© 2006 Cisco Systems, Inc. All rights reserved.

2.1 - Introducing VoIP Networks

© 2006 Cisco Systems, Inc. All rights reserved.

Objectives Describe the benefits of a VoIP network.

Describe the components of a VoIP network.

Describe the legacy analog interfaces used in VoIP networks.

Describe the digital interfaces used in VoIP networks.

Explain the 3 phases of call control.

Compare and contrast distributed and centralized call control.

© 2006 Cisco Systems, Inc. All rights reserved.

Benefits of a VoIP Network More efficient use of bandwidth and equipment Lower transmission costs Consolidated network expenses Improved employee productivity through features

provided by IP telephony:IP phones are complete business communication devices.

Directory lookups and database applications (XML)Integration of telephony into any business application

Software-based and wireless phones offer mobility.

Access to new communications devices (such as PDAs and cable set-top boxes)

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Components of a VoIP Network

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Legacy Analog and VoIP Applications Can Coexist

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Legacy Analog Interfaces in VoIP Networks

Analog Interface Type Label Description

Foreign Exchange Station FXS Used by the PSTN or PBX side of an FXS–FXO connection

Foreign Exchange Office FXO Used by the end device side of an FXS–FXO connection

Earth and Magneto E&M Trunk, used between switches

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Legacy Analog Interfaces in VoIP Networks

1

1

23

4

5

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Digital Interfaces

Interface Voice Channels (64 kbps Each) SignalingFraming Overhead

Total Bandwidth

BRI 2 1 channel (16 kbps) 48 kbps 192 kbps

T1 CAS 24 (no clean 64 kbps because of robbed-bit signaling)

in-band (robbed-bits in voice channels)

8 kbps 1544 kbps

T1 CCS 23 1 channel (64 kbps) 8 kbps 1544 kbps

E1 CAS 30 64 kbps 64 kbps 2048 kbps

E1 CCS 30 1 channel (64 kbps) 64 kbps 2048 kbps

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Call Setup

Checks call-routing configuration

Determines bandwidth availability

If bandwidth is available, setup message is passed

If bandwidth is not available, busy signal is generated

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Call Maintenance

Tracks quality parameters:

Packet loss

Jitter

Delay

Maintains or drops call based on connection quality

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Call Teardown

Notifies devices to free resources

Resources are made available to subsequent calls

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Distributed Call Control

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Centralized Call Control

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Self Check

1. Which type of call control uses a call agent to route the call?

2. What is a DSP?

3. Name 3 types of analog interfaces used at gateways.

4. What are the 3 components of basic call control?

5. What phase of call control involves determining if bandwidth is available to place the call?

© 2006 Cisco Systems, Inc. All rights reserved.

Summary The benefits of a VoIP network include more efficient

use of network bandwidth and equipment, lower cost and consolidated expenses.

Legacy analog and VoIP applications and devices can coexist.

The 3 stages of a VoIP call include call setup, call maintenance, and call teardown.

VoIP can be deployed in a centralized or distributed environment.