oss Priority Setting
ATM Cell Loss Priority Setting 1
ATM Cell Loss Priority Setting
This feature module describes the ATM Cell Loss Priority (CLP) Setting feature. The ATM CLP
Setting feature allows users to control the CLP bit setting on routers with the PA-A3 port adapter.
This document includes the following sections: Feature Overview, page 1 Supported Platforms, page 2 Supported Standards, MIBs, and RFCs, page 3 Prerequisites, page 3 Conguration Tasks, page 4 Monitoring and Maintaining ATM CLP Setting, page 6 Conguration Example, page 7 Command Reference, page 8 Glossary, page 11
Feature Overview
Before development of the ATM CLP Setting feature, the CLP bit in the ATM header of a cell
provided a method of controlling the discarding of cells in a congested ATM environment. A CLP
bit contains two settings: 0 or 1. Cells with a CLP bit setting of 1 are discarded before cells with a
CLP bit setting of 0. Before the introduction of the ATM CLP Setting feature, the CLP bit was
automatically set to 0 when Cisco routers converted packets into ATM cells for ATM networks.
The ATM CLP Setting feature allows users to control the CLP bit setting on routers with the PA-A3
port adapter. The CLP bit is set on each packet individually, and the default CLP bit setting is 0. The
application of the ATM CLP Setting feature changes the CLP bit setting to 1. Therefore, users have
the option to leave each packet with the default CLP bit setting of 0 or to establish a new CLP bit
setting of 1. Benefits
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Benets
Improved Bandwidth Management
The ATM CLP Setting feature allows users to extend their IP QoS policies into an ATM network by
setting the ATM Cell Loss Priority (CLP) bit in ATM cells based on the IP precedence value of the
packets being transmitted. As congestion occurs in the ATM network, cells with the CLP bit set are
more likely to be dropped, resulting in improved network performance for high priority trafc and
applications.
Restrictions This feature is supported on the PA-A3 port adapter only. A policy map containing the set atm-clp command can be attached as an output policy only. If a policy is attached to a main interface, attaching the same or another policy to the
subinterfaces under the main interface is not permitted. If a policy is attached to a subinterface,
attaching the same or another policy to the main interface is not permitted. Cisco Express Forwarding (CEF) or distributed Cisco Express Forwarding (dCEF) switching is
required. This feature does not support packets that originate from the router.
Related Features and Technologies Quality of Service PA-A3 port adapter Cisco Express Forwarding (CEF) or distributed Cisco Express Forwarding (dCEF)
Related Documents PA-A3 Enhanced ATM Port Adapter Installation and Conguration Guide Quality of Service Networking Cisco Express Forwarding feature module
Supported Platforms Cisco 7200 series Cisco 7500 series Supported Standards, MIBs, and RFCs
ATM Cell Loss Priority Setting 3
Supported Standards, MIBs, and RFCs
Standards No new or modied standards are supported by this feature.
MIBs No new or modied MIBs are supported by this feature.
RFCs No new or modied RFCs are supported by this feature.
Prerequisites
PA-A3
The ATM CLP Setting feature works on the PA-A3 port adapter only.
Class Maps, Policy Maps, and Service Policies
Class maps, policy maps, and service policies are required to enable the ATM CLP Setting feature. Configuration Tasks
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Conguration Tasks
See the following sections for conguration tasks for the ATM CLP Setting feature. Each task in the
list indicates if the task is optional or required. Conguring the ATM CLP Setting Feature (Required) Verifying the ATM CLP Setting Feature (Optional)
Conguring the ATM CLP Setting Feature
You must perform these tasks before you can enable the ATM CLP Setting feature:
Step 1
Dening a Class Map
Step 2
Conguring a Policy with ATM CLP Setting in the Policy Map
Step 3
Attaching the Service Policy and Enabling the ATM CLP Setting Feature
Dening a Class Map
To create a class map containing match criteria, use the class-map command to specify the class map
name, and then use a match command in the class map conguration mode. The Conguring a
Policy with ATM CLP Setting in the Policy Map section below explains how the ATM CLP Setting
feature is applied with this class map.
Command
Purpose
Router(config)#
class-map class-name
Species the user-dened name of class map.
Router(config-cmap)#
match access-group access-group
Species the name of the class map to be created and the
numbered access list against whose contents packets are
checked to determine if they belong to the class.
Router(config-cmap)#
match input-interface interface-name
Species the name of the input interface used as a match
criterion against which packets are checked to determine if
they belong to the class.
Router(config-cmap)#
match protocol protocol
Species the name of the protocol used as a match criterion
against which packets are checked to determine if they belong
to the class.
Router(config-cmap)#
match qos-group number
Species the number of the QoS group index used as a match
criterion against which packets are checked to determine if
they belong to the class.
