PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

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Updated:December 20, 2007

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PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

Table Of Contents

PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

Finding Feature Information

Contents

Prerequisites for the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

Information About the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

Differences Between ATM- and Ethernet-Based Broadband Access Networks

DSL Forum 2004-71: Solution for Remote-ID in PPPoE Discovery Phase

Remote-ID Tag in Ethernet-Based Broadband Access Networks

Benefits of the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

How to Configure the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

Configuring the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement Feature

Stripping Vendor-Specific Tags

Troubleshooting Tips

Configuration Examples for the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

Configuring PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement: Example

Stripping Vendor-Specific Tags: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

Glossary


PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

First Published: December 4, 2006
Last Updated: October 2, 2009

The PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement feature provides a method by which the digital subscriber line access multiplexer (DSLAM) sends the DSL Remote-ID tag in the discovery phase as an identifier for the authentication, authorization, and accounting (AAA) access request on an Ethernet interface, thereby simulating ATM-based broadband access, but using cost-effective Ethernet instead. This Remote-ID tag is useful for troubleshooting, authentication, and accounting.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see 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 for PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

•Information About the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

•How to Configure the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

•Configuration Examples for the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

•Additional References

•Feature Information for PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

•Glossary

Prerequisites for the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

It is recommended that you be familiar with the following documents before configuring this feature:

•RFC 2516: A Method for Transmitting PPP over Ethernet (PPPoE)

•DSL Forum 2004-71: Solution for Remote-ID in PPPoE Discovery Phase

See the "Additional References" section for more information.

Information About the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

To configure the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement feature, you should understand the following concepts:

•Differences Between ATM- and Ethernet-Based Broadband Access Networks

•DSL Forum 2004-71: Solution for Remote-ID in PPPoE Discovery Phase

•Remote-ID Tag in Ethernet-Based Broadband Access Networks

•Benefits of the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

Differences Between ATM- and Ethernet-Based Broadband Access Networks

Broadband DSLAM and Broadband Remote Access Server (BRAS) vendors need to provide Ethernet-based networks as an alternative to an ATM access network, with a DSLAM bridging the ATM-DSL local loop to the Ethernet-based broadband access network and allowing Ethernet-based connectivity to the BRAS. There is no unique mapping between the subscriber Line-ID tag and the interface in an Ethernet broadband access network, as there is in an ATM-based broadband network, where the ATM VC is associated to a subscriber line. During the authentication phase that initiates the PPP access and AAA accounting requests, the BRAS includes a NAS-Port-ID attribute in RADIUS authentication packets that identifies the DSL for the subscriber.

DSL Forum 2004-71: Solution for Remote-ID in PPPoE Discovery Phase

DSL Forum 2004-71 defines a method whereby the DSLAM sends the DSL Remote-ID tag in the PPP over Ethernet (PPPoE) discovery phase to apply the same subscriber mapping capability to Ethernet interfaces that is possible on ATM interfaces. This method adds support for the PPPoE server acting as a BRAS to report the Remote-ID tag as a new vendor specific attribute (VSA) (AAA_AT_REMOTE_ID) in AAA authentication and accounting requests. If the radius-server attribute 31 remote-id command is configured on the BRAS, the Remote-ID tag will be sent to a RADIUS server as the Calling Station-ID tag (attribute 31).

Remote-ID Tag in Ethernet-Based Broadband Access Networks

Traditional ATM-based DSL broadband access networks have the topology shown in Figure 1.

Figure 1 ATM-Based DSL Broadband Access Network

In terms of logical connectivity, there is a one-to-one mapping of the DSL subscriber line to the end user and the ATM virtual circuit (VC) used to carry the PPP session through the DSLAM and to the BRAS, where this VC information is converted into a NAS-Port-ID tag for use in RADIUS packets.

The simple mapping available from an ATM-based broadband network between the physical line in the DSL local loop to the end user and a virtual circuit (from DSLAM to BRAS) is not available for an Ethernet-based network. To solve this problem, the PPPoE Remote-ID Tag Processing feature uses a PPPoE intermediate agent function on the DSLAM to attach a tag to the PPPoE discovery packets. The BRAS then receives the tagged packet, decodes the tag, and inserts the line identifier into RADIUS packets destined for the RADIUS server.

The DSLAM intercepts PPPoE discovery frames from the client or initiates a discovery frame if the PPPoE Active Discovery (PAD) client is a legacy PPP over ATM (PPPoA) device. The DSLAM inserts a unique Remote-ID tag and DSL sync rate tag using the PPPoE vendor-specific tag (0x0105) to PPPoE Active Discovery Initiation (PADI) and PPPoE Active Discovery Request (PADR) packets; see Figure 2. The DSLAM forwards these packets upstream to the BRAS after the insertion. The tag contains the identification of the DSL line on which the PADI or PADR packet was received, in the access node where the intermediate agent resides.

