Cisco ASR 5000 Series User Manual

Packet Data Interworking Function Overview
Features and Functionality - Licensed Enhanced Feature Support ▀
Cisco ASR 5000 Series Product Overview ▄
OL-22938-02
Network
Entity
Consideration in Two-Chassis Configuration
IPMS Server
Each chassis is connected to an independent IPMS Server. When a switchover takes place, the new IPMS Server
continues to capture and store the call logs (signaling messages and events).
O&M
Device
Each chassis is connected to an independent O&M Device. When a switchover takes place, the new O&M Device
continues to perform the function as the original device was configured.
Session Recovery Support
The session recovery feature provides seamless failover and almost instantaneous reconstruction of subscriber session
information in the event of a hardware or software fault within the same chassis, preventing a fully connected user
session from being dropped.
Session recovery is performed by mirroring key software processes (the session manager and the AAA manager, for
example) within a single PDIF. These mirrored processes remain in an idle state (in standby mode), wherein they
perform no processing, until they may be needed in the case of a software failure (a session manager task aborts, for
example). The system spawns new instances of standby mode sessions and AAA managers for each active Control
Processor (CP) being used.
Additionally, other key system-level software tasks such as VPN manager are performed on a physically separate Packet
Services Card (PSC/PSC2) to ensure that a double software fault (the session manager and the VPN manager fail at
same time on same card, for example) cannot occur. The PSC used to host the VPN manager process is in active mode
and is reserved by the operating system for this sole use when session recovery is enabled.
The additional hardware resources required for session recovery include a standby System Management Card (SMC)
and a standby PSC.
There are two modes for session recovery.
Task recovery mode: Wherein one or more session manager failures occur and are recovered without the need
to use resources on a standby PSC. In this mode, recovery is performed by using the mirrored standby-mode
session manager tasks running on active PSCs. The standby-mode task is renamed, made active, and is then
populated using information from other tasks such as AAA manager.
Full PSC recovery mode: Used when a PSC hardware failure occurs, or when a PSC migration failure happens.
In this mode, the standby PSC is made active and the standby-mode session manager and AAA manager tasks
on the newly-activated PSC perform session recovery.
Session/call state information is saved in the peer AAA manager task because each AAA manager and session manager
task is paired together. To ensure task recovery, these pairs are started on physically different PSCs.
Important: For more information on session recovery support, refer to Session Recovery in the System Enhanced
Feature Configuration Guide.

Cisco ASR 5000 Series Specifications

General

Brand	Cisco
Model	ASR 5000 Series
Category	Network Router
Language	English