Cisco voice over IP CVOICE student guide v4 2 PDF

Upon completing this course, you will be able to meet these objectives: Describe the similarities and differences between traditional PSTN voice networks and IP telephony solutions Expla

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CVOICE

Cisco Voice Over IP

Version 4.2

Student Guide

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(0203R)

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Understanding Packetized Telephony Networks 1-25

Understanding IP Telephony Applications 1-41

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Analog and Digital Voice Connections 2-1

Types of Trunk Signaling 2-17

E & M Signaling Types 2-21 Trunk Signal Types and Used by E & M 2-26

Undetstanding Analog-to-Digital Voice Encoding 2-43

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Compresson Bandwidth Requiremens 2-58 Voice Quality Measurement 2-59

Understanding Signaling Systems 2-67

Understanding Fax and Modem over VoIP 2-93

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Voice Port Applications 3-5

Echo Cancellation Commands 3-49

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Configuring Destination-Pattern Options 4-25

Matching Inbound Dial Peers 4-30 Matching Outbound Dial Peers 4-33

Understanding Special-Purpose Connections 4-61

Configuring Trunk Connections 4-67

Building a Scalable Numbering Plan 4-75

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Packet Loss, Delay, and Jitter 5-7

Understanding Gateways and Their Roles 5-21

Central and Remote Site 5-26 Determining Gateway Interconnection Requirements in a Service Provider

Encapsulating Voice in IP Packets 5-35

Calculating Bandwidth Requirements 5-51

Impact of Voice Samples and Packet Size on Bandwidth 5-55

Security and Tunneling Overhead 5-57 Specialized Encapsulations 5-58 Calculating the Total Bandwidth for a VoIP Call 5-59 Effects of VAD on Bandwidth 5-60

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Understanding Security Implications 5-67

Translation Between Signaling and Call Control Models 6-8

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H.323 Call Establishment and Maintenance 6-42 Call Flows Without a Gatekeeper 6-45 Call Flows with a Gatekeeper 6-48 Multipoint Conferences 6-50 Call Flows with Multiple Gatekeepers 6-52 Survivability Strategies 6-54

Cisco Implementation of H.323 6-58 Configuring H.323 Gateways 6-59 Configuring H.323 Gatekeepers 6-62 Monitoring and Troubleshooting 6-64

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Survivability Strategies 6-129 Cisco Implementation of MGCP 6-131 Understanding Basics of Cisco CallManager 6-132

Comparing Call Control Models 6-151

Improving and Maintaining Voice Quality 7-1

Understanding VoIP Challenges 7-17

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Understanding QoS and Good Design 7-37

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Verifying End-to-End Delay 7-84

Applying QoS in the Campus 7-91

Understanding QoS Tools in the WAN 7-111

Configuring QoS in the WAN 7-133

CiscoWorks QPM for QoS 7-152

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Effects of Oversubscribing Bandwidth on Overall Voice Quality 7-164 CAC as Part of Call Control Services 7-165

Understanding Voice Bandwidth Engineering 7-195

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Computer Telephony Integration 14 Collaborative Computing 16 Voice-Enabled Web Applications 17

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Course Goal and Objectives

This section describes the course goal and objectives

Course Goal

To provide an understanding

of converged voice and data networks as well as the

challenges faced by their various technologies

Cisco Voice over IP (CVOICE) v4.2

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Upon completing this course, you will be able to meet these objectives:

Describe the similarities and differences between traditional PSTN voice networks and IP telephony solutions

Explain the processes and standards for voice digitization, compression, digital signaling, and fax transport as they relate to VoIP networks

Configure voice interfaces on Cisco voice-enabled equipment for connection to traditional, nonpacketized telephony equipment

Configure the call flows for POTS, VoIP, and default dial peers Describe the fundamentals of VoIP and identify challenges and solutions regarding its implementation

Compare centralized and decentralized call control and signaling protocols Describe specific voice quality issues and the QoS solutions used to solve them

