ANCP Agent Neighbors and Operations

Overview

ANCP acts as a control plane between a service-oriented Layer 3 edge device and a Layer 2 access node. The access nodes—ANCP neighbors—are network devices that terminate access loops from subscribers; for DSL access loops, the access node is a DSL access multiplexer (DSLAM). Queuing and scheduling mechanisms for subscriber traffic must avoid congestion within the access network while contending with multiple flows and distinct CoS requirements. These mechanisms require the edge device—a router acting as a broadband network gateway (BNG), often also called a network access server (NAS)—to provide information about the access network and subscriber traffic.

The ANCP agent can map an access line to an interface or interface set either statically or dynamically. The agent provides that information to both CoS and AAA. The agent passes on to both CoS and AAA the traffic shaping attributes for each subscriber access line that the access node sent to the ANCP agent. In addition, the agent sends to AAA all DSL Forum attributes that were sent by the access node. AAA can use these attributes during RADIUS accounting and authentication for both DHCP IP demux and PPPoE subscriber sessions. The traffic rates can also be used for shaping L2TP tunnel traffic.

You can monitor ANCP agent events and operations by including the traceoptions statement at the [edit protocols ancp] hierarchy level.

Junos OS supports Class of Service (CoS) traffic shaping on the following interface types for ANCP:

• Static VLAN interfaces, except those created by Extensible Subscriber Services Manager (ESSM)

• Static VLAN demux interfaces, except those created by ESSM

• Static interface sets, including those created by ESSM

• Dynamic interface sets

• Dynamic VLAN-tagged interface sets

• Dynamic agent circuit identifier (ACI) interface sets, also known as ACI sets or ACI VLANs

• Dynamic PPPoE and DHCP IP demux subscriber interfaces

• Dynamic VLAN demux interfaces with Ethernet-VPLS encapsulation

ANCP was developed as an extension of RFC 3292, General Switch Management Protocol (GSMP) V3, but is now defined in RFC 6320, Protocol for Access Node Control Mechanism in Broadband Networks.

Topology Discovery

The router uses topology discovery to collect information from the access node. The information includes the following:

• Topology of the access network

• DSL line state

• Actual upstream and downstream net data rates of a synchronized DSL link

• Maximum attainable upstream and downstream net data rates

• Interleaving delay

Subscriber Services

The router receives the service profile for the subscribers from a RADIUS server. Most of the services are enforced by the router itself. The router shapes the aggregate egress traffic to subscribers based on the local loop throughput reported by the DSLAM. This traffic shaping optimizes traffic flow while avoiding traffic drops in the access node.

Some service attributes, such as interleaving delay and multicast channel information, are enforced at the access node. The ANCP agent provides the line configuration mechanism that the edge device can use to pass the line configuration to the access nodes. Typically, multiple profiles are provisioned on the access node. The router instructs the access node which profile to use for a given subscriber.

Subscribers typically receive some combination of voice, data, and video services. Each service can be provisioned on a VLAN. A subscriber might receive only a single service over a single VLAN configured on a logical interface. A group of VLANs carrying services to a subscriber is an interface set.

Subscribers have operational states, but they do not have administrative states because they cannot be configured in the CLI.

Subscribers have one of the following operational states which represent the DSL line state as it is reported in the ANCP Port Up and Port Down messages sent by an access node:

• Idle—Ports are not configured and the subscriber cannot log in.

• Silent—Ports are configured and the subscriber is connected, but the DSL modem is not ready to transfer data.

• Showtime—Ports are configured, the subscriber is connected, and the DSL modem is online and ready to transfer data.

ANCP Interfaces and Access Loop Circuit Identifiers

The access loop or access line in an ANCP topology consists of the physical elements between the subscriber device (CPE) and the access node. An identifier associated with the access loop serves to identify the subscriber as well. This identifier is an alphanumeric string that actually identifies the interface on the DSLAM from which subscriber requests originate. It can be referred to by various names.

• In ANCP messages, a TLV carries the access loop circuit ID, also referred to as the access line identifier, access loop circuit identifier, or access identifier.

• DHCP discovery packets can identify the line with the Agent Circuit ID suboption in the Option 82 field.

• PPPoE discovery packets can identify the line with the Agent-Circuit-ID subattribute in the DSL Forum vendor-specific tag.

