Cisco Cisco Unified Contact Center Enterprise 9.0(1) Folheto

Individually, the private and visible networks can fail with limited impact to the Unified CCE agents and 
calls. However, if both of these networks fail at the same time, the system will be reduced to very limited 
functionality. This failure should be considered catastrophic and should be avoided by careful WAN 
design, with backup and resiliency built into the design.

If both the visible and private networks fail at the same time, the following conditions apply:

The Unified CM subscribers will detect the failure and continue to function locally, with no impact 
to local call processing and call control. However, any calls that were set up and are sending the 
active voice path media over the visible WAN link will fail with the link. When the call fails, the 
Unified CCE PG will see the call drop and will write a Termination Call Detail (TCD) record in the 
ICM database for that call at the time it is dropped.

The Call Routers and Peripheral Gateways will detect the private network failure after missing five 
consecutive TCP keep-alive messages. These TCP keep-alive messages are generated every 100 ms, 
and the failure will be detected within about 500 ms on this link.

The Call Routers will attempt to contact their Peripheral Gateways with the test-other-side message 
to determine if the failure was a network issue or if the remote Call Router had failed and was no 
longer able to send TCP keep-alive messages. The Call Routers determine which side will continue 
to be active (typically, this would be the A-Side of the system because it is the side with the most 
active Peripheral Gateway connections), and that side will stay active in simplex mode while the 
remote Call Router and PGs will be in isolated-disabled mode. The Call Routers will send a message 
to the Peripheral Gateways to realign their data feeds to the active Call Router only.

The Peripheral Gateways will determine which side has the active Unified CM connection. 
However, it will also consider the state of the Call Router, and the Peripheral Gateway will not 
remain active if it is not able to connect to an active Call Router. Typically, this will force the A-Side 
PGs into active simplex enabled mode and the B-Side into isolated-disabled.

The surviving Call Router and Peripheral Gateways will detect the failure of the visible network by 
the loss of TCP keep-alives on the visible network. These keep-alives are sent every 400 ms, so it 
can take up to two seconds before this failure is detected.

The Call Router will be able to see only the local Peripheral Gateways, which are those used to 
control local Unified IP IVRs or Unified CVP Call Servers and the local half of the Unified CM 
cluster. The remote Unified IP IVRs or CVP Call Servers will be off-line with no Unified ICM Call 
Control via the GED-125 IVR PG interface. The Unified ICM Call Routing Scripts automatically 
routes around these off-line devices using the peripheral-on-line status checks. Calls that were in 
progress in the off-line IP-IVRs will either drop or use the local default script in the IP-IVR or the 
Call Forward on Error settings in Unified CM. Calls under Unified CVP control from the off-line 
Call Servers will get treatment from the survivability TCL script in their ingress voice gateways.   
For calls that were in progress but are no longer visible to Unified CCE, a Termination Call Detail 
(TCD) record is written to the ICM database for the call data up to the time of the failure. If the 
default or survivability scripts redirect the calls to another active Unified CCE component, the call 
will appear as a "new call" to the system, with no relationship to the original call for reporting or 
tracking purposes.

Any new calls that come into the disabled side will not be routed by the Unified CCE, but they can 
be redirected or handled using standard Unified CM redirect on failure for their CTI route points or 
the Unified CVP survivability TCL script in the ingress voice gateways.

Agents will be impacted as noted above if their IP phones are registered to the side of the 
Unified CM cluster opposite the location of their active Peripheral Gateway and CTI OS Server 
connection. Only agents that were active on the surviving side of the Peripheral Gateway with 
phones registered locally to that site will not be impacted.