Information Technology Reference
In-Depth Information
remote (called) phone. The RTP voice streams extend from each phone across the WAN to
the other phone. Figure 10-7 illustrates call flow in a distributed deployment.
Route Pattern
WAN
FAILURE
Phones
De-Register
From CUCM
CUCM
Uses
CFUR
Phones
Register
With SRST
PSTN
Figure 10-6
WAN Failure to SRST/CFUR
Call Manager
Call Manager
ICT
H.323
SIP
SCCP/SIP
SCCP/SIP
RTP
Figure 10-7
Distributed Deployment Call Flow CUCM Call-Routing Components
The signaling protocols available include Inter-Cluster Trunk (ICT), H.323, and Session Ini-
tiation Protocol (SIP). The CUCM clusters at each site control their local phones using
Skinny Client Control Protocol (SCCP) or SIP. The use of gatekeepers (along with a well-
designed dial-plan) allow scalability to thousands of sites, with either a full CUCM cluster
for large sites or a CUCME for smaller sites (third-party solutions may also be integrated).
PSTN backup for WAN failure is achieved using a hierarchical dial-plan, and gatekeeper
CAC may be used when WAN bandwidth for calls is not available.
Note:
Location-based CAC does not work in a distributed deployment because the clus-
ters do not communicate their current bandwidth utilization to other clusters. Instead,
Gatekeeper CAC provides a centralized service to track available bandwidth between clus-
ters and trigger AAR when necessary. Gatekeeper is a router IOS feature set that may be
configured on one or more gateway routers in the system.
