So far we have learned about functions of infrastructure and endpoint layers and also learned about devices that operate at these layers.  Applications are independent of call control functions and physical layer voice processing infrastructure; they can reside anywhere within the network and integrated through IP.  One such popular and most commonly used application is voice mail, integrated messaging and unified messaging applications.  Cisco Unity product line deals with messaging requirements.  Traditional phone systems deliver messages only to telephonic devices, whereas with Cisco Unity we can deliver messages to a variety of clients such as fax messages, voice mail, email all can be delivered to a single mailbox.

The Cisco Unity products line has three variations/flavors.  We will learn about each of them in detail in subsequent sections.

Cisco Unity Express (CUE) – Cisco Unity express is available as network module or advanced integration module to Cisco 1861, 2800, 2900, 3800 and 3900 series routers.  It can be embedded as flash module or hard drive to Cisco router.  Flash module version is plugged in as Advanced Integration Module (AIM) to the motherboard router, and the hard drive version is installed as a network module.  If you are looking for limited storage for voice mails and automated attendant recordings or scripts then you can go for a flash module, for vast storage requirements network module is a more suitable choice.  Cisco Unity Express boots as LINUX based application in order to keep voice email functions separately from router function.  It also offers limited IVR capabilities such as transfer calls to different lines assigned to departments such as sales, projects, finance etc. Some of the major features of Cisco Unity Express are as under:

  • It is scalable up to 24 concurrent voicemail or autoattendent calls and 275 mailboxes
  • View, sort, search, and play back voice messages using Cisco IP phone or email client
  • Web based interface for voicemail, autoattendent, and interactive voice administration
  • Time card data management
  • Voice messaging and greeting services

Cisco Unity Connection – Combines/integrates voice mail and email features of Cisco Unity Express with some advanced functionalities and support for user base more than 100 and up to 7500 users.   Advanced call routing features like routing based on time of day, caller ID, speech recognition and so on) are supported. For less than 500 users Cisco Unity Connection can be combined in a single server solution along with Cisco Unified Communication Manager, Business Edition. For user a base of more than 500 users, a dedicated Cisco Unity Connection can be added on a separate server to scale up to 7500 users.  Some of the major features of Cisco Unity Connection are described below:

  • Speech attendant for numberless enterprise.
  • Speech connect facility support all employees in a directory irrespective of they are using unity connection or not.
  • Dial tone replacement with “text based response”.

Cisco Unity – If you are looking for a dedicated messaging solution for VOIP networks with a support for a larger user base Cisco Unity is the right choice.  It can support 7500 users per server and additional servers can be added to support more than 25,000 users.  This system can be integrated with other popular messaging solutions and legacy voicemail systems such as Microsoft Exchange, Lotus Notes, and Novell GroupWise and so on.  Some of the major features of Cisco Unity are noted below.

An integrated messaging platform that lets you access email, voice and fax messages from a single mailbox anytime, anywhere, it is a also supported on virtual platforms like VMWare.

It can be integrated with other email system thus enabling users to forward voice messages as email attachments to any other messaging platform email users such as exchange, Lotus notes, GroupWise etc.

  • Voice messages can be left for multiple recipients with a single call.
  • Users can listen there voice mail messages from a telephone.
  • Responding to email message over phone with audio content.
  • Faxes can be stored as TIF files in email client/disk.
  • Can be integrated to legacy PBX systems.

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


Number of users 

Redundancy support 

Email support 

Server / router based

Cisco Unity Express

Up to 250


Voicemail relay to external email server


Cisco Unity Connection

Up to 7500


Voicemail relay to external email server


Cisco Unity

Up to 7500 per server, network to 250,000



Integrates with other messaging platforms such as Exchange, Lotus Notes, GroupWise



This concludes the function of applications, in this lesson particularly we have learned about messaging functionality on VOIP networks.  For our CCNA Voice exam readers, this lesson will help them to understand how messaging works in a converged voice network and how Cisco messaging products integrate with other messaging platforms. In the next CCNA Voice topic, we will learn about other applications such as IVRs, auto attendants, contact centers etc.