Cisco Unified CallManager System Guide, Release 5.0(1)
Cisco IP Telephony Overview
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Cisco IP Telephony Overview

Table Of Contents

Cisco IP Telephony Overview

Internet Ecosystem

Cisco IP Telephony Support


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 connect their disparate PBXs via their wide-area data network, to avoid long-distance charges.

Converging these previously disparate networks into a single, unified network realizes 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 IP Telephony Support

Cisco IP telephony support encompasses the following components:

Converged client devices


Directory services

Call processing

Telephony/data applications

Network management

Service and support

Cisco IP telephony 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 IP telephony support 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 includes the major Cisco IP Telephony voice and video applications:

Cisco CallManager—This software-only call-processing application distributes calls, features, phones, regions, and groups over an IP network.

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

Cisco Unity Connection. For more information about Cisco Unity Connection, refer to the Cisco CallManager 5.0 SCCP Integration Guide for Cisco Unity Connection 1.1 or the Cisco CallManager 5.0 SIP Trunk Integration Guide for Cisco Unity Connection 1.1.

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

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 IP telephony:

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 Video Phone 7985—supports SCCP

Cisco IP Phone 7970/7971—supports SCCP and SIP protocols

Cisco IP Phone 7960/7961—supports SCCP and SIP protocols

Cisco IP Phone 7940/7941—supports SCCP and SIP protocols

Cisco Wireless IP Phone 7920—supports SCCP

Cisco IP Phone 7912—supports SCCP and SIP protocols

Cisco IP Phone 7911—supports SCCP and SIP protocols

Cisco IP Phone 7910—supports SCCP

Cisco IP Phone 7905—supports SCCP and SIP protocol

Cisco IP Phone 7902—supports SCCP

Cisco IP Conference Station 7936

Cisco IP Conference Station 7935

Cisco IP Communicator

Cisco IP Phone Expansion Module 7914

Cisco also supports various third-party SIP phones. Contact your Cisco representative for more information.

Cisco IP Telephony Network

The Cisco IP Telephony network includes the following components:

Cisco CallManager

Cisco IP Phones

IOS platforms

Power Over Ethernet (POE) switches

Digital gateways and trunks

Analog gateways


Conferencing (hardware/software)

Media Termination Point (MTP)

Music On Hold (MOH)


Inline power modules (10/100 Ethernet switching modules)

Cisco IP Communicator

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

Introduction, page 1-1

System Configuration Overview, page 3-1

Device Support, page 11-1

Understanding Cisco CallManager Voice Gateways, page 39-1

Transcoders, page 25-1

Conference Bridges, page 24-1

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