Cisco ASR 5000 Series, Обзор продукта

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Session Control Manager Overview
▀ Features and Functionality - Licensed Enhanced Feature Support
▄ Cisco ASR 5000 Series Product Overview
OL-22938-02
Features and Functionality - Licensed Enhanced Feature
Support
This section describes optional enhanced features and functions.
Each of the following optional enhanced features require the purchase of an additional license to implement the
functionality with the SCM.
Important:
For more information about enhanced features in this section, refer to the System Enhanced Feature
Configuration Guide .
Interchassis Session Recovery
The ASR 5000 provides industry leading carrier class redundancy. The systems protects against all single points of
failure (hardware and software) and attempts to recover to an operational state when multiple simultaneous failures
occur.
The system provides several levels of system redundancy:
Under normal N+1 PSC/PSC2 hardware redundancy, if a catastrophic packet processing card failure occurs all
affected calls are migrated to the standby packet processing card if possible. Calls which cannot be migrated
are gracefully terminated with proper call-termination signaling and accounting records are generated with
statistics accurate to the last internal checkpoint
If the Session Recovery feature is enabled, any total packet processing card failure will cause a packet
processing card switchover and all established sessions for supported call-types are recovered without any loss
of session.
Even though Cisco Systems provides excellent intra-chassis redundancy with these two schemes, certain catastrophic
failures which can cause total chassis outages, such as IP routing failures, line-cuts, loss of power, or physical
destruction of the chassis, cannot be protected by this scheme. In such cases, the Interchassis Session Recovery feature
provides geographic redundancy between sites. This has the benefit of not only providing enhanced subscriber
experience even during catastrophic outages, but can also protect other systems such as the RAN from subscriber re-
activation storms.
The Interchassis Session Recovery feature allows for continuous call processing without interrupting subscriber
services. This is accomplished through the use of redundant chassis. The chassis are configured as primary and backup
with one being active and one in recovery mode. A checkpoint duration timer is used to control when subscriber data is
sent from the active chassis to the inactive chassis. If the active chassis handling the call traffic goes out of service, the
inactive chassis transitions to the active state and continues processing the call traffic without interrupting the subscriber
session. The chassis determines which is active through a propriety TCP-based connection called a redundancy link.
This link is used to exchange Hello messages between the primary and backup chassis and must be maintained for
proper system operation.
Interchassis Communication