Cisco call manager express

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  • Publicado : 14 de diciembre de 2010
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Configuring Cisco CallManager Express (CME)

Cisco Networking Academy Program

IP Telephony

© 2005 Cisco Systems, Inc. All rights reserved.

Cisco Public

1

Overview of Cisco CME

IP Telephony

© 2005 Cisco Systems, Inc. All rights reserved.

Cisco Public

2

What is Cisco CallManager Express?
Cisco CME

Trunks PSTN

WAN

• Call processing for small to mediumsized deployments • VoIP integrated solution • Up to 120 IP phones • IOS based solution
IP Telephony © 2005 Cisco Systems, Inc. All rights reserved.

Cisco Public

3

What is Cisco CallManager Express? (Cont.)
• Select IOS based platform • Multiservice access routers

2600XM

3700

1700

IP Telephony

© 2005 Cisco Systems, Inc. All rights reserved.

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4

How DoesCisco CallManager Express Work?
Connection(s) to PSTN
• Analog • Digital

PSTN

IP Telephony

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5

How Does Cisco CallManager Express/Cisco Unity Express Work? (Cont.)
PSTN
H.323 H.323 H.323 between Cisco CME systems

WAN
H.323 SIP

WAN
PSTN Gateway and IP to IP Gateway functionality

PSTN

PSTN
IP Telephony ©2005 Cisco Systems, Inc. All rights reserved.

Cisco Public

6

Differences between Traditional Telephony and VoIP

IP Telephony

© 2005 Cisco Systems, Inc. All rights reserved.

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7

Basic Components of a Telephony Network

IP Telephony

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8

Central Office Switches

IP Telephony

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9

What Is a PBX?

IP Telephony

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10

What Is a Key System?

IP Telephony

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11

Basic Call Setup

IP Telephony

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12 Digitizing Analog Signals
1. Sample the analog signal regularly 2. Quantize the sample 3. Encode the value into a binary expression 4. Compress the samples to reduce bandwidth (multiplexing), optional step

IP Telephony

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13

Nyquist Theorem

IP Telephony

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14 Quantization

IP Telephony

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15

Quantization Techniques
• Linear
Uniform quantization

• Logarithmic quantization
Compands the signal Provides a more uniform signal-to-noise ratio

• Two methods
α-law (most countries) μ-law (Canada, U.S., and Japan)

IP Telephony

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16

Voice-Compression Techniques
• Waveform algorithms
PCM ADPCM

• Source algorithms
LDCELP CS-ACELP

IP Telephony

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17

Example: Waveform Compression
• PCM
Waveform coding scheme

• ADPCM
Waveform coding scheme Adaptive: automatic companding Differential: encode changes between samplesonly

• ITU standards:
G.711 rate: 64 kbps = (2 x 4 kHz) x 8 bits/sample G.726 rate: 32 kbps = (2 x 4 kHz) x 4 bits/sample G.726 rate: 24 kbps = (2 x 4 kHz) x 3 bits/sample G.726 rate: 16 kbps = (2 x 4 kHz) x 2 bits/sample
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18

Example: Source Compression
• CELP
Hybrid coding scheme

• High-quality voice at lowbit rates, processor intensive • G.728: LDCELP—16 kbps • G.729: CS-ACELP—8 kbps
G.729A variant—8 kbps, less processor intensive, allows more voice channels encoded per DSP Annex-B variant –VAD and CNG

IP Telephony

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19

G.729 and G.729A Comparison
• Both are ITU standards • Both are 8 kbps CS-ACELP • G.729 more complex...
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