Each of these identifiers is abbreviated as ACI. When the ANCP agent receives a port management message from an access node, it uses the access loop circuit identifier contained in the message to determine which logical interface or interface set corresponds to the subscriber.

You can associate an identifier with an ANCP access line by static configuration. When you configure a logical interface by specifying the interface name at the [edit protocols ancp interfaces] hierarchy level, include the access-identifier statement to associate the access loop circuit identifier with the interface. When you configure an interface set by including the interface-set statement at the [edit protocols ancp interfaces] hierarchy level, associate the access loop circuit identifier with the interface set by including the access-identifier statement at the [edit protocols ancp interfaces interface-set interface-set-name] hierarchy level.

When the DHCP or PPPoE discovery packet includes an ACI, the ANCP agent can dynamically map the ACI to the subscriber interface or interface set. VLANs for the subscribers are created according to a dynamic profile; these are called agent circuit identifier-based or ACI-based dynamic VLANs.

ANCP agent support for RADIUS authentication and accounting requires that both static and dynamic ACIs must be unique across the network. No two interfaces across multiple neighbors (access nodes) can share the same identifier. The DHCP and PPPoE processes do not have information about the access node IP addresses and consequently cannot distinguish between duplicate identifiers. This situation prevents the AAA services framework from correlating a DHCP or PPPoE client session with an access line for RADIUS authentication and accounting.

Mapping Access Lines to Interfaces and Interface Sets

The ANCP agent maps the ACI for subscriber access lines to an interface or interface set to apply DSL attributes received from the access node to CoS traffic shaping for the access line. The access line mapping can be statically configured with the access-identifier statement, or dynamically derived during subscriber authentication. Static mapping always supersedes dynamic mapping.

The ANCP agent can remap an access line to a different interface or interface set than its original mapping. Remapping can also be static or dynamic. For example, an access line might be first dynamically mapped to a subscriber interface and then statically configured to an interface set.

You can statically configure mapping with the statement only for interface and interface set types that have configured or deterministic names:

• Static VLAN interfaces

• Static VLAN demux interfaces

• Static interface sets

• Dynamic interface sets

• Dynamic VLAN-tagged interface sets

Static configuration with the statement is required for mapping an access line to static interface sets, dynamic interface sets, and dynamic VLAN-tagged interface sets. This is true regardless of the presence of an ACI in the PPPoE or DHCP IP demux subscriber’s discovery packet, because the use of the ACI is irrelevant to the creation of these types of interface sets.

You cannot statically configure mapping with the statement for the following interface and interface set types, because they have nondeterministic, automatically generated names:

• Dynamic VLAN demux interfaces

• Dynamic ACI interface sets (ACI VLANs)

• Dynamic PPPoe and DHCP IP demux subscriber interfaces

In the context of Layer 2 wholesale services, the ANCP agent can map access lines to dynamic VLAN demux interfaces that have Ethernet-VPLS encapsulation. The ANCP agent triggers the creation of these interfaces with the ANCP Port UP message, which always includes the ACI for the access line. The agent can then dynamically map the interface to an access line for CoS traffic shaping.

Dynamic mapping works as follows:

• If the subscriber interface is a member of an interface set, the ANCP agent maps the ACI for the access line to the interface set.

• If the subscriber interface is not a member of an interface set, the ANCP agent maps the ACI for the access line to the subscriber interface.

The ANCP agent does not support static or dynamic mapping for the following interface types, regardless of the presence of the access line’s ACI in the subscriber’s discovery packet:

• Static VLAN interfaces created by ESSM.

• Static VLAN demux interfaces created by ESSM.

• Dynamic VLAN interfaces.

• Dynamic VLAN demux interfaces that do not have Ethernet-VPLS encapsulation.

ANCP Neighbors

The ANCP agent can report traffic only for access nodes that are configured as ANCP neighbors (also referred to as ANCP peers). Neighbors can establish TCP connections with the router. Include the neighbor statement at the [edit protocols ancp] hierarchy level to configure an access node as an ANCP neighbor.