Course Outline

The outline lists the modules included in this course

Course Outline

Introduction to Packet Voice Technologies

Analog and Digital Voice Connections

Configuring Voice Interfaces

Voice Dial Plans

Introduction to VoIP

VoIP Signaling and Call Control

Improving and Maintaining Voice Quality

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Cisco Certifications

This topic lists the certification requirements of this course

Cisco provides three levels of general career certifications for IT professionals with several different tracks to meet individual needs Cisco also provides a variety of Cisco Qualified Specialist (CQS) certifications, which enable learners to demonstrate knowledge in specific technologies, solutions, or job roles In contrast to general certifications, each CQS certification

is focused on a designated area such as cable communications, voice, or security All CQS certifications are customized to meet current market needs They may also have special focused prerequisite requirements

There are many paths to Cisco certification, but only one requirementpassing one or more exams demonstrating knowledge and skill For details, go to

http://www.cisco.com/go/certifications

Course Certifications

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Learner Skills and Knowledge

This topic lists the course prerequisites

To benefit fully from this course, you must have these prerequisite skills and knowledge:

A working knowledge of LANs, WANs, and IP switching and routing Basic internetworking skills taught in the Interconnecting Cisco Network Devices (ICND)course, or its equivalent

Knowledge of traditional public switched telephone network (PSTN) operations and voice fundamentals

Prerequisite Learner Skills and Knowledge

WANS Basic Telephony Fundamentals

IP Switching Basic Internetworking Skills PSTN Operations and Technologies

CVOICE LANS

PBX Essentials

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Learner Responsibilities

This topic discusses the responsibilities of the learners

To take full advantage of the information that is presented in this course, you must have

completed the prerequisite requirements

In class, you are expected to participate in all lesson exercises and assessments

In addition, you are encouraged to ask any questions that are relevant to the course materials

If you have pertinent information or questions concerning future Cisco product releases and product features, please discuss these topics during breaks or after class The instructor will answer your questions or direct you to an appropriate information source

Learner Responsibilities

Completeprerequisites

Introduceyourself

Ask questions

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General Administration

This topic lists the administrative issues for the course

The instructor will discuss these administrative issues:

Sign-in process Starting and anticipated ending times of each class day Class breaks and lunch facilities

Appropriate attire during class Materials that you can expect to receive during class What to do in the event of an emergency

Location of the rest rooms How to send and receive telephone and fax messages

locations

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Course Flow Diagram

This topic covers the suggested flow of the course materials

Course Flow Diagram

Course Introduction

Lunch

Configuring Voice Interfaces

Improving and Maintaining Voice Quality

A

M

PM

Introduction

to VoIP (Cont.)

Voice Dial Plans

Analog and Digital Voice Connections

Configuring Voice Interfaces (Cont.) Introductionto VoIP

VoIP Signaling and Call Control (Cont.)

Intro to Packet Voice Technologies

VoIP Signaling and Call Control

Improving and Maintaining Voice Quality (Cont.)

Analog and Digital Voice Connections (Cont.) Voice Dial Plans

(Cont.)

VoIP Signaling and Call Control (Cont.)

The schedule reflects the recommended structure for this course This structure allows enough time for the instructor to present the course information and for you to work through the laboratory exercises The exact timing of the subject materials and labs depends on the pace of your specific class

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Icons and Symbols

This topic shows the Cisco icons and symbols used in this course

Cisco Icons and Symbols (Cont.)

Voice-Enabled ATM Switch

Voice-Enabled Communications Server

Multilayer Switch, With and Without Text and Subdued

Si Si

SC2200 Signaling Controller

Web Cluster

Camera PC/Video

PBX/

Switch

Data Center Switch, Reversed

Web Browser

Server

Cisco Icons and Symbols

Enabled Router

Voice-PBX (Small)

Network Cloud, Standard Color

Network Cloud, White

Phone

IP Phone

Phone 2

Generic Softswitch

Cisco PIX Firewall Right and Left

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Learner Introductions

This is the point in the course where you introduce yourself

Prepare to share the following information:

