Cisco Unified Contact Center Enterprise Solution Reference ...
Cisco Unified Contact Center Enterprise Solution Reference ...
Cisco Unified Contact Center Enterprise Solution Reference ...
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Peripheral Gateway Design Considerations<br />
Scenario 2: Visible Network Fails<br />
3-32<br />
<strong>Cisco</strong> <strong>Unified</strong> <strong>Contact</strong> <strong>Center</strong> <strong>Enterprise</strong> 7.x SRND<br />
Chapter 3 Design Considerations for High Availability<br />
Note The terms public network and visible network are used interchangeably throughout this document.<br />
The visible network in this design model is the network path between the data center locations where the<br />
main system components (<strong>Cisco</strong> <strong>Unified</strong> CallManager subscribers, Peripheral Gateways,<br />
<strong>Unified</strong> IP IVR/<strong>Unified</strong> CVP components, and so forth) are located. This network is used to carry all the<br />
voice traffic (RTP stream and call control signaling), <strong>Unified</strong> ICM CTI (call control signaling) traffic,<br />
as well as all typical data network traffic between the sites. In order to meet the requirements of<br />
<strong>Cisco</strong> <strong>Unified</strong> CallManager clustering over the WAN, this link must be highly available with very low<br />
latency and sufficient bandwidth. This link is critical to the <strong>Unified</strong> CCE design because it is part of the<br />
fault-tolerant design of the system, and it must be highly resilient as well:<br />
The highly available (HA) WAN between the central sites must be fully redundant with no single<br />
point of failure. (For information regarding site-to-site redundancy options, refer to the WAN<br />
infrastructure and QoS design guides available at http://cisco.com/go/srnd.) In case of partial failure<br />
of the highly available WAN, the redundant link must be capable of handling the full central-site<br />
load with all QoS parameters. For more information, see the section on Bandwidth Requirements<br />
for <strong>Unified</strong> CCE Clustering Over the WAN, page 11-17.<br />
A highly available (HA) WAN using point-to-point technology is best implemented across two<br />
separate carriers, but this is not necessary when using a ring technology.<br />
If the visible network fails between the data center locations, the following conditions apply:<br />
The <strong>Cisco</strong> <strong>Unified</strong> CallManager subscribers will detect the failure and continue to function locally,<br />
with no impact to local call processing and call control. However, any calls that were set up over this<br />
WAN link will fail with the link.<br />
The <strong>Unified</strong> ICM Call Routers will detect the failure because the normal flow of TCP keep-alives<br />
from the remote Peripheral Gateways will stop. Likewise, the Peripheral Gateways will detect this<br />
failure by the loss of TCP keep-alives from the remote Call Routers. The Peripheral Gateways will<br />
automatically realign their data communications to the local Call Router, and the local Call Router<br />
will then use the private network to pass data to the Call Router on the other side to continue call<br />
processing. This does not cause a failover of the Peripheral Gateway or the Call Router.<br />
Agents might be affected by this failure under the following circumstances:<br />
– If the agent desktop (<strong>Cisco</strong> Agent Desktop or CTI OS) is registered to the Peripheral Gateway<br />
on side A of the system but the physical phone is registered to side B of the <strong>Cisco</strong> <strong>Unified</strong><br />
CallManager cluster.<br />
Under normal circumstances, the phone events would be passed from side B to side A over the<br />
visible network via the CTI Manager Service to present these events to the side A Peripheral<br />
Gateway. The visible network failure will not force the IP phone to re-home to side A of the<br />
cluster, and the phone will remain operational on the isolated side B. The Peripheral Gateway<br />
will no longer be able to see this phone, and the agent will be logged out of <strong>Unified</strong> CCE<br />
automatically because the system can no longer direct calls to the agent's phone.<br />
– If the agent desktop (<strong>Cisco</strong> Agent Desktop or CTI OS) and IP phone are both registered to<br />
side A of the Peripheral Gateway and <strong>Cisco</strong> <strong>Unified</strong> CallManager, but the phone is reset and it<br />
re-registers to a side B of the <strong>Cisco</strong> <strong>Unified</strong> CallManager subscriber.<br />
If the IP phone re-homes or is manually reset and forced to register to side B of a <strong>Cisco</strong> <strong>Unified</strong><br />
CallManager subscriber, the <strong>Cisco</strong> <strong>Unified</strong> CallManager subscriber on side A that is providing<br />
the CTI Manager service to the local Peripheral Gateway will unregister the phone and remove<br />
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