The ANCP agent exchanges adjacency messages with neighbors. If an adjacency message is not received from a neighbor within the expected period, then the neighbor is considered to be down and is disconnected. You can adjust how long the ANCP agent waits for adjacency messages from all neighbors by including the adjacency-timer statement at the [edit protocols ancp] hierarchy level. The interval between adjacency messages is negotiated between router and the neighbor during adjacency establishment. The larger of two timer values—either the value received in the ANCP SYN message or the configured value—is selected. Loss of synchronization between the router and a neighbor is declared when no valid messages are received for a period of time that exceeds three times the negotiated value.

ANCP neighbors have one of the following administrative states, which simply represent the configuration of the neighbor:

• enabled—The neighbor is configured in the CLI.

• disabled—The neighbor is not configured, meaning either that it has never been configured or that the configuration has been deleted.

ANCP neighbors in the enabled state have one of the following operational states, which represent the state of adjacency negotiations:

• Configured—The neighbor has been configured, but has never established an adjacency.

• Establishing—Adjacency negotiations are in progress.

• Established—Adjacency negotiations have succeeded and an ANCP session has been established.

• Not Established—The neighbor has lost a previously established adjacency, but is ready to begin negotiations.

You can also configure parameters for a specific neighbor that override global or default configurations by including any of the following statements at the [edit protocols ancp neighbor ip-address] hierarchy level:

• adjacency-timer—Adjust the interval between adjacency messages exchanged with this neighbor.

• ietf-mode—Prevent the ANCP agent from operating in a backward-compatible mode for this neighbor; for neighbors that use the current IETF implementation of ANCP.

• maximum-discovery-table-entries—Specify how many discovery table entries are accepted from this neighbor. Include this statement at the [edit protocols ancp] hierarchy level to set the number of entries globally for all neighbors.

• pre-ietf-mode—Enable the ANCP agent to operate in a backward-compatible mode for this neighbor; for neighbors that use the original IETF implementation of ANCP (GSMPv2) rather than the current implementation. Include this statement at the [edit protocols ancp] hierarchy level to operate in backward-compatible mode globally for all neighbors.

RFC 6320, Protocol for Access Node Control Mechanism in Broadband Networks, defines ANCP Version 1. ANCP was originally implemented based on General Switch Management Protocol (GSMP) version 3, sub-version 1. However, the Internet community has made so many extensions and modifications to GSMPv3 in the course of developing ANCP that ANCP is no longer interoperable with GSMPv3. Consequently, ANCP neighbors must be able to dynamically detect the version that each peer supports. A joint registry codifies the GSMP and ANCP version numbers.

When an ANCP neighbor opens adjacency negotiations, it indicates the highest version of ANCP that it supports, either 0x31 for GSMPv3 or 0x32 for ANCP Version 1. (Version 1 may also be called Version 50, referring to the decimal conversion from the hexadecimal value.) If the receiving neighbor supports that version of ANCP, it returns that value when it responds to the sending neighbors. If it does not support that version, the receiving neighbor simply drops the message.

The ANCP agent stores information about active ANCP subscribers in the Junos shared database, including DSL attributes for the access lines. This storage is persistent and is removed from the database only when you delete the interface or interface set for the access line or issue one of the following commands:

• clear ancp neighbor

• clear ancp subscriber

The persistence of the storage enables PPPoE and DHCP IP demux subscribers to be properly managed by RADIUS for authentication and accounting, with their DSL attributes, even when the ANCP connection has been temporarily terminated.

Partitions

ANCP supports the division of an access node into logical partitions. Each partition creates an adjacency with a router; each partition on an access node can form adjacencies with different routers. Partition negotiation takes place during ANCP adjacency negotiation. ANCP messages carry the following fields relating to the partition negotiation:

• The partition type (PType) field indicates whether the access node is partitioned and how the partition identifier is negotiated. The field has one of the following values negotiated during the formation of the adjacency:

  • 0—The access node is not partitioned or does not support partitions.

  • 1—The number of partitions is fixed and the router requests the access node to use the identifier it places in the partition identifier field.

  • 2—The number of partitions is fixed and the access node has assigned the partition identifier.

• The partition ID field that indicates one of the following scenarios for ANCP agent support of the neighbor:

  • Zero partition ID—The ANCP agent supports each neighbor on an IP address over a single TCP session with a partition ID of zero. This is the default support case. This value is required when the partition type is zero.

  • Single nonzero partition ID—The ANCP agent supports each neighbor on an IP address over a single TCP session with a nonzero partition ID. This case requires partition ID learning to be enabled with the gsmp-syn-wait statement at the [edit protocols ancp] hierarchy level.