Your name Your company

If you have most or all of the prerequisite skills

A profile of your experience What you would like to learn from this course

Learner Introductions

Your name

Your company

Skills and knowledge

Brief history

Objective

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Migration is a process that involves gradually phasing out old components and replacing them with new ones Many terms have been used to describe the technologies and applications for transporting voice in a converged packet network environment When designing a converged network, it is necessary to clearly define all requirements and understand the various options that are available

An important first step in designing a converged network is to understand the traditional telephony network and how it interfaces with voice components You must know, from the start, how legacy voice equipment is connected and its possible migration paths

The next step toward a good design is being knowledgeable about the components available for Packet Telephony Networks You should be aware of the difference between voice and data flow within the network and the tools for controlling voice calls Network requirements vary according to the location size Knowing the difference between campus, enterprise, and service provider environments is crucial in choosing the right components and technologies

This module provides an overview of the basic telephony functions and devices, including PBXs, switching functions, call signaling, and multiplexing techniques It also reviews the basic components of the Packet Telephony Network and identifies the different requirements in campus, enterprise, and service provider environments Together, these concepts and

techniques provide a solid introduction to the VoIP arena

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Identify the components, processes, and features

of traditional telephony networks that provide end-to-end call functionality

Describe two methods of call control used on voice and data networks and provide one protocol example for each

List five components or capabilities that are required to provide integrated voice and data services in campus LAN, enterprise, and service provider environments

Module Outline

The outline lists the components of this module

Module Outline

Understanding Traditional Telephony

Understanding Packetized Telephony Networks

Understanding IP Telephony Applications

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be supported and the processes that are necessary to ensure end-to-end call functionality

Objectives

Upon completing this lesson, you will be able to identify the components, processes, and features of traditional telephony networks that provide end-to-end call functionality This includes being able to meet these objectives:

Describe the components and functionality of traditional telephony networks Explain how CO switches process telephone calls

Identify types of private switching systems used in traditional telephony networks and list the main features of each

Describe the three types of signaling in traditional telephony networks and identify how each is used

Describe two methods used to multiplex voice in traditional telephony networks

Learner Skills and Knowledge

To benefit fully from this lesson, you must have these prerequisite skills and knowledge: General knowledge of telephony technology, including customer premises equipment (CPE) and the PSTN

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Outline

The outline lists the topics included in this lesson

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Basic Components of a Telephony Network

This topic introduces the components of traditional telephony networks

Basic Components of a Telephony Network

A number of components must be in place for an end-to-end call to succeed These components are shown in the figure and include the following:

Edge devices Local loops Private or central office (CO) switches Trunks

Edge Devices

The two types of edge devices that are used in a telephony network include:

Analog telephones: Analog telephones are most common in home, small office/home office (SOHO), and small business environments Direct connection to the PSTN is usually made by using analog telephones Proprietary analog telephones are occasionally used in conjunction with a PBX These telephones provide additional functions such as

speakerphone, volume control, PBX message-waiting indicator, call on hold, and personalized ringing

Digital telephones: Digital telephones contain hardware to convert analog voice into a digitized stream Larger corporate environments with PBXs generally use digital telephones Digital telephones are typically proprietary, meaning that they work with the PBX or key system of that vendor only

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Tie trunk: A dedicated circuit that connects PBXs directly

CO trunk: A direct connection between a local CO and a PBX Interoffice trunk: A circuit that connects two local telephone company COs

Example: Telephony Components

The telephone installed in your home is considered an edge device because it terminates the service provided by your local telephone company PBXs or key systems installed in a business would also be considered edge devices The local loop is the pair of wires that come to your house to provide residential telephone service Trunks are the interconnections between

telephone switches They can be between private switches or telephone company switches

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CO Switches

This topic describes how CO switches function and make switching decisions

Central Office Switches

The figure shows a typical CO switch environment The CO switch terminates the local loop and makes the initial call-routing decision

The call-routing function forwards the call to one of the following:

Another end-user telephone, if it is connected to the same CO Another CO switch

A tandem switch The CO switch makes the telephone work with the following components:

