Asynchronous Transfer Mode Configuration Guide, Cisco IOS XE Release 3S
N:1 PVC Mapping to PWE with Nonunique VPIs
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N:1 PVC Mapping to PWE with Nonunique VPIs

Last Updated: August 8, 2012

The N:1 PVC Mapping to PseudoWire Emulation (PWE) with Nonunique virtual path identifiers (VPIs) feature maps one or more ATM permanent virtual circuits (PVCs) to a single pseudowire (PW). There are two modes of AAL0 encapsulation, N:1 and 1:1 mapping. In N:1 mapping, multiple unrelated virtual path identifier/virtual channel identifier (VPI/VCI) are carried over a single Multiprotocol Label Switching (MPLS) PW. This is an efficient mapping method because less resources are used from the MPLS network. In 1:1 mapping, a single VPI/VCI is carried over a single MPLS PW. Benefits of this feature include the following:

  • Aggregate quality of service (QoS) can be applied to related PVCs.
  • Bandwidth is conserved with the reduction in the number of pseudowires that are used.

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.

Restrictions for N:1 PVC Mapping to PWE with Nonunique VPIs

  • N:1 permanent virtual circuits (PVC) mapping configuration is supported only on multipoint subinterfaces; it is not supported on main interfaces or point-to-point subinterfaces.
  • N:1 PVC mapping mode is not supported on Access Circuit Redundancy subinterfaces.
  • Preconfigured PVCs cannot exist on the multipoint subinterface on which you want to configure N:1 PVC mapping.
  • An attachment circuit that has been bound to a pseudowire cannot be removed unless all Layer 2 virtual circuits (VCs) have been removed.
  • Layer 3 PVCs cannot be configured on N:1 subinterfaces.
  • Cell packing values configured under a VC class attached to the PVC, main interface, or subinterface will not be inherited by N:1 PVCs.
  • Operation, Administration, and Maintenance (OAM) functionality is not supported on N:1 Layer 2 PVCs. OAM cells coming from the customer edge (CE) network will be treated as normal data traffic and will traverse through the pseudowire.
  • Only ATM adaptation layer type 0 (AAL0) encapsulation is supported for N:1 PVCs.
  • The service policy configuration can be configured only at the subinterface level for N:1 PVCs.

Information About N:1 PVC Mapping to PWE with Nonunique VPIs

N:1 PVC Mapping to PWE with Nonunique VPIs Feature Description

To transport ATM cells over Multiprotocol Label Switching (MPLS), a VC is established between the provider edge (PE) routers on both ends of the MPLS backbone. With the N:1 permanent virtual circuit (PVC) Mapping to PseudoWire Emulation (PWE) with Nonunique VPIs feature, multiple PVCs irrespective of their Virtual Path Identifiers (VPIs), are transported over a single pseudowire configured on a subinterface. ("N:1" refers to the number of PVCs transported over one pseudowire). ATM cells are packed together in a single frame and sent over the single pseudowire. The ATM cell header information is packed together with the cell payload on a per-cell basis in the packets so that packets received at the egress end are unpacked and the ATM cells are mapped to the respective PVCs.

In N:1 PVC mapping mode, the device can pack cells only from a single PVC in an MPLS packet to transmit over a pseudowire; cells from multiple PVCs cannot be packed in a single MPLS packet and mapped to a single pseudowire for transmission. However, if a device receives an MPLS packet that is packed with cells from multiple PVCs, then those cells will be unpacked and sent to the respective PVCs.

How to Configure N:1 PVC Mapping to PWE with Nonunique VPIs

Configuring N:1 PVC Mapping to PWE with Nonunique VPIs

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface atm slot/subslot/port

4.    atm mcpt-timers timer1 timer2 timer3

5.    exit

6.    configure terminal

7.    interface atm slot/subslot/portt.subslot multipoint

8.    no ip address

9.    atm enable-ilmi-trap

10.    cell-packing maxcells mcpt-timer timer-number

11.    xconnect peer-ipaddress vc-id encapsulation mpls

12.    pvc vpi/vci l2transport

13.    Repeat Step 12 for the number of PVCs that you want to configure.

14.    end


DETAILED STEPS
 Command or ActionPurpose
Step 1
enable


Example:

Device> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Device# configure terminal

 

Enters global configuration mode.

