Cisco CallManager System Guide, Release 4.1(3)
Cisco IP Telephony Overview

Table Of Contents

Cisco IP Telephony Overview

Internet Ecosystem

Cisco Architecture for Voice, Video, and Integrated Data (Cisco AVVID)


Call Processing



Cisco IP Telephony Network

Where to Find More Information

Cisco IP Telephony Overview

Multiple communication networks exist as entirely separate entities, each serving a specific application. The traditional public switched telephone network (PSTN) time-division multiplexing (TDM) network serves the voice application; the Internet and intranets serve data communications.

Business requirements often force these networks to interoperate. As a result, deploying multiservice (data, voice, and video) applications such as unified messaging or web-based customer contact centers requires expensive and complex links between proprietary systems, such as private branch exchanges (PBXs) and standards-based data networks.

The traditional enterprise communication takes place on two separate networks:



Internet Ecosystem

Over time, the Internet (and data networking technology in general) encompassed the traditional traffic types. This convergence recently started to absorb voice and video as applications into the data network. Several large Post, Telephone, and Telegraph (PTT) carriers use packet switching or voice over ATM as their backbone technology, and enterprise customers accept virtual trunking, or connecting their disparate PBXs via their wide-area data network, to avoid long-distance charges.

By converging these previously disparate networks into a single, unified network, you can begin to realize savings in multiple areas, including lower total cost of ownership, toll savings, and increased productivity.

Cisco CallManager and Cisco IP Phones provide an IP telephony solution that operates on an IP infrastructure. The clustering architecture of Cisco CallManagers allows you to scale to a highly available voice-over-IP (VoIP) network.

Cisco Architecture for Voice, Video, and Integrated Data (Cisco AVVID)

Cisco AVVID encompasses the following components:

Converged client devices


Directory services

Call processing

Telephony/data applications

Network management

Service and support

Cisco AVVID solutions enable you to

Deploy IP-enabled business applications

Implement a standards-based open architecture

Migrate to a converged network in your own time frame

Cisco AVVID enables you to move from maintaining a separate data network and a closed, proprietary voice PBX system to maintaining one open and standards-based, converged network for all your data, voice, and video needs.


The following list gives some voice and video applications in the application layer of Cisco AVVID:

Cisco Unity—The Cisco Unity messaging application provides voice messaging to enterprise communications.

Video—IP-TV and IP-video conferencing products enable distance learning and workgroup collaboration.

Cisco IP IVR—As an IP-powered interactive voice response (IVR) solution, Cisco IP IVR, combined with Cisco IP AutoAttendant, provides an open and feature-rich foundation for delivering IVR solutions over an IP network.

Cisco CallManager Attendant Console—This flexible and scalable application replaces the traditional PBX manual attendant console.

Cisco IP SoftPhone—The Cisco IP SoftPhone, a software, computer-based phone, provides communication capabilities that increase efficiency and promote collaboration.

Cisco Personal Assistant—Cisco Personal Assistant selectively handles calls and helps you make outgoing calls. Cisco Personal Assistant provides rule-based call routing, speech-enabled directory dialing, voice message browsing, and simple ad hoc conferencing.

Call Processing

Cisco CallManager, a software-only call-processing application, distributes calls and features and clusters phones, regions, and groups over an IP network, which allows scalability to 30,000 users and triple call-processing redundancy.

Cisco CallManager provides signaling and call-control services to Cisco-integrated applications, as well as to third-party applications.


The following list shows the components of the infrastructure layer of Cisco AVVID:

Media convergence servers

General voice products for Cisco IP Telephony Solutions


Integrated IP telephony solution

Voice trunks

Voice gateways

Toll bypass products

IP protocols such as MGCP, H.323, and SIP


Cisco delivers the following IP-enabled communication devices:

Cisco IP Phone 7970

Cisco IP Phone 7960

Cisco IP Phone 7940

Cisco IP Phone 7912

Cisco IP Phone 7910

Cisco IP Phone 7905

Cisco IP Phone 7902

Cisco IP Conference Station 7936

Cisco IP Conference Station 7935

Cisco IP SoftPhone

Cisco IP Phone Expansion Module 7914

Cisco IP Telephony Network

The Cisco IP Telephony network includes the following components:

Cisco CallManager

Cisco IP Phones

IOS platforms

Digital gateways

Analog gateways


Conferencing (hardware/software)

Media Termination Point (MTP)

Music On Hold (MOH)


Inline power modules (10/100 Ethernet switching modules)

Cisco IP SoftPhone

Control from the Cisco IP Phone to Cisco CallManager uses skinny client control protocol and, independently, desktop computer to Cisco CallManager, as an H.323 gatekeeper that is using H.225/H.245 over transmission control protocol (TCP).

Where to Find More Information

Related Topics


System Configuration Overview, page 3-1

Device Support, page 10-1

Understanding Cisco CallManager Voice Gateways, page 36-1

Transcoders, page 22-1

Conference Bridges, page 21-1

Additional Cisco Documentation

Cisco CallManager Configuration, Cisco CallManager Administration Guide

Device Defaults Configuration, Cisco CallManager Administration Guide

Cisco IP Phone Configuration, Cisco CallManager Administration Guide

Gateway Configuration, Cisco CallManager Administration Guide

Transcoder Configuration, Cisco CallManager Administration Guide

Conference Bridge Configuration, Cisco CallManager Administration Guide

Cisco CallManager Features and Services Guide

Cisco IP Telephony Solution Reference Network Design Guide

Cisco IP Phone user and administration documentation

Gateway documentation