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High Availability
Method
Method
Scalability Method
Path
H.323 Service sends a
connect failure message
back to IVR Service,
which sends a failure back
to Unified ICME.
connect failure message
back to IVR Service,
which sends a failure back
to Unified ICME.
Survivability of Existing Calls
The sections above touch on high availability with respect to handling of new incoming calls
in the face of failed components. In this section we discuss the handling of existing calls when
components fail.
in the face of failed components. In this section we discuss the handling of existing calls when
components fail.
Table 12: High Availability Call Survivability
Existing calls experience this…
If this component fails…
Call is lost. [SIP or H.323]
Ingress Gateway
If single Proxy Server, call will be lost. But if proxy pair is
deployed, further SIP messaging will simply go through the
deployed, further SIP messaging will simply go through the
SIP Proxy Server
other Proxy Server in the pair. Even if failure occurs during
an Invite transaction, the Ingress Gateway will time-out
waiting for a response and continue the transaction with the
other Proxy Server in the pair.
an Invite transaction, the Ingress Gateway will time-out
waiting for a response and continue the transaction with the
other Proxy Server in the pair.
Media path remains connected to the VXML Gateway or
to the agent, but signaling through the SIP and IVR Services
to the agent, but signaling through the SIP and IVR Services
Call Server (SIP Service)
is lost. If connected to the VXML Gateway, the IOS Voice
Browser will time-out, but will not be able to inform the
Ingress Gateway of the failure. The Ingress Gateway will
time-out either its SIP session timer or its RTP media
inactivity timer and invoke the Survivability script.
Browser will time-out, but will not be able to inform the
Ingress Gateway of the failure. The Ingress Gateway will
time-out either its SIP session timer or its RTP media
inactivity timer and invoke the Survivability script.
If connected to an agent, the parties can continue talking
for some time. The RTP media inactivity timer will not
expire, but the SIP session timer will time-out and try to
"refresh" the session. This involves a new Invite transaction,
which, if the Call Server came back up in the meantime,
will succeed and essentially restart the call. If refreshing
fails, then the call is dropped.
for some time. The RTP media inactivity timer will not
expire, but the SIP session timer will time-out and try to
"refresh" the session. This involves a new Invite transaction,
which, if the Call Server came back up in the meantime,
will succeed and essentially restart the call. If refreshing
fails, then the call is dropped.
[SIP]
VRU PG
ICM Service sends a state change event of partial service.
IVR Service sends the partial service state change to the
IOS Voice Browser in a long-poll response. IVR Service
sends a 5xx response to any pending or new request from
the IOS Voice Browser. If that causes the call to be dropped,
the SIP Service will be notified by the Ingress Gateway and
IVR Service sends the partial service state change to the
IOS Voice Browser in a long-poll response. IVR Service
sends a 5xx response to any pending or new request from
the IOS Voice Browser. If that causes the call to be dropped,
the SIP Service will be notified by the Ingress Gateway and
Planning Guide for Cisco Unified Customer Voice Portal Cisco Unified Customer Voice Portal 4.1(1)
63
Chapter 6: Creating a Failover Strategy (Designing for High Availability)
Survivability of Existing Calls