Cisco CallManager
The CallManager is, in simplistic terms, the traditional PBX component of the
Cisco IPCC. It is currently either supplied as a software-only solution for supported
hardware platforms, or as a hardware/software Cisco solution.The hardware
requirements will be discussed in more detail later in the chapter.
The CallManager does not, as such, have any Automatic Call Distributor
(ACD) functionality, but rather relies on other applications to provide these features
in addition to other advanced functionality.The CallManager has the ability
to provide the information for one phone to call another (not necessarily an IP
phone). It maintains the dial plans, phone information (such as where a particular
extension can or cannot call), and has the capability to manage phones as well as
gateways, not to mention other capabilities.The CallManager is probably one of
the most intelligent parts of an IP telephony solution being that it has all the
knowledge of the network. A single CallManager can (with the correct hardware
configuration) support up to 2,500 extensions, allowing the organization to
expand seamlessly should the need arise. In a fully configured cluster, this number
rises to 10,000.These figures change, however, when looking at the IPCC since
the IPCC Agent Desktop (as well as some other applications) has additional
weighting that needs to be taken into consideration.Weights for specific devices
are discussed in Chapter 4, and should give you an idea of how many devices it’s
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possible to use on a specific CallManager in a non-IPCC solution.The following
are some design considerations when looking at the maximum amount of agents
supported in an IPCC:
Up to a maximum of 200 agents per CallManager
Maximum of 500 IPCC agents, regardless of the number of CallManagers
Maximum of 2.77 calls per second per CallManager (This equates
roughly to 10,000 Busy Hour Call Completions [BHCC].)
NOTE
At the time of this writing, the upper limit of supported agents was currently
enforced by Cisco. However, in the short- to medium-term, these
numbers will hopefully increase or even fall away so as to basically cater
to the majority of IPCC installations. When implementing an IPCC,
remember to ensure that all of the version numbers of the different
components (CallManager, IP-IVR, ICM, and so on ) are supported within
the IPCC solution. For more details on the current supported versions,
please refer to the following URL: www.cisco.com/warp/customer/78/
sw_compatability_matrix.html.
A single CallManager can be used in a call center environment as well as
being used in the traditional PBX type role. However, this should be done with
caution.This type of environment, while probably cost efficient, could lead to
disaster should there be any problems with the CallManager (for example, if
someone inadvertently switches off the power). Since CallManager 3.x, it has
been possible to have an IP phone register with multiple CallManagers.What this
means is that even if the primary CallManager was switched off, the IP phone
would still be able to operate via a secondary or even tertiary CallManager.With
applications such as the IP-IVR, IP SoftPhone, IP-Integrated Contact
Distribution (IP-ICD), and Personal Assistant, this was not possible. If the primary
CallManager were switched off for example, this would mean that the application
would not work.With the release of CallManager 3.1, this has changed.Within a
CallManager cluster, there is now the option to use the CTI Manager to provide
TAPI/JTAPI redundancy.This, in effect, means that if, for example, your Primary
CallManager were to be switched off, your application (if it is using TAPI/JTAPI)
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would be able to reconnect to another configured CallManager within a cluster.
Features such as that just described allow the CallManager to provide redundancy
and resiliency throughout a Cisco AVVID Network.