Information Technology Reference
In-Depth Information
integrates with Survivable Remote Site Telephony (SRST), which allows the CME
router to act as a backup to a primary call-management system (perhaps CUCM).
Standards-based:
All signaling between the CME router and CUE module use the
SIP protocol, which is becoming the universal standard for voice signaling.
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When Cisco first released CallManager 2.4, it ran as an application on the Microsoft Win-
dows NT 4.0 OS supported by the Internet Information Server (IIS) web server. You could
even install it on a laptop to give yourself a battery backup power supply in case of a
power outage.
Note:
Cisco does not recommend installing CallManager on a laptop to give yourself a
battery backup power supply.
Needless to say, Cisco has come a long way as CUCM moves through the 8.X versions and
beyond. It now runs as a Linux appliance on certified hardware platforms and acts as the
powerful call processing component of the Cisco Unified Communications solution. Think
of CUCM as the “director” behind any large organization's Cisco IPT solution. It provides
the core device control, call routing, permissions, features, and connectivity to outside ap-
plications. The scope of control handled by CUCM is so large, Cisco created two certifica-
tion exams for it in the CCNP Voice certification track (CIPT1 and CIPT2). In a nutshell,
the importance of CUCM to Cisco VoIP is monumental. With that being said, don't the
massive size of CUCM to overwhelm you. Cisco has done a fantastic job at allowing you to
manage nearly every CUCM option through a crisp, well-designed web-based GUI.
CUCM Key Features
Although CUCM supports numerous capabilities, here are some of the most important:
Key
To p i c
Full support for audio and video telephony:
The core feature provided by
CUCM. In the same way CME acts as the director of a small organization, CUCM
supports audio and video calls for midsize to enterprise class corporations.
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Appliance-based operation:
Modern CUCM versions run as an appliance, which
means the underlying operating system is hardened (secured) and inaccessible.
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Redundant server cluster:
As the saying goes, “One is none, two is one.” CUCM
supports redundant servers configured in a cluster relationship. The clustering capa-
bilities replicate both database information (containing static data such as directory
numbers and route plans) and real-time information (containing dynamic data, such as
active calls). CUCM clusters can scale to 30,000 IP phones (SCCP or SIP in unsecure
mode) or 27,000 IP phones (SCCP or SIP in secure mode).
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Intercluster and voice gateway control and communication:
Even though a
CUCM cluster has a limit of 30,000 IP phones, you can create as many clusters as you
like (with up to 30,000 IP phones each) and connect them together using intercluster
trunk connections. In addition to using Intercluster trunk links to call outside of your
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