

          6.    conform-action [set-mpls-exp-imposition-transmit mpls-exp-value | set-mpls-exp-topmost-transmit mpls-exp-value]

          7.    exceed-action [set-mpls-exp-imposition-transmit mpls-exp-value | set-mpls-exp-topmost-transmit mpls-exp-value]

          8.    violate-action drop

          9.    end


        DETAILED STEPS
           Command or ActionPurpose
          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 ip2tag
           

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

          • Enter the policy map name.
           
          Step 4 class class-map-name


          Example:
          Router(config-pmap)# class iptcp
           

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

          • Enter the class map name.
           
          Step 5 police cir bps bc pir bps be


          Example:
          Router(config-pmap-c)# police cir 1000000 pir 2000000
           

          Defines a policer for classified traffic and enters policy-map class police configuration mode.

           
          Step 6 conform-action [set-mpls-exp-imposition-transmit mpls-exp-value | set-mpls-exp-topmost-transmit mpls-exp-value]


          Example:
          Router(config-pmap-c-police)# conform-action set-mpls-exp-imposition-transmit 3
           
          Defines the action to take on packets that conform to the values specified by the policer.
          • In this example, if the packet conforms to the committed information rate (cir) or is within the conform burst (bc) size, the MPLS EXP field is set to 3.
           
          Step 7 exceed-action [set-mpls-exp-imposition-transmit mpls-exp-value | set-mpls-exp-topmost-transmit mpls-exp-value]


          Example:
          Router(config-pmap-c-police)# exceed-action set-mpls-exp-imposition-transmit 2
           

          Defines the action to take on packets that exceed the values specified by the policer.

          • In this example, if the packet exceeds the cir rate and the bc size, but is within the peak burst (be) size, the MPLS EXP field is set to 2.
           
          Step 8 violate-action drop


          Example:
          Router(config-pmap-c-police)# violate-action drop
           
          Defines the action to take on packets whose rate exceeds the peak information rate (pir) and is outside the bc and be ranges.
          • You must specify the exceed action before you specify the violate action.
          • In this example, if the packet rate exceeds the pir rate and is outside the bc and be ranges, the packet is dropped.
           
          Step 9 end


          Example:
          Router(config-pmap-c-police)# end
           

          (Optional) Returns to privileged EXEC mode.

           

          Configuration Examples for Classifying and Marking MPLS EXP

          Example: Classifying MPLS Encapsulated Packets

          Defining an MPLS EXP Class Map

          The following example defines a class map named exp3 that matches packets that contains MPLS experimental value 3: 

          Router(config)# class-map exp3 
Router(config-cmap)# match mpls experimental topmost 3 
Router(config-cmap)# exit

          Defining a Policy Map and Applying the Policy Map to an Ingress Interface

          The following example uses the class map created in the example above to define a policy map. This example also applies the policy map to a physical interface for ingress traffic. 

          Router(config)# policy-map change-exp-3-to-2
Router(config-pmap)# class exp3
Router(config-pmap-c)# set mpls experimental topmost 2
Router(config-pmap)# exit
Router(config)# interface GigabitEthernet 0/0/0
Router(config-if)# service-policy input change-exp-3-to-2
Router(config-if)# exit

          Defining a Policy Map and Applying the Policy Map to an Egress Interface

          The following example uses the class map created in the example above to define a policy map. This example also applies the policy map to a physical interface for egress traffic. 

          Router(config)# policy-map WAN-out
Router(config-pmap)# class exp3
Router(config-pmap-c)# shape average 10000000
Router(config-pmap-c)# exit
Router(config-pmap)# exit
Router(config)# interface GigabitEthernet 0/0/0
Router(config-if)# service-policy output WAN-out
Router(config-if)# exit

          Example: Marking MPLS EXP on All Imposed Labels

          Defining an MPLS EXP Imposition Policy Map

          The following example defines a policy map that sets the MPLS EXP imposition value to 2 based on the IP precedence value of the forwarded packet: 

          Router# configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)# class-map prec012
Router(config-cmap)# match ip prec 0 1 2
Router(config-cmap)# exit
Router(config)# policy-map mark-up-exp-2
Router(config-pmap)# class prec012
Router(config-pmap-c)# set mpls experimental imposition 2
Router(config-pmap-c)# exit
Router(config-pmap)# exit

          Applying the MPLS EXP Imposition Policy Map to a Main Interface

          The following example applies a policy map to Gigabit Ethernet interface 0/0/0: 

          Router# configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)# interface GigabitEthernet 0/0/0
Router(config-if)# service-policy input mark-up-exp-2
Router(config-if)# exit

          Applying the MPLS EXP Imposition Policy Map to an EVC

          The following example applies a policy map to the Ethernet Virtual Connection sepecified by the service instance command: 

          Router# configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)# interface GigabitEthernet 0/0/0
Router(config-inf)# service instance 100 ethernet
Router(config-if-srv)# xconnect 100.0.0.1 encapsulation mpls 100
Router(config-if-srv)# service-policy input mark-up-exp-2
Router(config-if-srv)# exit
Router(config-if)# exit

          Example: Marking MPLS EXP on Label Switched Packets

          Defining an MPLS EXP Label Switched Packets Policy Map

          The following example defines a policy map that sets the MPLS EXP topmost value to 2 according to the MPLS EXP value of the forwarded packet: 

          Router# configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)# class-map exp012
Router(config-cmap)# match mpls experimental topmost 0 1 2
Router(config-cmap)# exit
Router(config-cmap)# policy-map mark-up-exp-2
Router(config-pmap)# class exp012
Router(config-pmap-c)# set mpls experimental topmost 2
Router(config-pmap-c)# exit
Router(config-pmap)# exit

          Applying the MPLS EXP Label Switched Packets Policy Map to a Main Interface

          The following example shows how to apply the policy map to a main interface: 

          Router# configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)# interface GigabitEthernet 0/0/0
Router(config-if)# service-policy input mark-up-exp-2
Router(config-if)# exit

          Example: Configuring Conditional Marking

          The example in this section creates a policer for the iptcp class, which is part of the ip2tag policy map, and attaches the policy map to the Gigabit Ethernet interface. 

          Router(config)# policy-map ip2tag
Router(config-pmap)# class iptcp
Router(config-pmap-c)# police cir 1000000 pir 2000000
Router(config-pmap-c-police)# conform-action set-mpls-exp-imposition-transmit 3
Router(config-pmap-c-police)# exceed-action set-mpls-exp-imposition-transmit 2
Router(config-pmap-c-police)# violate-action drop
Router(config-pmap-c-police)# exit
Router(config-pmap-c)# exit
Router(config-pmap)# exit
Router(config)# interface GigabitEthernet 0/0/1
Router(config-if)# service-policy input ip2tag

          Additional References

          Related Documents

          Related Topic

          Document Title

          Cisco IOS commands

          Cisco IOS Master Commands List, All Releases

          QoS commands

          Cisco IOS Quality of Service Solutions Command Reference

          Classifying network traffic

          “Classifying Network Traffic” module

          Marking network traffic

          “Marking Network Traffic” module

          Standards and RFCs

          Standard/RFC

          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 software releases, and feature sets, use Cisco MIB Locator found at the following URL:

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

          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 Classifying and Marking MPLS EXP

          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.

          Table 1 Feature Information for Classifying and Marking MPLS EXP

          Feature Name

          Releases

          Feature Information

          QoS EXP Matching

          Cisco IOS XE Release 3.5S

          QoS EXP matching allows you to classify and mark packets using the MPLS EXP field.

          In Cisco IOS XE Release 3.5S, this feature was introduced on the Cisco ASR 903 Router.