Usage Guidelines

Within a policy map, the class (policy-map) command can be used to specify the name of the class whose policy you want to create or change. The policy map must be identified first.

To identify the policy map (and enter the required policy map configuration mode), use the policy-map command before you use the class (policy-map) command. After you specify a policy map, you can configure the policy for new classes or modify the policy for any existing classes in that policy map.

The class name that you specify in the policy map ties the characteristics for that class—that is, its policy—to the class map and its match criteria, as configured using the class-map command.

RP/0/RP0/CPU0:router(config)# class-map p2
RP/0/RP0/CPU0:router(config-cmap)# match precedence 2
RP/0/RP0/CPU0:router(config-cmap)# end-class-map
RP/0/RP0/CPU0:router(config)# commit

RP/0/RP0/CPU0:router(config)# policy-map pm2 
RP/0/RP0/CPU0:router(config-pmap)# class p2 
RP/0/RP0/CPU0:router(config-pmap-c)# set precedence 3 
RP/0/RP0/CPU0:router(config-pmap-c)# end-policy-map 
RP/0/RP0/CPU0:router(config)# commit 
RP/0/RP0/CPU0:router(config)# end 


RP/0/RP0/CPU0:router# show run policy-map pm2 
policy-map pm2
class p2
set precedence 3
! 
class class-default
! 
end-policy-map
!
  

Usage Guidelines

The class-map command specifies the name of the class for which you want to create or modify class map match criteria. Use of this command enables class map configuration mode in which you can enter any match command to configure the match criteria for this class. Packets arriving on the interface are checked against the match criteria configured for a class map to determine if the packet belongs to that class.

These commands can be used in a class map match criteria for the ingress direction:

• match access-group
• match [not] dscp
• match [not] mpls experimental topmost
• match [not] precedence
• match [not] protocol

Usage Guidelines

No specific guidelines impact the use of this command.

Usage Guidelines

No specific guidelines impact the use of this command.

Usage Guidelines

The router must be reloaded for the hw-module command to be functional.

Usage Guidelines

The router must be reloaded for the hw-module command to be functional.

This command only applies to ingress policies and only 4, 8, 16, or 32 classes per policy-map are supported. Egress policies can support up to 8 classes per policy-map.

Usage Guidelines

The router must be reloaded for the hw-module command to be functional.

Usage Guidelines

For class-based features (such as marking and policing), you define traffic classes based on match criteria, including ACLs and input interfaces. Packets satisfying the match criteria for a class constitute the traffic for that class.

The match access-group command specifies an ACL whose contents are used as the match criteria against which packets are checked to determine if they belong to the class specified by the class map.

The match access-group command is supported only in the ingress direction. The maximum allowed entries: 8

To use the match access-group command, you must first enter the class-map command to specify the name of the class whose match criteria you want to establish. You can specify up to eight IPv4 and IPv6 ACLs in a match statement.

QoS classification based on the packet length or TTL (time to live) field in the IPv4 and IPv6 headers is not supported.

When an ACL list is used within a class-map, the deny action of the ACL is ignored and the traffic is classified based on the specified ACL match parameters.

Usage Guidelines

The match cos command is supported only in the ingress direction.

The match cos command specifies a class of service that is used as the match criteria against which packets are checked to determine if they belong to the class specified by the class map.

To use the match cos command, you must first enter the class-map command to specify the name of the class whose match criteria you want to establish. If you specify more than one match cos command in a class map, the values of subsequent match statements are added to the first match cos command.

Usage Guidelines

The match dei command specifies a DEI value that is used as the match criteria against which packets are checked to determine if they belong to the class specified by the class map.

Usage Guidelines

The match dscp command is supported only in the ingress direction. The minimum value is 0 and maximum value is 63. The maximum allowed entries: 64.

The match dscp command specifies a DSCP value that is used as the match criteria against which packets are checked to determine if they belong to the class specified by the class map.

To use the match dscp command, you must first enter the class-map command to specify the name of the class whose match criteria you want to establish

The match dscp command examines the higher-order six bits in the type of service (ToS) byte of the IP header. If you specify more than one match dscp command in a class map, the new values are added to the existing statement.

The IP DSCP value is used as a matching criterion only. The value has no mathematical significance. For instance, the IP DSCP value 2 is not greater than 1. The value simply indicates that a packet marked with the IP DSCP value of 2 should be treated differently than a packet marked with an IP DSCP value of 1. The treatment of these marked packets is defined by the user through the setting of policies in policy map class configuration mode.

