Stateful Line Module Switchover For Lns Sessions - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - BROADBAND ACCESS CONFIGURATION GUIDE 2010-10-12 Configuration Manual

JunosE 11.3.x Broadband Access Configuration Guide

Stateful Line Module Switchover for LNS Sessions

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Accounting statistics reported in RADIUS octet counts (Acct-Input-Octets and
Acct-Output-Octets) for tunneled PPP customers at the L2TP LAC exclude the
following data:
LCP when Proxy LCP is enabled and accepted at the LNS
Initial PPP PAP request
Initial PPP CHAP challenge and response
Accounting statistics reported in RADIUS packet counts (Acct-Input-Packets and
Acct-Output-Packets) for tunneled PPP customers at the L2TP LAC are based on
packets delivered to or received from the L2TP session. These statistics exclude L2TP
control traffic and L2TP hello messages.
For information on accounting statistics for terminated PPP sessions, see the PPP
Accounting Statistics section in JunosE Link Layer Configuration Guide .
In releases in which the stateful line module switchover feature is not available or in
scenarios in which this behavior is disabled, a reload of the line module disconnects user
sessions and disrupts traffic forwarding through it. In a network in which an E120 or E320
router that contains the Service IOA functions as the LNS device on one side of the L2TP
tunnel, the LNS is the logical termination point of a PPP connection that is being tunneled
from the remote system by the LAC. A LAC receives packets from a remote client and
forwards them to an LNS on a remote network. All the tunneled sessions terminate on
the LNS to provide enhanced performance during decapsulation and encapsulation of
packets, and fragmentation and reassembly of tunneled packets. If the line module in
the LNS that performs the traffic processing encounters a fault, such as a hardware or
software error, all the active subscriber sessions are disconnected.
Stateful switchover of LNS sessions avoids subscriber disconnections during the
switchover of the line module installed on the LNS device (tunnel server module or ES2-S1
Service IOA on ES2 4G LMs in this case). You can enable high availability for the line
module pairs using the mode high-availability slot command in Redundancy
Configuration mode. This command enables you to specify the slots in which the tunnel
server line modules that you want to be configured as the primary and secondary modules
reside. If HA is active between these modules, the secondary module becomes the primary
when the assigned primary module fails. The newly active primary module retains all the
subscribers that were active and were managed by the previously configured primary
module without requiring the subscribers to be reconnected. The failure of the tunnel
server module in the LNS device and the switchover from a defective module to a newly
active primary module in a seamless, undisrupted manner for subscribers is transparent
to the end users.
Line module high availability uses a 1:1 redundancy model to maintain subscriber sessions,
and this functionality is supported only on E120 and E320 routers installed with ES2 4G
LMs and Service IOAs. This feature is supported only for PPP-based stacks (such as
L2TP, PPP, and IP) and not for other applications such as GRE.
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