• The partition flag (PFlag) field indicates the type of partition request being made. A value of one specifies a new adjacency.

The following partitioning schemes are supported

• Each partition has an independent ANCP session and channel to an adjacent router. All partitions have a fixed partition ID of zero.

• Each partition has an independent ANCP session and channel to an adjacent router. Each partition has a dedicated, nonzero partition ID.

Adjacency Update Messages

After an adjacency has been established, the ANCP agent uses adjacency update messages to inform routers that control the same partition about each other. Once more than one router has established an adjacency to a given partition, the ANCP agent sends an adjacency update message to each of these routers to report how many established adjacencies the partition currently supports. When an adjacency is lost, an update message is sent to the remaining routers to report the change in status. You can use the show ancp neighbor detail command to display the number of adjacencies currently established on a particular partition.

Generic Response Messages and Result Codes

ANCP neighbors and the router can reply to messages either with a specific response message or a generic response message. A generic response message is typically sent when no information needs to be sent to the peer other than a success or failure result. If the response is about a failure, then a result code is included that specifies the kind of failure; a limited amount of diagnostic data can also be included. A generic response message can also be sent independently of a request if the adjacency is being shut down because of the failure. In this case, the sender of the message zeros out the Transaction ID field in the message header and the Message Type field in the Status-Info TLV.

Table 1 describes the result codes that can be included in a generic response message.

Generic response messages usually include the Status-Info TLV, which includes supplemental information about a warning or error condition. The Status-Info TLV is required when the result code indicates any of the following: a port is down or does not exist, a mandatory TLV is missing, or a TLV is invalid. The Status-Info TLV can also be included in other ANCP message types.

Benefits of Access Node Control Protocol

• Simplify the configuration and maintenance of access lines between access nodes and subscribers.

• Perform CoS-related adjustments on upstream and downstream data rate attributes to both accurately provide services and control congestion in the network.

• Provide access network information, such as DSL attributes to backend applications such as operations support systems (OSS) for service management.

• Store DSL attributes in the session database for use during RADIUS authentication and accounting of PPPoE sessions.

1:1 and N:1 Traffic Shaping Models

The 1:1 and N:1 traffic shaping models determine how VLANs are correlated with households. These models are also referred to as access models or configuration models. A network can include one or both of the models:

• 1:1 model—A household has only one PPPoE or DHCP IP demux subscriber session. One or more such households can exist on a single VLAN or VLAN demux interface. In the case of a single household, either the subscriber interface or its underlying VLAN or VLAN demux interface can represent the household. In the case of multiple households, the corresponding subscriber interfaces represent the households. In either case, the interface representing a household must be mapped to the ACI for its access line.

  Table 2 describes the types of interfaces supported for the ANCP 1:1 access model when interface sets are not involved, and whether the PPPoE or DHCP IP demux discovery packets must include the ACI for the subscriber access lines.

  Table 2: ACI Mapping by Interface Type for the ANCP 1:1 Model

  Interface Type	Description	Presence of ACI in Discovery Packets
  Dynamic PPPoE or DHCP IP demux interface	When ACI is present in discovery packets, the ANCP agent maps the ACI to the subscriber interface. The name of the interface is automatically generated and nondeterministic.	Required.
  Static VLAN or VLAN demux interface	The name of the interface is statically configured. The ANCP agent configuration must include the access-identifier statement to statically map the ACI to the interface.	Not present.

• N:1 model—A household can have more than one PPPoE or DHCP IP demux subscriber session. The household can have more than one VLAN or VLAN demux interface. In either case, all the interfaces must be grouped into an interface set. The interface set in turn must be mapped to the ACI for the household’s access line.

  An interface set groups the dynamic PPPoE or DHCP IP demux sessions for a household. The subscribers are placed into interface sets by one several methods. Table 3 describes the types of interface sets supported in the ANCP N:1 access model, how they are created, and how the ACI is mapped to the interface set.

