The call processing agent layer is responsible for processing of calls (originating, routing, terminating calls etc) and related functionality such as device control, administration of dial plans and so on.  Whenever a call is made the function of call processing agent layer starts with generating a dial tone.  Ring signal is generated and call is connected to remote device.  While redialing, transferring, holding call the call processing agent gets activated.  The call processing layer functionality in Cisco is offered by a CallManager, due to its huge cost investments this solution does not offer cost effective functionality to small – medium size enterprises, so in order to cater the underline segments Cisco call processing portfolio is now coming with four different offerings:

  • Cisco Unified Communications 500; support for 48 users
  • Cisco Unified Communications Manager Express; support for 250 users
  • Cisco Unified Communication Manager Business Edition; support for 500 users
  • Cisco unified Communication Manager (CallManager): 30,000 + users

Before we go in details of each of the offerings, we first need to understand the functionality of a call processing manager in brief and that will give us better understanding of products operating at this layer from CCNA Voice exam perspective.  Call manager provides the following functionality in a UC environment:

  • Call processing:  Handling Call origination, routing, termination , billing etc.
  • Signaling and device control:  Setting up signaling connections (Call setup/call teardown) between endpoints and directs devices such as phones, gateways, and conference bridges to establish and tear down streaming connections.
  • Dial plan administration:  Call routing and digit analysis of all calls.
  • Phone feature administration:  Providing services such as hold, transfer, forward, conference, speed dial, redial, call park and so on to IP phones and gateways.
  • Directory services: Leverages users already configured in corporate-wide directory. Microsoft Active Directory (2000 and 2003), Netscape 4.x, iPlanet 5.1, and Sun ONE 5.2 directory integrations are supported. The local CUCM database is a Lightweight Directory Access Protocol (LDAP)-compliant database (LDAPv3) component in the IBM Informix Database Server (IDS).
  • Programming interface to external applications: Programming interface to external applications such as Cisco IP Soft Phone, Cisco IP Communicator, Cisco Unified IP Interactive Voice Response (IP IVR), Cisco Personal Assistant, Cisco Unified Personal Communicator, and CUCM Attendant Console.
  • Backup and restore tools: Provides Disaster Recovery System (DRS) to back up and restore the Call manager configuration database. Keeping backups of call details records (CDR), call management records (CMR) and the CDR Analysis and Reporting (CAR) database.


Cisco Unified Communications 500 Series – Is a perfect fit for small business requirements and a single box solution with many legacy systems PBX capabilities.  It eliminates the need for multiple servers and combines voice, data, video, security, and wireless capabilities.  Some of the key features of this device are outlined below:

  • Support for 8 to 104 IP phone stations
  • 4 to 12 analogue trucks or 2 to 8 Basic rate interface (BRI) digital trunks
  • Optional 1 or 2 T1/E1 voice interface
  • Integrated voicemail
  • Automated attendant
  • Integrated business applications to enhance productivity
  • Integrated security
  • Music on hold
  • Integrated wireless with selected models
  • Built-in VPN support (10 users) for secure access
  • Web based configuration and management interface

This is ideally suited for office environments where full time IT staff might not be available, as it is easy to manage and administer with a web based interface.

Cisco Unified Communications Manager Express – This device is scalable up to 250 IP phones, only dependency is the router platform chosen to run the communication manager express.


Number of IP Phones 

Cisco 1861 Integrated service router  


Cisco IAD2430 Integrated access device 


Cisco 2801 Integrated service router


Cisco 3250 Ruggedize service router


Cisco 3270 Ruggedize service router


Cisco 2811 integrated service router


Cisco 2821 integrated service router


Cisco 2851 integrated service router


Cisco 3725 multiservice access router


Cisco 3745 multiservice access router


Cisco 3825 integrated service router


Cisco 3845 integrated service router



Some additional features comes as add on for upgrading to Cisco Unified Communications Manager Express such as:

  • Integration with existing business process applications such as customer relationship management (CRM).
  • Users have Call controls, location and status of other users for Microsoft Windows.

Cisco Unity Express handles the voicemail for Cisco Unified Communications Manager Express which runs on a LINUX based platform installed on flash card/ hard drive. A single device which runs Cisco Unified Communications Manager Express and Cisco Unity Express on a fully Integrated Services Router (ISR) gives complete functionality for data and voice network.

Cisco Unified Communication Manager Business Edition – Cisco Unified Communications Manager Business Edition contains voice, messaging, mobility, and video capabilities integrated as an all in one system on a single server.  It runs on a LINUX based platform and gives scalability to support 500 employees and 20 sites. T his server comprises of three core components:

  • Cisco Unified Communication Manager with integrated mobility features.
  • Cisco Unity Connection.
  • Cisco MCS 7828 Media Convergence Server.

The software preloaded on the server consists of a single firmware image that includes the OS as well as call processing and messaging applications.  In addition to standard call processing features it also provides features that improve the productivity of mobile employees including Cisco Unified Mobility which provides a single business voice mailbox and a single number search capability which intelligently does management of filters, routes, and places calls between a worker’s IP phone and remote mobile phone.

Cisco Unity Connection is the messaging components which integrates messaging and voice recognition function to provide global access to calls and messages.

Media Convergence Servers provide the platform to run Cisco Unified Communication Manager; it is a rack mountable server with single SATA hard drive and single power supply. The 7800 series servers are available only in two variants H and I. where H stands for Hewlett-Packard and I for IBM. The server reliability can be improved by adding hot swappable SCSI drives, RAID 1 disk duplexing and redundant power supply.

Cisco Unified Communication Manager (CallManager) – For ultimate redundancy and scalability look for this device.  It is scalable to virtually any size and implements redundant servers that can support IP phones and applications in the event of failure of a primary call processing server.

To summarize table given below gives a comparison of all call processing products.


Number of users

Redundancy support

Server/router based

Cisco UC500

8 to 48



Cisco unified communication manager express

Up to 250



Cisco unified communication manager business edition

Up to 500



Cisco unified communication manager

30,000 per cluster




In this lesson we have covered in details of Call Processing Manager and its different flavors.  Along with this it concludes the role and function of Call Processing Layer in Unified Communication. In the next CCNA Voice topic, we will learn about other layers of Cisco voice communication layer.