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Cisco IP Telephony Solution Reference Network Design
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Chapter 1 IP Telephony Deployment Models
Clustering Over the IP WAN
Figure 1-5
Local Failover Model with Two Sites
In summary, observe the following guidelines when implementing the local failover model:
·
Configure each site to contain at least one primary Cisco CallManager subscriber and one backup
subscriber.
·
Configure Cisco CallManager groups and device pools to allow devices within the site to register
with only the servers at that site under all conditions.
·
Cisco highly recommends that you replicate key services (TFTP, DNS, DHCP, LDAP, and IP Phone
Services), all media resources (conference bridges and music on hold), and gateways at each site to
provide the highest level of resiliency. You could also extend this practice to include a voice mail
system at each site. Under a WAN failure condition, only sites without access to the publisher
database might loose a small amount of functionality.
·
Every 10,000 busy hour call attempts (BHCA) in the cluster requires 900 kbps of bandwidth for
Intra-Cluster Communication Signaling (ICCS). This is a minimum bandwidth requirement, and
bandwidth is allocated in multiples of 900 kbps.
WAN
M
M
M
M
IP
V
Site A
Publisher/TFTP server
Sub A
Sub B
Backup
Sub A
Sub B
Backup
Site B
Gateway
Voice Mail
Server
MOH
JTAPI
IP-AA/IVR
IP Phone
Conf
Xcode
TAPI
SoftPhone
M
M
M
IP
V
Gateway
Voice Mail
Server
MOH
JTAPI
IP-AA/IVR
IP Phone
Conf
Xcode
TAPI
SoftPhone
V
V
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