Battery: The battery is the source of power to both the circuit and the telephone It determines the status of the circuit When the handset is lifted to let current flow, the telephone company provides the source that powers the circuit and the telephone Because the telephone company powers the telephone from the CO, electrical power outages should not affect the basic telephone

Note Some telephones on the market offer additional features that require a supplementary power

source that the subscriber supplies; for example, cordless telephones Some cordless telephones may lose function during a power outage

Current detector: The current detector monitors the status of a circuit by detecting whether it is open or closed The table here describes current flow in a typical telephone

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Current Flow in a Typical Telephone

Off cradle Off hook/closed circuit Yes

Dial-tone generator: When the digit register is ready, the dial-tone generator produces a dial tone to acknowledge the request for service

Dial register: The digit register receives the dialed digits

Ring generator: When the switch detects a call for a specific subscriber, the ring generator alerts the called party by sending a ring signal to that subscriber

You must configure a PBX connection to a CO switch that matches the signaling of the CO switch This configuration ensures that the switch and the PBX can detect on hook, off hook, and dialed digits coming from either direction

CO Switching Systems

Switching systems provide three primary functions:

Call setup, routing, and teardown Call supervision

Customer ID and telephone numbers

CO switches switch calls between locally terminated telephones If a call recipient is not locally connected, the CO switch decides where to send the call based on its call-routing table The call then travels over a trunk to another CO or to an intermediate switch that may belong to an inter-exchange carrier (IXC) Although intermediate switches do not provide dial tone, they act as hubs to connect other switches and provide interswitch call routing

PSTN calls are traditionally circuit-switched, which guarantees end-to-end path and resources Therefore, as the PSTN sends a call from one switch to another, the same resource is associated with the call until the call is terminated

Example: CO Switches

CO switches provide local service to your residential telephone The CO switch provides dial tone, indicating that the switch is ready to receive digits When you dial your phone, the CO switch receives the digits, then routes your call The call routing may involve more than one switch as the call progresses through the network

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Private Switching Systems

In a corporate environment, where large numbers of staff need access to each other and the outside, individual telephone lines are not economically viable This topic explores PBX and key telephone system functionality in environments today

What Is a PBX?

A PBX is a smaller, privately owned version of the CO switches used by telephone companies Most businesses have a PBX telephone system, a key telephone system, or Centrex service Large offices with more than 50 telephones or handsets choose a PBX to connect users, both in-house and to the PSTN

PBXs come in a variety of sizes, from 20 to 20,000 stations The selection of a PBX is

important to most companies because a PBX has a typical life span of seven to ten years All PBXs offer a standard, basic set of calling features Optional software provides additional capabilities

The figure illustrates the internal components of a PBX It connects to telephone handsets using line cards and to the local exchange using trunk cards

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A PBX has three major components:

Terminal interface: The terminal interface provides the connection between terminals and PBX features that reside in the control complex Terminals can include telephone handsets, trunks, and lines Common PBX features include dial tone and ringing

Switching network: The switching network provides the transmission path between two or more terminals in a conversation For example, two telephones within an office

communicate over the switching network

Control complex: The control complex provides the logic, memory, and processing for call setup, call supervision, and call disconnection

Example: PBX Installations

PBX switches are installed in large business campuses to relieve the public telephone company switches from having to switch local calls When you call a coworker locally in your office campus, the PBX switches the call locally instead of having to rely on the public CO switch The existence of PBX switches also limits the number of trunks needed to connect to the telephone companys CO switch With a PBX installed, every office desktop telephone does not need its own trunk to the CO switch Rather, the trunks are shared among all users

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What Is a Key System?