Usage Guidelines

The match mpls disposition class-map <cmap-name> command is supported only in the ingress direction. It contains the child class-map name as argument which can have match dscp <value> or match precedence <value> statements. The minimum value for DSCP is 0 and the maximum value is 63. The maximum allowed entries are 8.

The class map uses this command to identify DSCP and/or precedence values matching on a packet.

To use this command, you must first enter the class-map command to specify the name of the class whose match criteria you want to establish. If you specify more than one match mpls disposition class-map <cmap-name> command in a class map, the new values are added to the existing match statement.

This command examines the DSCP/precedence bits contained in the IPv4/IPv6 header.

Usage Guidelines

The match mpls experimental topmost command is supported only in the ingress direction. The minimum value is 0 and maximum value is 7. The maximum allowed entries: 8.

The match mpls experimental topmost command is used by the class map to identify MPLS experimental values matching on a packet.

To use the match mpls experimental topmost command, you must first enter the class-map command to specify the name of the class whose match criteria you want to establish. If you specify more than one match mpls experimental topmost command in a class map, the new values are added to the existing match statement.

This command examines the three experimental bits contained in the topmost label of an MPLS packet. Up to eight experimental values can be matched in one match statement. For example, match mpls experimental topmost 2 4 5 7 returns matches for experimental values of 2, 4, 5, and 7. Only one of the four values is needed to yield a match (OR operation).

The experimental values are used as a matching criterion only. The value has no mathematical significance. For instance, the experimental value 2 is not greater than 1. The value indicates that a packet marked with the experimental value of 2 should be treated differently than a packet marked with the EXP value of 1. The treatment of these different packets is defined by the user through the setting of QoS policies in policy map class configuration mode.

Usage Guidelines

The match precedence command is supported only in the ingress direction. The minimum value is 0 and maximum value is 7. The maximum allowed entries: 8.

The match precedence command specifies a precedence value that is used as the match criteria against which packets are checked to determine if they belong to the class specified by the class map.

To use the match precedence command, you must first enter the class-map command to specify the name of the class whose match criteria you want to establish. If you specify more than one match precedence command in a class map, the new values are added to the existing statement.

The match precedence command examines the higher-order three bits in the type of service (ToS) byte of the IP header. Up to eight precedence values can be matched in one match statement. For example, match precedence ipv4 0 1 2 3 4 5 6 7 returns matches for IP precedence values of 0, 1, 2, 3, 4, 5, 6, and 7. Only one of the eight values is needed to yield a match (OR operation).

The precedence values are used as a matching criterion only. The value has no mathematical significance. For instance, the precedence value 2 is not greater than 1. The value simply indicates that a packet marked with the precedence value of 2 is different than a packet marked with the precedence value of 1. The treatment of these different packets is defined by the user through the setting of QoS policies in policy map class configuration mode.

This table lists the IP precedence value number and associated name in descending order of importance.

Usage Guidelines

The match protocol command is supported only in ingress direction. The maximum allowed entry is 1.

Definitions of traffic classes are based on match criteria, including protocols, access control lists (ACLs), input interfaces, QoS labels, and experimental (EXP) field values. Packets satisfying the match criteria for a class constitute the traffic for that class.

The match protocol command specifies the name of a protocol to be used as the match criteria against which packets are checked to determine if they belong to the class specified by the class map. Available protocol names are listed in the table that follows.

The protocol-value argument supports a range of protocol numbers. After you identify the class, you may use the match protocol command to configure its match criteria.

Usage Guidelines

The match qos-group command is supported only in the egress direction. The egress default class will implicitly match qos-group 0. The minimum value is 1 and maximum value is 7. The maximum allowed entries: 7.

The match qos-group command sets the match criteria for examining QoS groups marked on the packet. One class map can match only one qos-group value from 1 to 7. The qos-group values 1 to 7 maps to queue 1 to 7 on the egress port. Queue 0 is reserved for class-default.

The QoS group value is used as a matching criterion only. The value has no mathematical significance. For instance, the QoS group value 2 is not greater than 1. The value simply indicates that a packet marked with the QoS group value of 2 should be treated differently than a packet marked with a QoS group value of 1. The treatment of these different packets is defined using the service-policy command in policy map class configuration mode.

The QoS group setting is limited in scope to the local router. Typically, the QoS group is set on the ingress on the local router to be used locally and the router to give differing levels of service based on the group identifier.