Figure 2 PPPoE Remote-ID Tag Processing Solution

When the vendor-tag remote-id service command is configured in broadband access (BBA) group configuration mode, the BRAS processes the received PPPoE vendor-specific tag in the PADR frame and extracts the Remote-ID tag, which is sent to the remote AAA server as a VSA in all AAA access and accounting requests. When the radius-server attribute 31 remote-id global configuration command is also configured on the BRAS, the Remote-ID value is inserted into attribute 31.

Outgoing PAD Offer (PADO) and PAD Session-Confirmation (PADS) packets from the BRAS have the DSLAM-inserted Remote-ID tag. The DSLAM should strip the tag out of PADO and PADS frames. If the DSLAM cannot strip off the tag, the BRAS must remove the tag before sending the frames out. This is accomplished using the vendor-tag strip BBA group configuration mode command. If this command is configured under the BBA group, the BRAS strips the incoming Remote-ID tag (and any other vendor tag) off of the outgoing PADO and PADS frames. This action complies with DSL Forum Technical Report 101.

Benefits of the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

The shift toward Ethernet-based DSLAMs offers the following benefits:

•Ability to use simpler and lower-cost provisioning options for DSL subscribers over an Ethernet-based backhaul network rather than on an ATM-based network.

•Ability to use higher bandwidth connectivity options available from Ethernet that are not possible on ATM.

•Ability to upgrade to next-generation DSLAMs with quality of service (QoS), and support for higher bandwidth, asymmetric dual latency modems such as the ADSL2.

•Ability to inject high-bandwidth content such as video in an Ethernet network.

How to Configure the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

This section contains the following procedures:

•Configuring the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement Feature

•Stripping Vendor-Specific Tags

Configuring the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement Feature

This task describes how to configure the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement feature. When this feature is configured, BRAS will process the incoming PADR frames and send the Remote-ID field of the incoming tag to the RADIUS server as a VSA.

For DSL-Sync-Rate tags, you must enter the vendor-tag dsl-sync-rate service command under a BBA group. When this command is entered, the BRAS will process incoming PADR frames and send the DSL-Sync-Rate tags to the RADIUS server as VSAs.

An Access-Accept message is sent by the RADIUS server and vendor-tag attributes sent in the Access-Request message will be present in the Access-Accept message if the RADIUS server echoes it back.

SUMMARY STEPS

1. enable

2. configure terminal

3. aaa new-model

4. radius-server attribute 31 remote-id

5. bba-group pppoe {group-name | global}

6. vendor-tag remote-id service

7. vendor-tag dsl-sync-rate service

8. nas-port-id format c

DETAILED STEPS

 
Command or Action
Purpose

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 

aaa new-model

Example:

Router(config)# aaa new-model

(Optional) Enables the AAA access control model.

Step 4 

radius-server attribute 31 remote-id

Example:

Router(config)# radius-server attribute 31 remote-id

(Optional) Sends the Remote-ID tag to the RADIUS server via a new VSA (AAA_AT_REMOTE_ID) and in attribute 31—Calling Station ID.

•Configure this command so that the Acct-Session-ID attribute, as displayed in the debug radius command, will contain the information about the incoming access interface, where discovery frames are received, and about the session being established. See the "Troubleshooting Tips" section that follows the "Stripping Vendor-Specific Tags" task.

Step 5 

bba-group pppoe {group-name | global}

Example:

Router(config)# bba-group pppoe pppoe-group

Defines a PPPoE profile and enters BBA group configuration mode.

Step 6 

vendor-tag remote-id service

Example:

Router(config-bba-group)# vendor-tag remote-id service

Enables the BRAS to process incoming PADR frames and send the Remote-ID field of the incoming tag to the RADIUS server as a VSA.

Step 7 

vendor-tag dsl-sync-rate service

Example:

Router(config-bba-group)# vendor-tag dsl-sync-rate service

Enables the BRAS to process the incoming PADR frames and send the DSL-Sync-Rate tags to the RADIUS server as VSAs.

Step 8 

nas-port-id format c

Example:

Router(config-bba-group)# nas-port-id format c

Specifies a format for broadband subscriber access line identification coding.

•The designation of format c is specifically designed for a particular coding format. A sample of this format is as follows:

NAS_PORT_ID=atm 31/31/7:255.65535 example001/0/31/63/31/127

•This means the subscriber interface type of the BRAS equipment is an ATM interface. The BRAS slot number is 31, and the BRAS subslot number is 31. The BRAS port number is 7. The virtual path identifier (VPI) is 255, and the virtual circuit identifier (VCI) is 65535.

The Circuit-ID/Remote-ID tag is example001/0/31/63/31/127.