Small organizations and branch offices often use a key telephone system, because a PBX offers functionality and extra features that they may not require A key system offers small businesses distributed answering from any telephone, unlike the central answering position required for a PBX

Today, key telephone systems are either analog or digital and are microprocessor-based Key systems are typically used in offices with 30 to 40 users, but can be scaled to support over

100 users

A key system has three major components:

Key service unit: A key service unit (KSU) holds the system switching components, power supply, intercom, line and station cards, and the system logic

System software: System software provides the operating system and calling-feature software

Telephones (instruments or handsets): Telephones allow the user to choose a free line and dial out, usually by pressing a button on the telephone

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Comparing Key Systems with PBXs

Larger companies use proprietary telephone networks with PBXs In a key telephone system, each telephone has multiple lines that allow users to access outside lines to their CO When a call comes into the company, a line or a key lights up on the telephone and indicates that a particular line is in use Users can call another extension or let another person know where to pick up a call by using an intercom function, such as an overhead paging system or

The main difference between a key telephone system and a hybrid telephone system is whether

a single-line telephone can access a single CO local loop or trunk (key telephone system) only,

or whether the single-line telephone can access a pool of CO local loops or trunks (hybrid telephone system)

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Call Signaling

Call signaling, in its most basic form, is the capacity of a user to communicate a need for service to a network The call-signaling process requires the ability to detect a request for service and termination of service, send addressing information, and provide progress reports to the initiating party This functionality corresponds to the three call-signaling types discussed in this topic: supervisory, address, and informational signaling

Basic Call Setup

The figure shows the three major steps in an end-to-end call These steps include:

1 Local signaling originating side: The user signals the switch by going off hook and sending dialed digits through the local loop

2 Network signaling: The switch makes a routing decision and signals the next, or

terminating, switch through the use of setup messages sent across a trunk

3 Local signaling terminating side: The terminating switch signals the call recipient by sending ringing voltage through the local loop to the recipient telephone

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Supervisory Signaling

A subscriber and telephone company notify each other of call status with audible tones and an exchange of electrical current This exchange of information is called supervisory signaling There are three different types of supervisory signaling:

On hook: When the handset rests on the cradle, the circuit is on hook The switch prevents current from flowing through the telephone Regardless of the signaling type, a circuit goes

on hook when the handset is placed on the telephone cradle and the switch hook is toggled

to an open state This prevents the current from flowing through the telephone Only the ringer is active when the telephone is in this position

Off hook: When the handset is removed from the telephone cradle, the circuit is off hook The switch hook toggles to a closed state, causing circuit current to flow through the electrical loop The current notifies the telephone company equipment that someone is requesting to place a telephone call When the telephone network senses the off-hook connection by the flow of current, it provides a signal in the form of a dial tone to indicate that it is ready

Ringing: When a subscriber makes a call, the telephone sends voltage to the ringer to notify the other subscriber of an inbound call The telephone company also sends a ringback tone to the caller alerting the caller that it is sending ringing voltage to the recipient telephone Although the ringback tone sounds similar to ringing, it is a call-progress tone and not part of supervisory signaling

Note The ringing tone in the United States is 2 seconds of tone followed by 4 seconds of silence

Europe uses a double ring followed by 2 seconds of silence

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Dual tone multifrequency: Each button on the keypad of a touch-tone pad or push-button telephone is associated with a set of high and low frequencies On the keypad, each row of keys is identified by a low-frequency tone and each column is associated with a high-frequency tone The combination of both tones notifies the telephone company of the number being called, thus the term dual tone multifrequency (DTMF)

Pulse: The large numeric dial-wheel on a rotary-dial telephone spins to send digits to place

a call These digits must be produced at a specific rate and within a certain level of tolerance Each pulse consists of a break and a make, which are achieved by opening and closing the local loop circuit The break segment is the time during which the circuit is open The make segment is the time during which the circuit is closed The break-and-make cycle must correspond to a ratio of 60 percent break to 40 percent make

A governor inside the dial controls the rate at which the digits are pulsed; for example, when a subscriber calls someone by dialing a digit on the rotary dial, a spring winds When the dial is released, the spring rotates the dial back to its original position While the spring rotates the dial back to its original position, a cam-driven switch opens and closes the connection to the telephone company The number of consecutive opens and closes, or breaks and makes, represents the dialed digit

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