In the ingress policy-map, in order to designate the traffic class to a certain CoSQ other than CoSQ 0, the class-map needs to have an explicit set qos-group x statement, where 'x' is the CoSQ in the range of 0 to 7. The default COSQ is 0. In the egress policy-map, a class-map with a corresponding match qos-group x will allow further Quality of Service actions to be applied to the traffic class. For example,

class-map prec1
  match prec 1
 
policy-map test-ingress
  class prec1
    set qos-group 1
    police rate percent 50
 
 
class-map qg1
  match qos-group 1
 
 
policy-map test-egress
  class qg1
    shape average percent 70

Usage Guidelines

WRED is a congestion avoidance mechanism that slows traffic by randomly dropping packets when congestion exists. WRED is most useful with protocols like TCP that respond to dropped packets by decreasing the transmission rate.

When you configure the random-detect discard-class command on an interface, packets are given preferential treatment based on the discard class of the packet.

When the value of the units argument is packets, packets are assumed to be 256 bytes in size.

Usage Guidelines

Use the set cos command to mark a packet that is being sent to a switch. Switches can leverage Layer 2 header information, including a CoS value marking.

The set cos command is supported only in the ingress direction. Only unconditional COS marking in the ingress direction is supported.

Usage Guidelines

The set dei command specifies a DEI value in a policy map class. For example, traffic can be policed and the excess traffic can be marked with DEI value of 1, so that it can be preferentially dropped in the egress interface or further downstream, when there is congestion.

Usage Guidelines

The set discard-class command associates a discard class ID with a packet. After the discard class is set, other QoS services such as Weighted Random Early Detection (WRED) can operate on the bit settings.

Discard-class indicates the discard portion of the per hop behavior (PHB). The set discard-class command is typically used in Pipe mode. Discard-class is required when the input PHB marking is used to classify packets on the output interface.

The set discard-class command is supported only in the ingress direction. Unconditional discard-class marking is supported.

The discard-class values can be used to specify the type of traffic that is dropped when there is congestion.

Note	Marking of the discard class has only local significance on a node. Discard class cannot be associated with a QoS profile in peering mode.

Usage Guidelines

After the DSCP bit is set, other quality-of-service (QoS) services can then operate on the bit settings. The set dscp is supported only in the ingress direction.

The network gives priority (or some type of expedited handling) to marked traffic. Typically, you set the DSCP value at the edge of the network (or administrative domain); data then is queued based on the DSCP value.

Usage Guidelines

After the MPLS experimental bits are set, other QoS services can then operate on the bit settings.

This command is supported only in ingress direction. Unconditional MPLS experimental marking is supported.

The network gives priority (or some type of expedited handling) to the marked traffic. Typically, the MPLS experimental value is set at the edge of the network (or administrative domain) and queuing is acted on it thereafter.

Usage Guidelines

Precedence can be set using a number or corresponding name. After IP Precedence bits are set, other QoS services can then operate on the bit settings.

The set precedence command is supported only in the ingress direction. Unconditional precedence marking is supported.

The network gives priority (or some type of expedited handling) to the marked traffic. IP precedence can be set at the edge of the network (or administrative domain) and have queueing act on it thereafter.

The mapping from keywords such as 0 (routine) and 1 (priority) to a precedence value is useful only in some instances. That is, the use of the precedence bit is evolving. You can define the meaning of a precedence value by enabling other features that use the value. In the case of high-end Internet QoS, IP precedences can be used to establish classes of service that do not necessarily correspond numerically to better or worse handling in the network.

Usage Guidelines

The set qos-group command is supported only in the ingress direction.

The set qos-group will be used as internal priority to choose the queue on the egress port.

In the ingress policy-map, in order to designate the traffic class to a certain CoSQ other than CoSQ 0, the class-map needs to have an explicit set qos-group x statement, where 'x' is the CoSQ in the range of 0 to 7. The default COSQ is 0. In the egress policy-map, a class-map with a corresponding match qos-group x will allow further Quality of Service actions to be applied to the traffic class. For example,

class-map prec1
  match prec 1
 
policy-map test-ingress
  class prec1
    set qos-group 1
    police rate percent 50
 
 
class-map qg1
  match qos-group 1
 
 
policy-map test-egress
  class qg1
    shape average percent 70

Usage Guidelines

The shape average command is supported only in the egress direction.

When you use the shape average command, egress shaping is done at the Layer 1 level and includes the Layer 1 header in the rate calculation. The minimum shape rate is 469 kbps. If you have both shape and bandwidth configured for a class, ensure that the shape percent value is always greater than the percent value for bandwidth. For bundled interfaces, shape average can be configured only as a percentage.

The priority and shape average commands can be configured together in the same class.