Broadband Network Gateway (BNG) is the access point for subscribers, through which they connect to the broadband network. When a connection is established between BNG and Customer Premise Equipment (CPE), the subscriber can access the broadband services provided by the Network Service Provide (NSP) or Internet Service Provider (ISP).

BNG establishes and manages subscriber sessions. When a session is active, BNG aggregates traffic from various subscriber sessions from an access network, and routes it to the network of the service provider.

BNG is deployed by the service provider and is present at the first aggregation point in the network, such as the edge router. An edge router, like the Cisco ASR 9000 Series Router, needs to be configured to act as the BNG. Because the subscriber directly connects to the edge router, BNG effectively manages subscriber access, and subscriber management functions such as:

• Authentication, authorization and accounting of subscriber sessions

• Address assignment

• Security

• Policy management

• Quality of Service (QoS)

Some benefits of using BNG are:

• The BNG router not only performs the routing function but also communicates with authentication, authorization, and accounting (AAA) server to perform session management and billing functions. This makes the BNG solution more comprehensive.

• Different subscribers can be provided different network services. This enables the service provider to customize the broadband package for each customer based on their needs.

The goal of the BNG architecture is to enable the BNG router to interact with peripheral devices (like CPE) and servers (like AAA and DHCP), in order to provide broadband connectivity to subscribers and manage subscriber sessions. The basic BNG architecture is shown in this figure.

The BNG architecture is designed to perform these tasks:

• Connecting with the Customer Premise Equipment (CPE) that needs to be served broadband services.

• Establishing subscriber sessions using IPoE or PPPoE protocols.

• Interacting with the AAA server that authenticates subscribers, and keeps an account of subscriber sessions.

• Interacting with the DHCP server to provide IP address to clients.

• Advertising the subscriber routes.

The five BNG tasks are briefly explained in the following sections.

The role of BNG is to pass traffic from the subscriber to the ISP. The manner in which BNG connects to the ISP depends on the model of the network in which it is present. There are two types of network models:

• Network Service Provider

• Access Network Provider

Network Service Provider

The following figure shows the topology of a Network Service Provider model.

In the Network Service Provider model, the ISP (also called the retailer) directly provides the broadband connection to the subscriber. As shown in the above figure, BNG is at the edge router, and its role is to connect to the core network through uplinks.

Access Network Provider

The following figure shows the topology of a Access Network Provider model.

In the Access Network Provider model, a network carrier (also called the wholesaler) owns the edge network infrastructure, and provides the broadband connection to the subscriber. However, the network carrier does not own the broadband network. Instead, the network carrier connects to one of the ISPs that manage the broadband network.

BNG is implemented by the network carrier and its role is to hand the subscriber traffic off to one of several ISPs. The hand-off task, from the carrier to the ISP, is implemented by Layer 2 Tunneling Protocol (L2TP) or Layer 3 Virtual Private Networking (VPN). L2TP requires two distinct network components:

• L2TP Access Concentrator (LAC)—The LAC is provided by the BNG.

• L2TP Network Server (LNS)—The LNS is provided by the ISP.

The BNG pie, asr9k-bng-px.pie can be installed and activated on the Cisco ASR 9000 Series Router to access the BNG features. The install, uninstall, activate and deactivate operations can be performed without rebooting the router.

It is recommended that the relevant BNG configurations be removed from the running configuration of the router, before uninstalling or deactivating the BNG pie.

Configuring BNG on the Cisco ASR 9000 Series Router involves these stages:

• Configuring RADIUS Server—BNG is configured to interact with the RADIUS server for authentication, authorization, and accounting functions. For details, see Configuring Authentication, Authorization, and Accounting Functions.

• Activating Control Policy—Control policies are activated to determine the action that BNG takes when specific events occur. The instructions for the action are provided in a policy map. For details, see Activating Control Policy.

• Establishing Subscriber Sessions—Configurations are done to set up one or more logical sessions, from the subscriber to the network, for accessing broadband services. Each session is uniquely tracked and managed. For details, see Establishing Subscriber Sessions.

• Deploying QoS—Quality of Service (QoS) is deployed to provide control over a variety of network applications and traffic types. For example, the service provider can have control over resources (example bandwidth) allocated to each subscriber, provide customized services, and give priority to traffic belonging to mission-critical applications. For details, see Deploying the Quality of Service (QoS).

• Configuring Subscriber Features—Configurations are done to activate certain subscriber features that provide additional capabilities like policy based routing, access control using access list and access groups, and multicast services. For details, see Configuring Subscriber Features.

• Verifying Session Establishment—Established sessions are verified and monitored to ensure that connections are always available for use. The verification is primarily done using "show" commands. Refer to the Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Command Reference guide for the list of various "show" commands.

To use a BNG command, you must be in a user group associated with a task group that includes the proper task IDs. The Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Command Reference guide includes the task IDs required for each command. If you suspect that the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

For specific hardware requirements for Cisco IOS XR 64-bit BNG, see Hardware Support for Cisco IOS XR 64-bit BNG.

These hardwares support BNG:

• The Satellite Network Virtualization (nV) system.

• The route switch processors, RSP-440, RSP-880 and RSP-880-LT-SE.

• The route processor, A99-RP-SE, A99-RP2-SE, on the Cisco ASR 9912 and the Cisco ASR 9922 chassis.

• The route switch processor, A99-RSP-SE, on the Cisco ASR 9910 and the Cisco ASR 9906 chassis.

• The below table lists the Line Cards and Modular Port Adapters that support BNG.