Stripping Vendor-Specific Tags

Outgoing PADO and PADS packets will have the DSLAM-inserted Remote-ID and DSL-Sync-Rate tags, and the DSLAM must strip these tags from the packets. If the DSLAM cannot strip the tag, the BRAS must remove it before sending out the packets. This task is accomplished through configuration of the vendor-tag strip command in BBA group configuration mode. Note that the vendor-tag strip command also removes the Circuit-ID tag.

SUMMARY STEPS

1. enable

2. configure terminal

3. bba-group pppoe {group-name | global}

4. vendor-tag strip

DETAILED STEPS

 
Command or Action
Purpose

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 

bba-group pppoe {group-name | global}

Example:

Router(config)# bba-group pppoe pppoe-group

Defines a PPPoE profile and enters BBA group configuration mode.

Step 4 

vendor-tag strip

Example:

Router(config-bba-group)# vendor-tag strip

Removes or strips the incoming Vendor-Specific Line-ID tag from outgoing PADO and PADR packets.

Note Starting in Cisco IOS Release 12.2(31)SB2, the vendor-tag strip command replaces the vendor-tag circuit-id strip command.

Troubleshooting Tips

When the radius-server attribute 31 remote-id global configuration command is entered in the PPPoE Agent Remote-ID Tag and DSL Line Characteristics Enhancement feature configuration on the BRAS, the debug radius privileged EXEC command can be used to generate a report that includes information about the incoming access interface, where discovery frames are received, and about the session being established in PPPoE extended NAS-Port format (format d).

Configuration Examples for the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

This section contains the following examples:

•Configuring PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement: Example

•Stripping Vendor-Specific Tags: Example

Configuring PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement: Example

In the following example, outgoing PADO and PADS packets will retain the incoming Vendor-Specific Circuit-ID tag: 

radius-server attribute 31 remote-id

!

bba-group pppoe rmt-id-tag

 vendor-tag remote-id service

 vendor-tag dsl-sync-rate service

 nas-port-id format c


!

interface FastEthernet0/0.1

 encapsulation dot1Q 120

 pppoe enable group rmt-id-tag

Stripping Vendor-Specific Tags: Example

In the following example, the BRAS will strip off incoming Vendor-Specific Circuit-ID tags from outgoing PADO and PADS packets: 

bba-group pppoe rmt-id-tag

 vendor-tag remote-id service

 vendor-tag strip 


interface FastEthernet0/0.1

 encapsulation dot1Q 120

 pppoe enable group rmt-id-tag

Additional References

The following sections provide references related to the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement feature.

Related Documents

Related Topic
Document Title

Configuring broadband and DSL

Cisco IOS Broadband and DSL Configuration Guide

RADIUS attributes

Cisco IOS Security Configuration Guide

DSL Line-ID tag solution

DSL Forum 2004-71: Solution for Remote-ID in PPPoE Discovery Phase

Migration to Ethernet-based DSL aggregation

DSL Forum Technical Report 101


Standards

Standard
Title

No new or modified standards are supported by this feature.

—


MIBs

MIB
MIBs Link

No new or modified MIBs are supported by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

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


RFCs


Technical Assistance

Description
Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/techsupport


Feature Information for PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

Table 1 lists the release history for this feature.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Table 1 Feature Information for PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement 

Feature Name
Releases
Feature Information

PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement

12.2(31)SB2
12.2(33)SRC
15.0(1)M

The PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement feature provides a method by which the digital subscriber line access multiplexer (DSLAM) sends the DSL Remote-ID tag in the discovery phase as an identifier for the authentication, authorization, and accounting (AAA) access request on an Ethernet interface, thereby simulating ATM-based broadband access, but using cost-effective Ethernet instead. This Remote-ID tag is useful for troubleshooting, authentication, and accounting.

In Cisco IOS Release 12.2(31)SB2, this feature was introduced.

The following commands were introduced or modified: vendor-tag circuit-id strip, vendor-tag remote-id service, vendor-tag strip.


Glossary

AAA—authentication, authorization, and accounting.

ATM—Asynchronous Transfer Mode.

BBA—broadband access.

BRAS—Broadband Remote Access Server.

DSLAM—digital subscriber line access multiplexer. A device that connects many digital subscriber lines to a network by multiplexing the DSL traffic onto one or more network trunk lines.

PADO—PPPoE Active Discovery Offer.

PADR—PPPoE Active Discovery Request.

PADS—PPPoE Active Discovery Session-Confirmation.

PPPoE—Point-to-Point Protocol over Ethernet.

RADIUS—Remote Authentication Dial-In User Service. Database for authenticating modem and ISDN connections and for tracking connection time.

VCI—virtual circuit identifier.

VLAN—virtual local-area network.

VPI—virtual path identifier.

VSA—vendor specific attribute. An attribute that has been implemented by a particular vendor. It uses the attribute Vendor-Specific to encapsulate the resulting AV pair: essentially, Vendor-Specific = protocol:attribute = value.

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