  Table 3: ACI Mapping by Interface Set Type for the ANCP N:1 Access Model

  Type of Interface Set	Description	Interface Type	Presence of ACI in Discovery Packets
  ACI-based VLAN interface sets	When the router receives a DHCP or PPPoE discovery packet that includes an ACI embedded within the DSL Forum vendor-specific tag, it dynamically creates the VLAN and the interface set. The router generates a nondeterministic name for the interface set, such as aci-1003-ge-1/0/0.1073741832. The ANCP agent automatically maps the ACI from the discovery packet to the dynamically created interface set. All DHCP IP demux or PPPoE sessions that have the same ACI are mapped to the same interface set.	Dynamic VLAN and VLAN demux interfaces.	Required.
  Dynamic interface sets	A dynamic profile dynamically creates the interface set and places interfaces in the set. The profile can either have the name of the interface set explicitly configured or a variable that represents the interface set name. If a variable is used, then the interface set name is provided by RADIUS when it returns an Access-Accept message for the subscriber. The ANCP agent configuration must include the access-identifier statement to statically map the ACI to the interface set. All DHCP IP demux and PPPoE sessions are mapped to an interface set according to the rules of the dynamic profile.	DHCP IP demux subscriber interfaces, PPPoE subscriber interfaces, or VLAN interfaces.	Irrelevant.
  Static interface sets	The interface set and set name are statically configured and include multiple static interfaces. The ANCP agent configuration must include the access-identifier statement to statically map the ACI to the interface set.	Static VLAN and VLAN demux interfaces.	Irrelevant.
  VLAN-tagged interface sets	When the router receives a DHCP or PPPoE discovery packet that includes a VLAN ID, it dynamically creates the VLAN and the interface set. The interface set is given a deterministic name consisting of the physical interface name and the VLAN tags, for example, ge-1/0/0-101. The ANCP agent configuration must include the access-identifier statement to statically map the ACI to the interface set. All DHCP IP demux or PPPoE sessions that have the same VLAN ID tag are mapped to the same interface set.	Dynamic VLAN and VLAN demux interfaces.	Irrelevant.

CoS traffic shaping is based on the subscriber downstream traffic rate that the ANCP agent receives from the access node and then passes to CoS. CoS can shape subscriber traffic at the level of the household or the session:

• Household shaping—Only aggregate traffic to the household is shaped. Household shaping results from applying a CoS traffic-control profile to the static VLAN or VLAN demux interface or to the interface set.

• Session shaping—The traffic rate to individual devices in the household is shaped. Session shaping results from specifying a CoS traffic-control profile in the dynamic PPPoE profile that creates the subscriber session. Depending on the network configuration, session shaping may employ shared priority queues to shape all sessions identically or individual priority queues to shape the sessions separately.

Business Services Traffic Shaping Model

In addition to the N:1 and 1:1 traffic shaping models, the ANCP agent also supports a business services traffic shaping model. In this model, the Extensible Subscriber Services Manager (ESSM) classifies a PPPoE session as either residential household or business subscriber. Classification occurs during RADIUS authentication and authorization. The ANCP agent applies CoS traffic shaping differently depending on the classification.

Before RADIUS authentication and authorization, the PPPoE session represents a residential household in the ANCP 1:1 model. The ANCP agent dynamically maps the household’s access line to the corresponding subscriber interface and applies CoS traffic shaping to that interface. The household line’s ACI is present in the PPPoE discovery packet.

When ESSMD subsequently classifies a PPPoE session as a business subscriber session during RADIUS authentication and authorization, it creates and groups multiple management and data plane static VLAN interfaces into a static interface set. then it statically maps the access line for the PPPoE session to this interface set according to the CLI configuration. The ANCP agent removes CoS traffic shaping from the subscriber interface and applies it to the static interface set. Removing the CoS traffic shaping means that the CoS application applies the next rate in its default or configured adjustment control profile to the interface or interface set. The new business subscriber interface set cannot contain a mix of static and dynamic interfaces. That prohibition is not limited to dynamic VLANs and the PPPoE session that triggered the creation of the interface set.

From the perspective of the ANCP agent, the business dervices model effectively overrides a dynamically derived access-line-to-interface mapping with a statically configured access-line-to-interface-set mapping. This action triggers the ANCP agent to reapply CoS traffic shaping accordingly.

The business services model is typically used in a Layer 2 wholesale network. For detailed information, see Layer 2 Wholesale with ANCP-Triggered VLANs Overview.

