Expert Reference Series of White Papers
Cisco Unified
Communications
Manager Express
1-800-COURSESwww.globalknowledge.com
Cisco Unified Communications
Manager Express
Joe Rinehart, MBA, CCIE #14256, CCNP/DP/VP
Introduction
Figure 1: Cisco Unified Communications 520 Appliance
www.cisco.com
Cisco Systems’ initial claim to fame involved the development of a multiprotocol routing device (usually simply referred to as a router) that performed various tasks and features in software. Since those early days, the
company has maintained and expanded the original equipment platform, as well as ventured into other technological areas. To expand product and service offerings, Cisco typically will target a company in a specific area of
expertise and then acquire that entity, including products, software, and personnel. Such was the case with the
addition of VoIP—voice telephony—to the Cisco family, when the company acquired Selsius Systems in 1998.
The platform was predictably named Selsius Call Manager, which became Cisco Call Manager for several years,
before being renamed once again as the Cisco Unified Communications Manager (CUCM). In order to adapt the
technology for all sizes of businesses, two distinct products were created. The first of these, Cisco Call Manager/
Unified Communications Manager (CUCM), is server-based and targeted at larger organizations. The second,
Cisco Call Manager/Unified Communications Manager Express (CUCME), was sized for the small-to-mediumsized business (SMB) space. This white paper will concentrate on the CUCME platform, which operates in a
significantly different manner than its larger counterpart.
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Hardware-Based Call Control
Figure 2: CUCME Logical Layout/Icons
When approaching the subject of the CUCME, the obvious distinction of this product is that it is hardwarebased, typically a router (see Figure 2 above). The software feature set was originally named IP Keyswitch as far
back as IOS 12.1(5), and later renamed IOS Telephony Services. Supported platforms included the older 2600
and 3600 router models, as well as some integrated access devices. Later versions utilized the more current
naming conventions of Cisco Call Manager Express/Communications Manager Express, and still are supported
on various router models, as well as specialized devices, such as the UC 520 (see Figure 1). In early releases of
this router-based call control platform, most of the configuration for telephony features took place at the command line, though graphical user interface (GUI) options were added later. In many ways, the CUCME platform
has many more limitations and a narrower set of features than the full-fledged CUCM. Certain benefits come,
however, from the lower cost and smaller footprint, in which the device acts almost as an “all in one” type
appliance.
Onboard PSTN Termination
In a CUCM deployment, a specialized router with telephony interfaces performs the process of sending and
receiving traditional voice calls, usually referred to as a Voice Gateway. In a CUCME setting, the device performing the call processing is also doing this conversion process. Typically, the telephony interfaces in the gateway
include the following:
• Foreign Exchange Station/FXS: Standard analog telephony devices such as handsets or FAX
machines
• Foreign Exchange Office/FXO: Standard analog line connecting to the Central Office (incoming/
outgoing calls)
• T1/E1: Digital telephony interface that processes multiple calls simultaneously, up to 24 channels/conversations
• Session Initiation Protocol (SIP) Trunk: A more recent, network-based call control protocol and
connection that sends calls over a network rather than using traditional telephony interfaces
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In addition to the use of analog and digital telephony interfaces, the gateway uses a series of special-purposes
conversion chips called digital signal processors (DSPs) to convert to/from network-based VoIP calls and traditional public switched telephone network (PSTN) calls. Again, in CUCME, all of these processes take place on a
single device that performs all necessary tasks.
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ging
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inging
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Figure 3: CUCME Call Setup
Call Control and Signaling
All VoIP-based calling involves the use of specific protocols that emulate the various processes used by traditional telephony environments, described as signaling. Signaling protocols supply dial tone to an IP handset,
gather the digits to identify a called party, and perform the necessary lookups and initiation of the call setup
process. As shown in Figure 3, call signaling traffic flows between the handset and the CUCME device. Keep in
mind that what is depicted here is handset-to-handset traffic; there would be an additional outbound process
between the CUCM device and the PSTN. Each of these is referred to as a “call leg” and represents a distinct
segment of the entire voice call process. Signaling protocols include older H.323 signaling (also used with
video); SCCP/”Skinny” (proprietary, used on Cisco IP phones); and session initiation protocol (SIP), an open standard that has gained much wider acceptance. Bearer traffic is carried by the real-time transport protocol (RTP)
and flows directly between endpoints. If the call were designated to the PSTN, the RTP stream would exist only
between the handset and the gateway, and that device would convert to/from the PSTN.
Registration
If you have ever had to move from an old residence to a new one, then you probably have first-hand experience
with moving traditional phone services. This does not happen automatically, where the analog phone from the
old location simply has dial tone and service at the new residence. This requires intervention by the service provider and sometimes an on-site visit by a technician. In the CUCME world, a similar process called registration
performs all of these tasks, in which the handset is discovered, recoded in the system, and allocated service,
based on configured settings. The beauty of this process is that the user can move from one part of the facility/
home to the other, plug the phone into the network, and it instantly gets reconfigured with identical settings.
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Feature Support
What CUCME CAN do
By design, CUCME supports a smaller number of users at a reduced price point, which naturally translates into a
reduced number of features when compared to CUCM. Even so, this deployment model can perform a
respectable set of features used in smaller office settings. This includes music on hold, conferencing, hunt
groups, limited call-center features, intercom, PSTN calling, voice messaging (with additional modules/software),
call waiting, and caller-id, to name a few.
What CUCME CANNOT do
CUCME cannot fit every possible need, especially for larger organizations, though it can serve an initial role
as a business grows. In most cases, then, the router can continue to act as a voice gateway with a full-fledged
CUCM system, preserving investment costs. Certain router platforms have limitations on the number of handsets
that they can support; this is not so much a licensing issue as it is a resource issue. On the largest of the router
platforms, 450 IP phones is the limit and cannot scale above that. CUCME also can have problems with multiple
locations if a single unified dial plan is desired. In these cases, a separate CUCME device can be deployed at
each site, with entries for direct dialing. In addition, although CUCME can support a simple, basic call center, it is
not designed to support sophisticated call routing capabilities.
Conclusion
Unified Communications, once a cutting-edge approach to voice communications, has gained status as a widely
adopted way of communicating. Leveraging a more integrated approach between data networks and voice
communications, this technology brings an incredible feature set to even smaller business entities. For smaller
companies, the Cisco Communications Manager Express, or CUCME, can enable business-class telephony with
lower operational costs.
Learn More
To learn more about how you can improve productivity, enhance efficiency, and sharpen your competitive edge,
Global Knowledge suggests the following courses:
ACUCMX - Administering Cisco Unified Communications Manager and Unity
CVOICE - Implementing Cisco Unified Communications Voice over IP and QoS v8.0
Visit www.globalknowledge.com or call 1-800-COURSES (1-800-268-7737) to speak with a Global
Knowledge training advisor.
About the Author
Joe Rinehart, MBA, CCIE #14256, CCNP/DP/VP is a professional trainer specializing in technology, business, and
social media. He is also a successful speaker and published author, as well as a columnist for the Federal Way
Mirror. He is active in the social media space, managing one of the largest groups on LinkedIn, as well as serving
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on the national steering committee of the Cisco Collaboration Users Group. Joe also served as president of the
Seattle Cisco Users Group, serving technology professionals throughout the Puget Sound region.
Joe Rinehart
MBA, CCIE #14256, CCNP/DP/VP
President and Chief Edutainment Officer
Gracestone Professionals, LLC
jrinehart@gracestonecompany.com
Twitter: jjrinehart
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