Information Technology Reference
In-Depth Information
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Minimize jitter, congestion, and packet loss for Intra-Cluster Communication Signaling (ICCS).
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Provision bandwidth between servers in accordance with expected call volume and device types/numbers.
During (at least) the initial deployment phase for CUCM, CUCM commonly must coexist with a traditional PBX infrastructure.
There are two common approaches to migration from a PBX infrastructure to IP telephony:
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Phased migration:
In this case, there is a small initial IP telephony deployment, and connectivity between CUCM and the
PBX is provided via a VoIP gateway, using T1/E1 CAS/analog or T1/E1 PRI.
The signaling protocol chosen for connectivity can include regular PRI, QSIG PRI, SIP, or H.323. QSIG allows the greatest
level of feature transparency between CUCM and PBX.
The migration itself takes place in several phases, with users being gradually moved over from the PBX to CUCM.
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Parallel cutover:
This migration approach involves the deployment of a complete, parallel IP telephony infrastructure,
including the placement of a second (IP) phone on each user's desk. The legacy PBX and infrastructure can be left in place
until the IP telephony infrastructure is proven to operate correctly and users have developed a high degree of confidence in it.
Codecs and Regions
In a VoIP network, calls typically have to transit both LAN links, where bandwidth is usually abundant, and WAN links, where
it usually is not. Different codecs often have different associated bandwidth requirements, and in CUCM, it is possible to specify
which type of audio and video codecs should be used when voice traffic transit links between different parts of the network using a
mechanism called
regions
.
One method of implementing CAC with CUCM is to use
locations
. Locations CAC is dependent on regions because regions
control the particular codec and the amount of bandwidth that needs to be allocated for a call when voice traffic crosses the network.
Locations CAC is described in the section, “Call Admission Control,” later in this e-book.