Router (config-cmap)#
match any
Species that all packets will be matched.
Router (config-cmap)#
match ip precedence number
Species up to eight IP precedence values used as match
criteria.
Router (config-cmap)#
match ip dscp number
Species up to 64 differentiated services code point (DSCP)
values used as match criteria. Verifying the ATM CLP Setting Feature
ATM Cell Loss Priority Setting 5
Conguring a Policy with ATM CLP Setting in the Policy Map
Before enabling the ATM CLP Setting feature, you must create and congure a policy map.
To congure a policy map, use the policy-map command to specify the policy map name, and then
use the following conguration commands to congure the class and the QoS policy. The ATM CLP
Setting feature is congured in the policy map with the set atm-clp command. In this example, all
output packets with the match criteria specied by the class map are sent with the CLP bit set to 1.
If the set atm-clp command was not issued, the default CLP bit setting of 0 would remain.
Attaching the Service Policy and Enabling the ATM CLP Setting Feature
To attach a service policy to an interface, use the service-policy output command in conguration
mode. Once the service-policy is attached to the interface, the ATM CLP Setting feature is enabled
for that interface, provided the set atm-clp command was issued in the policy map conguration,
Verifying the ATM CLP Setting Feature
Step 1
Use the show policy-map command to verify that the ATM CLP Setting feature is
enabled. The set atm-clp line in the output veries that the ATM CLP Setting feature is
congured on the policy map.
Router#
show policy-map
Policy Map Montana
class Joe
set atm-clp
Step 2
Use the show policy-map interface command to verify that the policy map is correctly
congured and attached to the interface:
Router#
show policy-map interface
ATM 10/1/0
service-policy output:x
class-map:a (match-all)
20 packets, 2240 bytes
5 minute rate 0 bps
match:ip precedence 0
Step
Command
Purpose
1
Router(config)#
policy-map policy-name
Species the name of the policy-map to congure.
2
Router(config-pmap)#
class-map class-name
Species the name of a predened class included in the
service policy.
3
Router(config-pmap-c)#
set atm-clp
Congures the ATM CLP Setting feature.
Command
Purpose
Router(config)#
service-policy output policy-name
Enables the Set ATM CLP feature by attaching the
specied policy map to the interface. Monitoring and Maintaining ATM CLP Setting
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Step 3
Use the show atm pvc command to display statistics regarding the PVCs on the interface.
The Out CLP line in the display indicates the cell bit setting. When the ATM CLP
Setting feature is enabled, the Out CLP line is set to 1.
Router#
show atm pvc 120
ATM10/1/0:VCD:120, VPI:0, VCI:120
PeakRate:44209, Average Rate:0, Burst Cells:0
AAL5-LLC/SNAP, etype:0x0, Flags:0xC20, VCmode:0x0
OAM frequency:0 second(s), OAM retry frequency:0 second(s)
OAM up retry count:0, OAM down retry count:0
OAM Loopback status:OAM Disabled
OAM VC state:Not Managed
ILMI VC state:Not Managed
InARP DISABLED
Transmit priority 4
InPkts:0, OutPkts:24, InBytes:0, OutBytes:4608
InPRoc:0, OutPRoc:0, Broadcasts:4
InFast:0, OutFast:0, InAS:0, OutAS:20
InPktDrops:0, OutPktDrops:0
CrcErrors:0, SarTimeOuts:0, OverSizedSDUs:0
Out CLP=1 Pkts:20
OAM cells received:0
F5 InEndloop:0, F5 InSegloop:0, F5 InAIS:0, F5 InRDI:0
F4 InEndloop:0, F4 InSegloop:0, F4 InAIS:0, F4 InRDI:0
OAM cells sent:0
F5 OutEndloop:0, F5 OutSegloop:0, F5 OutRDI:0
F4 OutEndloop:0, F4 OutSegloop:0, F4 OutRDI:0
OAM cell drops:0
Monitoring and Maintaining ATM CLP Setting
To monitor and maintain the ATM CLP Setting feature, use the following commands:
Command
Purpose
Router#
show policy-map
Shows the contents of a policy map.
Router#
show policy-map interface
Shows the contents of a policy map, including the
attached interface.
Router#
show atm pvc
Shows general ATM PVC statistics of the PVCs on the
interface.
Router#
show atm pvc pvc-name
Shows more in-depth ATM PVC statistics of a particular
interface. Configuration Example
ATM Cell Loss Priority Setting 7
Conguration Example
In this example, all output packets with IP precedence values of 0 or 1 are sent with the CLP bit set
to 1:
Router(config)#
class-map Joe
Router(config-cmap)#
match ip precedence 0 1
Router(config-c