  Table 2. Line Cards and Modular Port Adapters Supported on BNG

  Product Description	Part Number
  24-Port 10-Gigabit Ethernet Line Card, Service Edge Optimized	A9K-24X10GE-SE
  36-Port 10-Gigabit Ethernet Line Card, Service Edge Optimized	A9K-36X10GE-SE
  40-Port Gigabit Ethernet Line Card, Service Edge Optimized	A9K-40GE-SE
  4-Port 10-Gigabit Ethernet, 16-Port Gigabit Ethernet Line Card, 40G Service Edge Optimized	A9K-4T16GE-SE
  Cisco ASR 9000 High Density 100GE Ethernet line cards: Cisco ASR 9000 8-port 100GE "LAN-only" Service Edge Optimized Line Card, Requires CPAK optics Cisco ASR 9000 8-port 100GE “LAN/WAN/OTN” Service Edge Optimized Line Card, Requires CPAK optics Cisco ASR 9000 4-port 100GE “LAN/WAN/OTN” Service Edge Optimized Line Card, Requires CPAK optics	A9K-8X100G-LB-SE A9K-8x100GE-SE A9K-4x100GE-SE
  Cisco ASR 9000 Series 24-port dual-rate 10GE/1GE service edge–optimized line cards	A9K-24X10-1GE-SE
  Cisco ASR 9000 Series 48-port dual-rate 10GE/1GE service edge–optimized line cards	A9K-48X10-1GE-SE
  80 Gigabyte Modular Line Card, Service Edge Optimized	A9K-MOD80-SE
  160 Gigabyte Modular Line Card, Service Edge Optimized	A9K-MOD160-SE
  20-Port Gigabit Ethernet Modular Port Adapter (MPA)	A9K-MPA-20GE
  ASR 9000 200G Modular Line Card, Service Edge Optimized, requires modular port adapters	A9K-MOD200-SE
  ASR 9000 400G Modular Line Card, Service Edge Optimized, requires modular port adapters	A9K-MOD400-SE
  2-port 10-Gigabit Ethernet Modular Port Adapter (MPA)	A9K-MPA-2X10GE
  4-Port 10-Gigabit Ethernet Modular Port Adapter (MPA)	A9K-MPA-4X10GE
  ASR 9000 20-port 10-Gigabit Ethernet Modular Port Adapter, requires SFP+ optics	A9K-MPA-20x10GE
  2-port 40-Gigabit Ethernet Modular Port Adapter (MPA)	A9K-MPA-2X40GE
  1-Port 40-Gigabit Ethernet Modular Port Adapter (MPA)	A9K-MPA-1X40GE
  ASR 9000 1-port 100-Gigabit Ethernet Modular Port Adapter, requires CFP2-ER4 or CPAK optics	A9K-MPA-1x100GE
  ASR 9000 2-port 100-Gigabit Ethernet Modular Port Adapter, requires CFP2-ER4 or CPAK optics	A9K-MPA-2x100GE

The BNG interoperability allows BNG to exchange and use information with other larger heterogeneous networks. These are the key features:

• BNG Coexists with ASR9001:

  ASR9001 is a standalone high processing capability router that comprises of a route switch processor (RSP), linecards (LC), and ethernet plugs (EPs). All BNG features are fully supported on the ASR9001 chassis.

• BNG Supports nV Satellite:

  • The only topology that BNG supports with nV Satellite is bundle access on the CPE side with non-bundle ICL links, as shown below:

    CPE --- Bundle --- [Satellite] --- Non Bundle ICL --- ASR9K

    For details on nV Satellite configuration, see nV System Configuration Guide for Cisco ASR 9000 Series Routers located here.

  • BNG does not support nV Satellite with bundle ICL and bundle access links, as shown below:

    CPE --- Bundle --- [Satellite] --- Bundle ICL --- ASR9K

  • From Cisco IOS XR Software Release 6.1.2 and later, BNG supports the use of Cisco NCS 5000 Series satellite.

  • From Cisco IOS XR Software Release 6.2.2 and later, Cisco IOS XR 32 bit operating system supports BNG geo redundancy with Cisco NCS 5000 Series satellite. Whereas, it does not support BNG geo redundancy with Cisco ASR 9000v satellite. For details, see BNG Geo Redundancy chapter in this guide..

• BNG interoperates with Carrier Grade NAT (CGN):

  To address the impending threat from IPv4 address space depletion, it is recommended that the remaining or available IPv4 addresses be shared among larger numbers of customers. This is done by using CGN, which primarily pulls the address allocation to a more centralized NAT in the service provider network. NAT44 is a technology that uses CGN and helps manage depletion issues of the IPv4 address space. BNG supports the ability to perform NAT44 translation on IPoE and PPPoE-based BNG subscriber sessions.

  Note	For BNG and CGN interoperability, configure the BNG interface and the application service virtual interface (SVI) on the same VRF instance.

BNG supports Cisco Smart Software Licensing that provides a simplified way for the customers to purchase licenses and to manage them across their network. Smart licensing provides a customizable consumption-based model that aligns to the network growth of the customer. It also provides the flexibility to quickly modify or upgrade software feature configurations to deploy new services over time.

Router# show sessionmon license statistics

                Active Standby
                =============
Peak (24 hours) 32000     1

The Broadband Network Gateway (BNG) functionality is supported on Cisco IOS XR 64-bit ASR 9000 Series Routers, in addition to the Cisco IOS XR 32-bit ASR 9000 Series Routers. This functionality is available on Cisco ASR 9000 Series Routers with RSP880, RSP 880-LT and Cisco ASR 9000 High Density 100GE Ethernet line cards (LCs) having more CPU cycles and per-process virtual memory, which in turn increases the scale and performance of the Cisco ASR 9000 Series Router as a BNG.