© 2006 Cisco Systems, Inc. All rights reserved.

Optimizing Converged Cisco Networks (ONT)

Module 2: Cisco VoIP Implementations

© 2006 Cisco Systems, Inc. All rights reserved.

Lesson 2.5: Implementing VoIP in an Enterprise Network

© 2006 Cisco Systems, Inc. All rights reserved.

Objectives List the common components of an enterprise voice

implementation.

Describe Call Admission Control and how it differs from QoS.

Describe the functions of the Cisco Unified CallManager.

Identify common enterprise IP telephony deployment models.

Identify basic Cisco IOS VoIP configuration commands.

© 2006 Cisco Systems, Inc. All rights reserved.

Enterprise Voice Implementations Components of enterprise voice networks:

Gateways and gatekeepers

Cisco Unified CallManager and IP phones

© 2006 Cisco Systems, Inc. All rights reserved.

Deploying CAC CAC artificially limits the number of concurrent voice calls.

CAC prevents oversubscription of WAN resources caused by too much voice traffic.

CAC is needed because QoS cannot solve the problem of voice call oversubscription:

QoS gives priority only to certain packet types (RTP versus data).

QoS cannot block the setup of too many voice calls.

Too much voice traffic results in delayed voice packets.

© 2006 Cisco Systems, Inc. All rights reserved.

Example: CAC Deployment

IP network (WAN) is only designed for two concurrent voice calls.

If CAC is not deployed, a third call can be set up, causing poor quality for all calls.

When CAC is deployed, the third call is blocked.

© 2006 Cisco Systems, Inc. All rights reserved.

Voice Gateway Functions on a Cisco Router

Connects traditional telephony devices to VoIP

Converts analog signals to digital format

Encapsulates voice into IP packets

Performs voice compression

Provides DSP resources for conferencing and transcoding

Supports fallback scenarios for IP phones (Cisco SRST)

Acts as a call agent for IP phones (Cisco Unified CallManager Express)

Provides DTMF relay and fax and modem support

© 2006 Cisco Systems, Inc. All rights reserved.

Cisco Unified CallManager Functions

Call processing

Dial plan administration

Signaling and device control

Phone feature administration

Directory and XML services

Programming interface to external applications Cisco IP Communicator

© 2006 Cisco Systems, Inc. All rights reserved.

Example: Signaling and Call Processing

© 2006 Cisco Systems, Inc. All rights reserved.

Enterprise IP Telephony Deployment Models

Deployment Model Characteristics

Single site – Cisco Unified CallManager cluster at the single site

– Local IP phones only

Multisite with centralized call processing

– Cisco Unified CallManager cluster only at a single site

– Local and remote IP phones

Multisite with distributed call processing

– Cisco Unified CallManager clusters at multiple sites

– Local IP phones only

Clustering over WAN – Single Cisco Unified CallManager cluster distributed over multiple sites

– Usually local IP phones only

– Requirement: Round-trip delay between any pair of servers not to exceed 40 ms

© 2006 Cisco Systems, Inc. All rights reserved.

Single Site Cisco Unified CallManager

servers, applications, and DSP resources are located at the same physical location.

IP WAN is not used for voice.

PSTN is used for all external calls.

Note: Cisco Unified CallManager cluster can be connected to various places depending on the topology.

© 2006 Cisco Systems, Inc. All rights reserved.

Multisite with Centralized Call Processing

Cisco Unified CallManager servers and applications are located at the central site while DSP resources are distributed.

IP WAN carries data and voice (signaling for all calls, media only for intersite calls). PSTN access is provided at all sites. CAC is used to limit the number of VoIP calls, and AAR is used if WAN bandwidth

is exceeded. Cisco SRST is located at the remote branch.

Note: Cisco Unified CallManager cluster can be connected to various places depending on the topology.

© 2006 Cisco Systems, Inc. All rights reserved.

Multisite with Distributed Call Processing

Cisco Unified CallManager servers, applications, and DSP resources are located at each site.

IP WAN carries data and voice for intersite calls only (signaling and media). PSTN access is provided at all sites; rerouting to PSTN is configured if IP WAN is

down. CAC is used to limit the number of VoIP calls, and AAR is used if WAN bandwidth

is exceeded.Note: Cisco Unified CallManager cluster can be connected to various places, depending on the topology.

© 2006 Cisco Systems, Inc. All rights reserved.

Clustering over WAN

Cisco Unified CallManager servers of a single cluster are distributed among multiple sites while applications and DSP resources are located at each site.

Intracluster communication (such as database synchronization) is performed over the WAN.

IP WAN carries data and voice for intersite calls only (signaling and media). PSTN access is provided at all sites; rerouting to PSTN is performed if IP WAN is down. CAC is used to limit the number of VoIP calls; AAR is used if WAN bandwidth is exceeded.

Note: Cisco Unified CallManager cluster can be connected to various places, depending on the topology.

© 2006 Cisco Systems, Inc. All rights reserved.

Basic Cisco IOS VoIP Voice Commands

© 2006 Cisco Systems, Inc. All rights reserved.

Voice-Specific Commands

dial-peer voice tag type

router(config)#

Use the dial-peer voice command to enter the dial peer subconfiguration mode.

destination-pattern telephone_number

router(config-dial-peer)#

The destination-pattern command, entered in dial peer subconfiguration mode, defines the telephone number that applies to the dial peer.

© 2006 Cisco Systems, Inc. All rights reserved.

Voice-Specific Commands (Cont.)

router(config-dial-peer)#

session target ipv4:ip-address The session target command, entered in VoIP dial peer subconfiguration mode,

defines the IP address of the target VoIP device that applies to the dial peer.

port port-number The port command, entered in POTS dial peer subconfiguration mode, defines the

port number that applies to the dial peer. Calls that are routed using this dial peer are sent to the specified port.

router(config-dial-peer)#

© 2006 Cisco Systems, Inc. All rights reserved.

Self Check

1. What is CAC?

2. What can happen is CAC is not used?

3. What command is used to define the telephone number that applies to the dial peer?

4. List 4 deployment options when using the Cisco Unified CallManager.

© 2006 Cisco Systems, Inc. All rights reserved.

Summary Enterprise voice implementations use components such

as gateways, gatekeepers, Cisco Unified CallManager, and IP phones.

Call Admission Control (CAC) extends the functionality of QoS to ensure that an additional call is not allowed unless bandwidth is available to support it.

Enterprise IP Telephony deployment models include single site, multisite with centralized call processing, multisite with distributed call processing, and clustering over the WAN.

© 2006 Cisco Systems, Inc. All rights reserved.

Q and A

© 2006 Cisco Systems, Inc. All rights reserved.

Resources Video: The ABCs of VoIP (16 min.)

http://tools.cisco.com/cmn/jsp/index.jsp?id=43596

Voice and Unified Communicationshttp://www.cisco.com/en/US/products/sw/voicesw/index.html

VoIP Call Admission Controlhttp://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/voipsol/cac.htm

© 2006 Cisco Systems, Inc. All rights reserved.