Cisco ASR 9000 Series Configuration Manual page 66

Subscriber Session Overview
• Establishing a connection—in this phase CPE finds the BNG with which to communicate.
• Authenticating and authorizing the subscriber—in this phase, BNG authenticates the subscribers and
authorizes them to use the network. This phase is performed with the help of the RADIUS server.
• Giving subscriber an identity—in this phase, the subscriber is assigned an identity, the IP address.
• Monitoring the session—in this phase, BNG ascertains that the session is up and running.
The subscribers are not configured directly on BNG. Instead, a framework is created on which subscriber
features and subscriber sessions are started and stopped dynamically. The framework consists of control
policies and dynamic templates, which perform these functions:
• Control policy determines the action BNG takes when specific events, such as receipt of a session start
request, or failure of authentication, occurs. The action is determined by the class-map defined in the
control policy. The action involves activating dynamic templates.
• Dynamic template contains a set of CLI commands that are applied to a subscriber session. Multiple
dynamic templates can be activated, one at a time, on the same subscriber interface. Also, the same
dynamic template can be activated on multiple subscriber interfaces through different control policies.
Service providers can deploy subscribers over VLAN in these ways:
• 1:1 VLAN model—This model depicts a scenario where one dedicated VLAN is available for each
customer. Each VLAN is an q-in-q VLAN where the inner VLAN tag represents the subscriber and the
outer VLAN tag represents the DSLAM.
• N:1 VLAN model—This model depicts a scenario where multiple subscribers are available on a shared
VLAN. The VLAN tags represent the DSLAM or the aggregation device.
• Ambiguous VLANs —This model allows the operator to specify a large number of VLANs in a single
CLI line. Using ambiguous VLAN, a range of inner or outer tags (or both) can be configured on a VLAN
sub-interface. This is particularly useful for the 1:1 model, where every subscriber has a unique value
for the set of VLAN tags. For more information about ambiguous VLANs, see
Ambiguous VLANs , on page
The subscriber sessions are established over the subscriber interfaces, which are virtual interfaces. It is possible
to create only one interface for each subscriber session. A port can contain multiple VLANs, each of which
can support multiple subscribers. BNG creates subscriber interfaces for each kind of session. These interfaces
are named based on the parent interface, such as bundle-ether 2.100.pppoe312. The subscribers on bundles
(or bundle-VLANs) interfaces allow redundancy, and are managed on the BNG route processor (RP).
To provide network redundancy and load balancing, the service provider can deploy multiple links between
the DSLAM and the BNG. The individual links can be grouped into ether-bundles, including VLANs over
ether-bundles, or link aggregation groups (LAGs). The subscriber sessions can be active on any link within
the bundle or group. If a BNG is deployed in a LAG configuration, all traffic for one subscriber should be
configured to traverse one link of the ether-bundle. Load-balancing is achieved by putting different subscribers
on different links.
There are two mechanisms to establish a subscriber session, namely, IPoE and PPPoE. These are discussed
next in the next topics.
Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,
Release 4.2.x
56
138.
Establishing Subscriber Sessions
Subscriber Session on
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