 
Step 3
interface atm slot/subslot/port


Example:

Device(config)# interface atm 9/1/1

 

Enables the ATM interface and enters interface configuration mode.

 
Step 4
atm mcpt-timers timer1 timer2 timer3


Example:

Device(config-if)# atm mcpt-timers 100 200 300

 

Sets the Maximum Cell Packing Timeout (MCPT) values in microseconds.

  • The MCPT timer sets the time for which the device waits for the raw cells (AAL0 encapsulation) to be packed into a single packet for punting to the pseudowire.
 
Step 5
exit


Example:

Device(config-if)# exit

 

Exits interface configuration mode.

 
Step 6
configure terminal


Example:

Device# configure terminal

 

Enters global configuration mode.

 
Step 7
interface atm slot/subslot/portt.subslot multipoint


Example:

Device(config)# interface atm 9/1/1.1 multipoint

 

Enters subinterface configuration mode and creates a multipoint subinterface on the given port on the specified ATM Shared Port Adapter (SPA).

 
Step 8
no ip address


Example:

Device(config-subif)# no ip address

 

Removes the interface IP address.

 
Step 9
atm enable-ilmi-trap


Example:

Device(config-subif)# atm enable-ilmi-trap

 

Generates an Integrated Local Management Interface (ILMI) atmfVccChange trap when an ATM interface or subinterface is enabled or shut down.

 
Step 10
cell-packing maxcells mcpt-timer timer-number


Example:

Device(config-subif)# cell-packing 20 mcpt-timer 2

 

Enables ATM over MPLS to pack multiple ATM cells into each MPLS packet within the MCPT timing.

 
Step 11
xconnect peer-ipaddress vc-id encapsulation mpls


Example:

Device(config-subif)# xconnect 10.1.1.1 100 encapsulation mpls

 

(Optional) Enables the attachment circuit and specifies the IP address of the peer, a VC ID, and the data encapsulation method.

 
Step 12
pvc vpi/vci l2transport


Example:

Device(config-subif)# pvc 10/100 l2transport

 

Assigns a VPI and virtual channel identifier (VCI).

 
Step 13
Repeat Step 12 for the number of PVCs that you want to configure.  

--

 
Step 14
end


Example:

Device(config-subif)# end

 

Exits subinterface configuration mode and returns to privileged EXEC mode.

 

Configuration Examples for N:1 PVC Mapping to PWE with Nonunique VPIs

Example: Configuring N:1 PVC Mapping to PWE with Nonunique VPIs

The following example shows how to configure the N:1 ATM permanent virtual circuit (PVC) mapping to pseudowires with non unique virtual path identifiers ( VPIs): 

Device> enable
Device# configure terminal
Device(config)# interface atm 9/1/1
Device(config-if)# atm mcpt-timers 500 5000 50000
Device(config-if)# exit
Device# configure terminal
Device(config)# interface atm 9/1/1.1 multipoint
Device(config-subif)# no ip address
Device(config-subif)# atm enable-ilmi-trap
Device(config-subif)# cell packing 20 mcpt-timer 2
Device(config-subif)# xconnect 10.1.1.1 100 encapsulation mpls
Device(config-subif)# pvc 10/100 l2transport
Device(config-subif)# pvc 11/122 l2transport
Device(config-subif)# pvc 19/231 l2transport
Device(config-subif)# end

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Master Command List

ATM commands

Asynchronous Transfer Mode Command Reference

Technical Assistance

Description

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

Feature Information for N:1 PVC Mapping to PWE with Nonunique VPIs

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 1Feature Information for N:1 PVC Mapping to PWE with Nonunique VPIs
Feature Name Releases Feature Information
N:1 PVC Mapping to PWE with Nonunique VPIs Cisco IOS XE Release 3.7S

The N:1 PVC Mapping to PWE with Nonunique VPIs feature maps one or more ATM PVCs to a single pseudowire. In Cisco IOS XE Release 3.7S, support was added for Cisco ASR 903 Routers.

The following command was introduced by this feature: show atm cell-packaging .

© 2012 Cisco Systems, Inc. All rights reserved.