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PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement
Information About the PPPoE Agent Remote-ID and DSL Line Characteristics Enhancement
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PPPoE Agent Remote ID and DSL Line Characteristics Enhancement
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).
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
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.
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 PPP
over Ethernet (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.
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 PPP
over Ethernet (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
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
.
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.
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
DSLAM
Subscriber
lines
ATM
network
BRAS
To IP network
and RADIUS
server
1
42354
DSLAM
Subscriber
lines
Ethernet
connectivity from
DSLAM to BRAS
DSLAM to BRAS
BRAS
To IP network
and RADIUS
server
142355
DSLAM intercepts discovery packets and inserts a unique PPPoE Line-ID
tag to PADI or PADR packets and forwards upstream to BRAS.
tag to PADI or PADR packets and forwards upstream to BRAS.
BRAS processes the tag and extracts the Remote-ID, which is stored on
the session.
the session.
The Remote-ID is sent as a NAS-Port-ID attribute in AAA accounting and
PPP authentication requests.
PPP authentication requests.