ATM for Subscriber Access Overview

Supported Configurations for ATM Subscriber Access

On MX Series routers with MPC/MIC interfaces that use the ATM MIC with SFP (Model Number MIC-3D-8OC3-2OC12-ATM), you can create the following configurations to enable subscribers to access the router over an ATM network using ATM Adaptation Layer 5 (AAL5) permanent virtual connections (PVCs):

• PPP-over-Ethernet-over-ATM

• Routed IP-over-ATM

• Bridged IP-over-Ethernet-over-ATM

• PPP-over-ATM

• Concurrent PPP-over-Ethernet-over-ATM interfaces and IP-over-Ethernet-over-ATM interfaces on a single ATM PVC

PPP-over-Ethernet-over-ATM Configurations

PPP-over-Ethernet-over-ATM (PPPoE-over-ATM) configurations support both statically created and dynamically created PPPoE (pp0) logical subscriber interfaces over static ATM underlying interfaces. Most PPPoE and subscriber services features supported on terminated connections and tunneled (L2TP access concentrator, or LAC) connections are also supported for access to an MX Series router over an ATM network.

PPPoE-over-ATM configurations require static configuration of the underlying ATM physical interface and ATM logical interface. You can configure the PPPoE (pp0) subscriber interface either dynamically, by means of a dynamic profile, or statically. You must also configure the ATM underlying interface with PPPoE-over-ATM logical link control (LLC) encapsulation (encapsulation ppp-over-ether-over-atm-llc).

Using dynamic PPPoE-over-ATM configurations for ATM subscriber access enables you to configure an MX Series router to dynamically create PPPoE logical subscriber interfaces over static ATM underlying interfaces only when needed; that is, when a subscriber logs in on the associated underlying interface. Dynamic PPPoE over static ATM configurations are not supported on M Series routers and T Series routers.

Optionally, you can dynamically or statically apply subscriber services such as class of service (CoS) and firewall filters to the PPPoE (pp0) subscriber interface. For PPPoE-over-ATM configurations that create a dynamic PPPoE subscriber interface, you can configure CoS attributes and firewall filters in the dynamic profile that defines the pp0 subscriber interface. For PPPoE-over-ATM configurations that create a static PPPoE subscriber interface, you can statically configure CoS attributes and firewall filters as you would for any static interface configured on an MX Series router.

Routed IP-over-ATM Configurations

Routed IP-over-ATM (IPoA) configurations support statically created IPv4 and IPv6 logical subscriber interfaces over static ATM underlying interfaces. IPoA configurations are typically used to implement business digital subscriber line (DSL) connections that do not require connection negotiation for address assignment.

IPoA configurations require static configuration of the ATM underlying interface, IPv4 interface, IPv6 interface, CoS attributes, and firewall fiters. Dynamic configuration of these components is not supported.

To configure IPoA subscriber access, specify either of the following encapsulation types on the ATM underlying interface:

• For IPoA encapsulation with logical link control (LLC), configure ATM subnetwork attachment point (SNAP) encapsulation (encapsulation atm-snap).

• For IPoA encapsulation with virtual circuit (VC) multiplexing, configure ATM VC multiplex encapsulation (encapsulation atm-vc-mux).

Optionally, you can statically configure subscriber services such as CoS and firewall filters and apply them to the IPv4 or IPv6 interface; you cannot use a dynamic profile for this purpose.

Bridged IP-over-Ethernet-over-ATM Configurations

Bridged IP-over-Ethernet-over-ATM (IPoE-over-ATM) configurations support statically created IPv4 and IPv6 logical subscriber interfaces over static ATM underlying interfaces. Like IPoA configurations, IPoE-over-ATM configurations are typically used in topologies that do not require connection negotiation for address assignment.

For bridged IP-over-Ethernet-over-ATM configurations on an MX Series router, you must configure the ATM underlying interface with Ethernet-over-ATM LLC encapsulation (encapsulation ether-over-atm-llc).

IPoE-over-ATM configurations require static configuration of the ATM underlying interface, IP interface, CoS attributes, and firewall fiters. Dynamic configuration of these components is not supported. Optionally, you can statically configure subscriber services such as class of service (CoS) and firewall filters and apply them to the IPv4 or IPv6 interface; you cannot use a dynamic profile for this purpose.

PPP-over-ATM Configurations

PPP-over-ATM (PPPoA) configurations support statically created PPP logical subscriber interfaces over static ATM underlying interfaces. Most features supported for PPPoE configurations are also supported for PPP access to an MX Series router over an ATM network.

PPPoA configurations require static configuration of the ATM underlying interface and PPP subscriber interface.

To configure PPPoA subscriber access, you must configure either of the following encapsulation types on each PPP logical subscriber interface:

• For PPPoA encapsulation with logical link control (LLC), configure PPP-over-AAL5 LLC encapsulation (encapsulation atm-ppp-llc).

• For PPPoA encapsulation with virtual circuit (VC) multiplexing, configure PPP-over-AAL5 multiplex encapsulation (encapsulation atm-ppp-vc-mux).

