Provisioning Ppp Lac Session - Cisco ASR 9000 Series Configuration Manual

Provisioning PPP LAC Session

Provisioning PPP LAC Session
In a PPP LAC session, the PPP session is tunneled to a remote network server by BNG, using Layer 2 Tunneling
Protocol (L2TP). BNG performs the role of L2TP Access Concentrator (LAC), as it puts the subscriber session
in the L2TP tunnel. The device on which the tunnel terminates is called L2TP Network Server (LNS). During
a PPP LAC session, the PPPoE encapsulation terminates on BNG; however, the PPP packets travel beyond
BNG to LNS through the L2TP tunnel. A typical LAC session is depicted in Figure 1.
Figure 7: LAC Session
The PPP LAC session is used in the Access Network Provider (wholesale) model, where the network service
provider (NSP) is a separate entity from the local access network provider (ANP). NSPs perform access
authentication, manage and provide IP addresses to subscribers, and are responsible for overall service. The
ANP is responsible for providing the last-mile digital connectivity to the customer, and for passing on the
subscriber traffic to the NSP. In this kind of setup, the ANP owns the LAC and the NSP owns the LNS.
A PPP LAC session establishes a virtual point-to-point connection between subscriber device and a node in
the service provider network. The subscriber dials into a nearby L2TP access connector (LAC). Traffic is then
securely forwarded through the tunnel to the LNS, which is present in service provider network. This overall
deployment architecture is also known as Virtual Private Dial up Network (VPDN).
Reassembly of fragmented L2TP data packets is enabled on LAC to prevent these packets from getting
dropped. See,
A PPP LAC session supports stateful switchover (SSO) along with non-stop routing (NSR) to reduce traffic
loss during RP failover. For more information, see
103
The process of provisioning a PPP LAC session involves:
• Defining a template with specific settings for the VPDN. See,
• Defining the maximum number of VPDN sessions that can be established simultaneously. See,
• Activating the logging of VPDN event messages. See,
• Specifying the method to apply calling station-ID. See,
• Specifying the session-ID. See,
• Defining specific settings for the L2TP class. See,
Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,
Release 4.3.x
100
L2TP Reassembly on LAC, on page 101
page 106.
Configuring Maximum Simultaneous VPDN Sessions, on page
ID, on page 111.
L2TP Access Concentrator Stateful Switchover, on page
Activating VPDN Logging, on page
Configuring Options to Apply on Calling Station
Configuring L2TP Session-ID Commands, on page
Configuring L2TP Class Options, on page
Establishing Subscriber Sessions
Configuring the VPDN Template, on
108.
112.
110.
114.
OL-28375-03