DAY 1

Introduction Welcome to the world of CCNA Voice! As technology continues to evolve, the realm of voice, which was traditionally kept completely separate from data, has now begun to merge with the data network. This brings together two different worlds of people: data Technicians and voice technicians . One of the primary goals of the new CCNA Voice certification is to bridge these two worlds together. This course help you to pass the ICOMM 8.0 exam and make you much more knowledgeable .

ICONS USED IN THIS BOOK

Exam Number: 640-461 ICOMM

Associated Certifications: CCNA Voice

Duration: 90 minutes (60-70 questions)

Available Languages: English and Japanese

640-461 ICOMM v8.0

Introducing Cisco Voice and Unified

Communications Administration

Where It All Began: Analog Connections The Evolution: Digital Connections Understanding the PSTN The New Yet Not-So-New Frontier: VoIP

Where It All Began: Analog Connections In 1877, Thomas Edison created a brilliant device known as a phonograph

Sound-Collecting Horn

Cylinder Coated with Tinfoil

Electrical signals to capture the properties of voice.

H E L L O

ON-HOOK MODE

OFF-HOOK MODE

MAKING A CALL

How the analog phone works ?

The connections of the tip and ring wire to your analog phone.

LOOP START SIGNALING

PROBLEM WITH LOOP START SIGNALING Loop start signaling is susceptible to a problem known as GLARE .

Ground start signaling originated from its implementation in pay phone systems.

GROUND START SIGNALING

The types of signaling in the analog world include : 1. Supervisory signaling (on hook, off hook, ringing) 2. Informational signaling (dial tone, busy, ringback and so on) 3. Address signaling (dual-tone multifrequency (DTMF) and Pulse).

Types Of Signaling

The Evolution: Digital Connections

Analog signaling was a massive improvement over tin cans and string, but still posed plenty of problems of their own.

To increase the distance the analog signal could travel,the phone company had to install repeaters to regenerate the signal as it became weak.

Because Of Some Disadvantages Analog is Moving to Digital 1.Distance Limitation 2.Wiring Requirements

1.Distance Limitation

The second difficulty encountered with analog connections was the sheer number of wires the phone company had to run to support a large geographical area or a business with a large number of phones.

2.Wiring Requirements

Moving from Analog to Digital

ANALOG DIGITAL

Digital voice uses a technology known as time-division multiplexing (TDM).

Time-division multiplexing (TDM)

TDM (contd.) Digital voice connections to the PSTN as 1. T1 circuits in the United States, Canada, and Japan. A T1 circuit is built from 24

separate 64-kbps channels known as a digital signal 0 (DS0).

2. Each one of these channels is able to support a single voice call. 3. Areas outside the United States, Canada, and Japan use E1 circuits, which allow you to use up to 30 DS0s for voice calls.

TWO BASIC METHODS FOR VOICE OVER IP

Signaling for digital circuits: Channel associated signaling (CAS): Signaling information is transmitted using the same bandwidth as the voice.(Robbed Bit Signaling) Common channel signaling (CCS): Signaling information is transmitted using a separate, dedicated signaling channel.(Out-of-Band Signaling)

Channel Associated Signaling

CCS is the most popular connection used between voice systems worldwide because 1. More flexibility with signaling messages

2. More bandwidth for the voice bearer channels, 3. Higher security

COMMON CHANNEL SIGNALING

Tip: When using CCS configurations with T1 lines, the 24th time slot is always the signaling channel. When using CCS configurations with E1 lines, the 17th time slot is always the signaling channel.

Understanding the PSTN

The connection to one massive voice network, known as the PSTN. Its primary purpose is to establish worldwide pathways to allow people to easily connect, converse, and disconnect.

Pieces of the PSTN: Analog telephone Local loop CO switch Trunk Private switch Digital telephone

Understanding the PSTN

Private branch exchange system looks like a large box full of cards. Each card has a specific function: Line cards Trunk cards Control complex

Understanding PBX and Key Systems

Understanding PBX and Key Systems

Each two-wire analog connection has the capability to support a single call.

Connections to and Between the PSTN

Connections to and Between the PSTN

VoIP The amazing process of converting spoken voice into packets. The packet gets to its destination 1. In time (QoS)

2. Choosing the proper coding and decoding (codec) methods

3. Making sure that the VoIP packet doesnt fall into the wrong hands (encryption),

Reduced cost of Communicating: VoIP allows you to forward calls over WAN connections. Reduced cost of cabling: VoIP deployments typically cut cabling costs in half by running a

single Ethernet connection Take your phone with you: Users can take IP phones home with them and retain their work extension. IP Softphones Unified e-mail, voice mail and fax: All messaging can be sent to a users e-mail inbox. Open, compatible standards: Connect devices from different telephony vendors together.

Benefits of VoIP for Business

The Process of Converting Voice to Packets Nyquist found that he could accurately reconstruct audio streams by taking samples that numbered twice the highest audio frequency used in the audio. The Nyquist theorem is able to reproduce frequencies from 3004,000 Hz.

Nyquist Theorem

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, optional step.

A sample is a numeric value that consumes a single byte of information. sampling 8,000 times (2 * 4000) every second.

So, whats a sample?

This process of converting the analog wave into digital, numeric values is known as quantization.

Quantization

8,000 samples a second times the 8 bits in each sample, and you get 64,000 bits per second . G.711 audio codec consumes 64 kbps. Note: There are two forms of the G.711 codec also called as PCM method: -law (used primary in the United States and Japan) and a-law (used everywhere else)makes more sense .

Encoding

segments intervals Positive/negative

Compression Bandwidth Requirements

Using this process, G.729 is able to reduce bandwidth down to 8 kbps for each call. a measurement system known as a Mean Opinion Score (MOS) to rate the quality of the various voice codecs.

Role of Digital Signal Processors Cisco designed its routers with one primary purpose in mind: routing. A DSP is a chip that performs all the sampling, encoding, and compression functions on audio coming into your router.

Cisco bundles these DSP chips into packet voice DSP modules (PVDM), which resemble the Old memory SIMMs.

DSP REQUIREMENT