ANCP Network Using N:1 and 1:1 Configuration Models without Interface Sets

In this sample topology, two households are configured for one underlying static VLAN or VLAN demux interface (N:1; dual-tagged VLAN) and a single household is configured for another underlying interface (1:1; single-tagged VLAN) (Figure 1). In addition to the unique ACI assigned by the access node, each household is further identified by the VLAN, which is mapped to the identifier in the ANCP agent configuration. CoS traffic shaping for sessions can employ only shared priority queues to shape all sessions identically; individual priority queues to shape the sessions separately are not supported.

Figure 1: Sample ANCP Topology Without Interface Sets (1:1 and N:1 Model)

Sequence of ANCP Events: Static VLAN or VLAN Demux Interfaces over Ethernet Without Interface Sets

The following sequence of events is for the topology in Figure 1 with static VLAN interfaces over Ethernet without interface sets.

1. A network device in the household initiates PPPoE discovery.

2. PPPoE creates a dynamic PPPoE session on the underlying static VLAN or VLAN demux interface and applies the advisory options configured on the VLAN to the session.

3. The access node independently provides the ANCP agent with the ANCP DSL attributes for an access line identified by an ACI.

4. The ANCP agent sends CoS the adjusted downstream data rate for the static VLAN or demux VLAN mapped to the ACI. The ANCP agent stores all DSL attributes, including the adjusted upstream data rate, in the router’s shared database.

5. AAA correlates the dynamic PPPoE session with the access line by matching the underlying interface of the session to the static VLAN or VLAN demux interface associated with the ACI in the ANCP agent configuration.

6. AAA retrieves the ANCP DSL attributes for the access line from the router’s shared database and maps them to the Juniper Networks DSL VSAs in the RADIUS Access-Request and Accounting-Request messages. If the DSL attributes are unavailable, the session’s advisory upstream and downstream data rates are mapped to the Upstream-Calculated-Qos-Rate VSA (26-142) and Downstream-Calculated-Qos-Rate (26–141) VSAs, respectively. These VSAs are then included in the RADIUS messages.

ANCP Network Using N:1 Configuration Model with Interface Sets

In this topology, multiple households are configured for each underlying static VLAN or VLAN demux interface (Figure 2). The VLANs are dual-tagged. Each household includes several CPE devices that access the Internet. In addition to the unique ACI assigned by the access node, the household is further identified by the interface set. The interface set groups the dynamic PPPoE sessions for the individual subscriber devices. It is either explicitly configured in the dynamic PPPoE profile or specified in the RADIUS Access-Accept message during PPPoE session authentication. Session shaping can employ shared priority queues to shape all sessions identically or individual queues to shape the sessions separately.

Figure 2: Sample ANCP Topology with Interface Sets (N:1 Model)

In this N:1 model with interface sets, the access node must add the DSL Forum VSA to the PPPoE PADI and PADR discovery packets that it passes to the router during the establishment of dynamic PPPoE sessions. The VSA includes the ACI for the household. This inclusion enables AAA to correlate the PPPoE sessions with their respective subscriber access lines and DSL attributes during RADIUS authentication and accounting. If the ACI is not present, AAA cannot make the correlation and subsequently reports only the advisory upstream and downstream data rates to RADIUS Authentication and Accounting.

When the dynamic PPPoE profile is configured with the $junos-interface-set-name predefined variable, the configuration of the access node, router, and RADIUS server must be synchronized with regard to the ACI and interface set:

• The RADIUS Access-Accept message must contain the Juniper Networks Qos-Interface-Set-Name VSA (26-130).

• The CoS Layer 2 configuration must explicitly identify the interface set that is named in the Qos-Interface-Set-Name VSA (26-130).

• The ANCP agent configuration must map an ACI to the interface set that is named in the Qos-Interface-Set-Name VSA (26-130).

Sequence of ANCP Events: Static VLAN Interfaces over Ethernet with Interface Sets

The following sequence of events is for the topology in Figure 2 with static VLAN interfaces over Ethernet with interface sets.

1. A network device in the household initiates PPPoE discovery.

2. The access node adds the DSL Forum VSA tag with the ACI for the household to the PPPoE PADI and PADR discovery packets. (The identifier is known to PPPoE as the agent circuit identifier.)

3. PPPoE creates a dynamic PPPoE session with the provided ACI on the underlying static VLAN and applies the advisory options configured on the VLAN to the session.