Optionally, you can use dynamic profiles to dynamically or statically apply subscriber services, such as CoS attributes and firewall filters, to the static PPP subscriber interface. Configuring CoS and firewall filters in this manner enables you to efficiently and economically provide these services to PPP subscribers accessing the router over an ATM network.

Concurrent PPP-over-Ethernet-over-ATM and IP-over-Ethernet-over-ATM Configurations

You can configure subscriber interfaces for both PPPoE-over-ATM and IPoE-over-ATM concurrently on a single ATM PVC. IPoE-over-ATM includes support for both IPv4-over-Ethernet-over-ATM interfaces and IPv6-over-Ethernet-over-ATM interfaces.

In concurrent PPPoE-over-ATM and IPoE-over-ATM configurations, you define the ATM logical interface with IPoE-over-ATM encapsulation and specify PPPoE-over-ATM as a supported family. The PPPoE-over-ATM underlying interface with IPoE-over-ATM encapsulation processes PPPoE Discovery packets to establish the PPPoE session. When the PPPoE-over-ATM session is established, the router processes PPPoE-over-ATM session packets and applies PPPoE-over-ATM–specific features on the PPPoE-over-ATM session interface.

To configure concurrent PPPoE-over-ATM and IPoE-over-ATM subscriber interfaces on a single ATM PVC, you configure the ATM logical interface with Ethernet-over-ATM LLC encapsulation (encapsulation ether-over-atm-llc). You then configure PPPoE-over-ATM as a supported family. When the router detects the IPoE-over-ATM encapsulation and PPPoE-over-ATM as a supported family, it identifies the configuration as concurrently supporting both PPPoE-over-ATM and IPoE-over-ATM on the same ATM PVC.

The concurrent PPPoE-over-ATM and IPoE-over-ATM configuration supports all features specific to PPPoE-over-ATM interfaces and IPoE-over ATM interfaces, with no changes. These features include the following:

• Class of service (CoS)

• Traffic control profiles with ATM virtual path (VP) shaping and ATM virtual circuit (VC) shaping

• Firewall filters

• PPPoE-over ATM L2TP access concentrator (LAC) support

• Interface statistics

• PPPoE-over-ATM statistics

• Graceful Routing Engine switchover (GRES)

• Unified in-service software upgrade (unified ISSU)

• Dynamic Address Resolution Protocol (ARP)

• Framed IP addresses and address-assignment pools

Configuration and Encapsulation Types for ATM Subscriber Access

You use the same basic statements, commands, and procedures to create, verify, and manage PPPoE-over-ATM, IPoA, IPoE-over-ATM, and PPPoA configurations as the statements, commands, and procedures you use for static configurations on M Series routers and T Series routers, and for dynamic PPPoE configurations on MX Series routers.

A critical element of configuring ATM subscriber access is ensuring that you specify the correct encapsulation type for the ATM logical interface. The encapsulation type you use depends on the supported configuration and, for IPoA and PPPoA configurations, whether you want to configure an encapsulation type that uses logical link control (LLC) or virtual circuit (VC) multiplexing.

ATM Virtual Path Shaping on ATM MICs with SFP

On MX Series routers with Modular Port Concentrator (MPC) interfaces and an ATM Modular Interface Card (MIC) with small form-factor pluggable transceiver (SFP) installed, you can configure class of service (CoS) hierarchical shaping for the traffic carried on an ATM virtual path (VP). Traffic shaping helps you manage and regulate the traffic flow in your network by shaping the traffic on the VP to a specified rate. With traffic shaping, you can better control the traffic flow to avoid network congestion, and ensure that the traffic adheres to the class-of-service policies you set for it.

To configure hierarchical VP shaping on an ATM MIC with SFP (Model number MIC-3D-8OC3-2OC12-ATM), you must configure an interface set that consists of the ATM logical interface units on the ATM physical interface. The members of the interface set must all share the same virtual path identifier (VPI) and have different virtual circuit identifiers (VCIs). You then define one or more CoS traffic control profiles that include the ATM service category (atm-service) and the peak cell rate (peak-rate), sustained cell rate (sustained-rate), and maximum burst size (max-burst-size) parameters.

The ATM service category works in conjunction with the peak cell rate, sustained cell rate, and maximum burst size ATM cell parameters to shape the traffic leaving the interface. Finally, you apply a specified traffic control profile to the output traffic at the interface set and at each of its member ATM logical interfaces.

In the queueing model used for ATM VP hierarchical shaping on ATM MICs with SFP, the ATM physical interface functions as a level 1 scheduler node, the interface set containing the ATM logical interfaces functions as a level 2 scheduler node, and the ATM logical interfaces function as level 3 scheduler nodes.

The following configuration requirements apply to ATM VP shaping on ATM MICs with SFP:

• All ATM interfaces that belong to the same interface set must share the same virtual path identifier (VPI) and have a unique virtual circuit identifier (VCI).

• The ATM interface set can include only ATM interfaces. It cannot include Ethernet interfaces.

• The ATM interface set cannot include PPPoE over ATM interfaces, but it can include the underlying ATM interface over which PPPoE over ATM is carried.