The ICSR feature
provides the highest possible availability for continuous call processing without
interrupting subscriber services. ICSR allows the operator
to configure geographically distant gateways for redundancy purposes. In
the event of a gateway failure, ICSR allows sessions to
be transparently routed around the failure, thus maintaining
the user experience. ICSR also preserves session information and
ICSR between two StarOS instances running on separate servers for
services that support ICSR in the same StarOS release. For
combination VMs where more than one service type is in use, only
those services that support ICSR can make use of ICSR.
ICSR can provide redundancy
for site/row/rack/host outages and major
software faults. The two StarOS instances must be run on
non-overlapping hosts and network interconnects. ICSR
is only supported between identically configured VPC-SI
both L2 and L3 ICSR.
ICSR is implemented through
the use of redundant chassis. The chassis are configured
as primary and backup, with one being active and one standby. Both
chassis are connected to the same AAA server. A checkpoint
duration timer controls when subscriber data is sent from the active
chassis to the standby chassis. If the active chassis handling
the call traffic goes out of service, the standby chassis
transitions to the active state and continues processing the call
traffic without interrupting the subscriber session.
The chassis determine
which is active through a proprietary TCP-based connection
known as the Service Redundancy Protocol (SRP) link. The
SRP link is used to exchange Hello messages between the primary
and backup chassis and must be maintained for proper system operation. For
additional information, refer to the Session Recovery chapter.
ICSR licenses are currently
supported for the following services:
L2TP Access Concentrator (LAC) functionality
for ICSR is supported by the following protocol and services:
Access Concentrator (LAC) functionality for ICSR
is not supported
by the following service:
GPRS Support Node
Data Network Gateway
- SAE-GW System
Architecture Evolution Gateway
Network Server (LNS) functionality for ICSR is not supported
by any services.
For releases prior to
17.0, ICSR should not be configured
on chassis supporting L2TP calls.
support for LAC requires a separate LAC license, as well
as an Inter-Chassis Session Recovery license.
Contact your Cisco
account representative to verify whether a specific service supports ICSR
as an option.