4. The access node independently provides the ANCP agent with the ANCP DSL attributes for an access line identified by an ACI.

5. The ANCP agent provides CoS with the adjusted downstream data rate for the interface set mapped to the ACI. The ANCP agent stores all ANCP DSL attributes, including the adjusted upstream and downstream data rates, in the router’s shared database.

6. AAA correlates the dynamic PPPoE session with the access line by matching the session identifier received in the DSL Forum VSA to the ACI configured for the interface set in the ANCP agent configuration.

7. AAA retrieves the ANCP DSL attributes for the access line from the router’s shared database and maps them to the Juniper Networks DSL VSAs in the RADIUS Access-Request and Accounting-Request messages. If the DSL attributes are unavailable, the session’s advisory upstream and downstream data rates are mapped to the Upstream-Calculated-Qos-Rate VSA (26-142) and Downstream-Calculated-Qos-Rate (26–141) VSAs, respectively. These VSAs are then included in the RADIUS messages.

8. When authentication is completed, the dynamic PPPoE session is placed into the interface set configured in the dynamic PPPoE profile. The profile specifies a named interface set or the $junos-interface-set-name predefined variable, which indicates that the interface set is named in the RADIUS Access-Accept message.

ANCP Network Using 1:1 Configuration Model with Interface Sets

In this topology, a single household is configured for each underlying static VLAN or VLAN demux interface (Figure 3). The VLANs are dual-tagged. Each household includes several CPE devices that access the Internet. In addition to the unique ACI assigned by the access node, the household is further identified by the interface set. The interface set is either explicitly configured in the dynamic PPPoE profile or specified in the RADIUS Access-Accept message during PPPoE session authentication. Session shaping can employ shared priority queues to shape all sessions identically or individual queues to shape the sessions separately.

Figure 3: Sample ANCP Topology with Interface Sets (1:1 Model)

In this 1:1 model with interface sets, the ANCP agent configuration must map the underlying interface for the PPPoE sessions in an interface set to both the ACI and the interface set. This configuration enables AAA to correlate the PPPoE sessions with their respective subscriber access lines and DSL attributes during RADIUS authentication and accounting.

When the dynamic PPPoE profile is configured with the $junos-interface-set-name predefined variable, the configuration of the access node, router, and RADIUS server must be synchronized with regard to the ACI and interface set:

• The RADIUS Access-Accept message must contain the Juniper Networks Qos-Interface-Set-Name VSA (26-130).

• The CoS Layer 2 configuration must explicitly identify the interface set that is named in the Qos-Interface-Set-Name VSA (26-130).

• The ANCP agent configuration must map an ACI to the interface set that is named in the Qos-Interface-Set-Name VSA (26-130).

Sequence of ANCP Events: Static VLAN Demux Interfaces over Aggregated Ethernet with Interface Sets

The following sequence of events is for the topology in Figure 3 with static VLAN demux interfaces over aggregated Ethernet with interface sets.

1. A network device in the household initiates PPPoE discovery.

2. PPPoE creates a dynamic PPPoE session with the provided ACI on the underlying static VLAN demux interface and applies the advisory options configured on the VLAN to the session.

3. The access node independently provides the ANCP agent with the ANCP DSL attributes for an access line identified by an ACI.

4. The ANCP agent provides CoS with the adjusted downstream data rate for the interface set mapped to the ACI. The ANCP agent stores all ANCP DSL attributes, including the adjusted upstream and downstream data rates, in the router’s shared database.

5. AAA correlates the dynamic PPPoE session with the access line by matching the underlying interface of the session to the underlying interface configured for the interface set in the ANCP agent configuration.

6. AAA retrieves the ANCP DSL attributes for the access line from the router’s shared database and maps them to the Juniper Networks DSL VSAs in the RADIUS Access-Request and Accounting-Request messages. If the DSL attributes are unavailable, the session’s advisory upstream and downstream data rates are mapped to the Upstream-Calculated-Qos-Rate VSA (26-142) and Downstream-Calculated-Qos-Rate (26–141) VSAs, respectively. These VSAs are then included in the RADIUS messages.

7. When authentication is completed, the dynamic PPPoE session is placed into the interface set configured in the dynamic PPPoE profile. The profile specifies a named interface set or the $junos-interface-set-name predefined variable, which indicates that the interface set is named in the RADIUS Access-Accept message.