VoIP Tutorial by Gary Brown

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Publié par	Ustlo
Nombre de lectures	38
Langue	English

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NACT VoIP Industry Tutorial

® ® ®
The fifth and last section describes the NACT VoIP 7 network m odel. This discussion uses NACT IPAX gateways with VoIP 7 signaling in a

In the

– PSTN Circuit - switched Model 6
– H.323 Gateways in a Point to Point Configuration 7
– H.323 Gatekeeper/Gateways in a Point to Multipoint Configuration 8
– Multiple H.323 Gatekeepers in a Multipoint - to - Multipoint Configuration 9
– ISC/IETF Network Model 10
– NACT VoIP 7 Multipoint - to - Multipoint Network Model 11
– NACT VoIP 7 Carrier Signaling Interconnection and IP Network Transport 12
– NACT VoIP 7 Carrier Network Signaling Portals 13

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.......... ................................ ................................ ................................ ................................ - Figure 8
.............................. ................................ ................................ - Figure 7
............................. ................................ ................................ ................................ - Figure 6
................ ................................ ................................ ................................ ................................ ................................ Figure 5
..... ................................ ................................ ................................ Figure 4
............. ................................ ................................ ................................ - - Figure 3
.......... ................................ ................................ ................................ ................................ - - Figure 2
........... ................................ ................................ ................................ ................................ ................................ Figure 1
List of Figures
Text following the figures contains a discussion of what each figure illustrates.
following discussion, references to figures containing diagrams of various network models, their components, and interconnections are given.
Diagrams
carrier networks.
VoIP network to illustrate and discuss the advantages and disadvantages of this VoIP network model, including the interconnection of multiple VoIP
- -
how the different components of their VoIP network model interact. This model’s advantages and disadvantages are discussed.
C (International Softswitch Consortium) views of a VoIP network and The fourth section describes the IETF (Internet Engineering Task Force) and IS
based VoIP network are discussed. - disadvantages of an H.323 protocol
ocol view of VoIP networks and the different configurations the H.323 protocol supports. The advantages and The third section covers the H.323 prot
The second section is a short description and illustration of the current telephone network (the “PSTN”) with its advantages and disadvantages.
require searching out the definitions of other terms.
m’s definition may terms that are defined elsewhere in the glossary in order to minimize the glossary size, which means that fully understanding a ter
st is highly recommended so the other sections can be understood. Many definitions contain acronyms, abbreviations or other Reading this section fir
The first section is a glossary of terms that are used throughout the VoIP industry and in this tutorial. The terms are organized in alphabetical order.
nd managed, including the interconnection of multiple VoIP carrier networks. Inc. as it pertains to how a large VoIP network should be set up a
This tutorial gives background information on the VoIP industry as it exists at the time of this writing, and the view of NACT Telecommunications,
Introduction

Glossary of Terms
100baseT An Access Tandem switch interconnects with CO switches and other access tandem switches to form the PSTN

An application server is an IETF concept. It is most often a computer that implements applications, such as prepaid
“class 5” services, automated operator services, etc., and interfaces with a softswitch in order to permit

Bandwidth is a term used to describe the capacity of a physical circuit or piece of equipment to transport or

Bearer ci rcuits refer to specific circuits that carry only voice and are never used to carry data messages for call

COCentral Office refers to the type of PSTN switch to which telephones and PBX systems are attached. A CO switch
implements features such as call waiting, call forwarding, et c. and interconnects with tandem switches. It is often

DTMF Dual Tone Multi Frequency is a set of 16 tones used for in band signaling between PSTN switches and telep

G.711
produces a bit rate of 64 Kbits/second and has no silence suppression, meaning silence is transmitted and occupies

G.723
the Multi

G.726

G.727 ly called Variable Rate ADPCM, is available in the NACT IPAX VoIP vocoder suite. This
vocoder algorithm allows bit rates of 16 40 Kbits/second for sending and receiving voice. The bit rates can be

G.728

G.729
Prediction), is used in many VoIP gateways. It has a bit rate of 8 Kbits/second. This vocoder algorithm has silence

A gateway in the circuit switched network is a switch that bridges or interfaces two separate PSTN networks, for
European network. Such switches are often called international gateway switches because they interface with and

A gateway is a hardware and software system that converts one type of media to another type of media (e.g., G.711
T1/E1 (TDM

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. In general telephony terms it converts voice from one form to another, based)) - based) to G.723 RTP (IP -
Gateway2
Lucent 5ESS.
or more countries. Examples of such switches are the Nortel DMS 300 and the connect the national networks of two

based, - law PCM, C7 signaling - based, North American network with the A - law PCM, SS7 signaling - mple., the mu exa
- Gateway1
with other gatekeepers, but usually only between those of the same manufacturer.
point situation. Gatekeepers can communicate - to - point - responsible for routing all calls to/from the gateways in a non
A gatekeeper is an H.323 concept and a device or computer that controls one or more gateways within a “zone”. It is Gatekeeper
for which a license fee must be paid.
ed vocoder algorithm suppression, meaning silence is not transmitted and does not occupy bandwidth. This is a patent
Code Excited Linear - e Structure Algebraic ACELP (Conjugat - This vocoder, sometimes known by the abbreviation CS
in some VoIP gateways. It has a bit rate of 16 Kbits/second.
Delay Code Excited Linear Prediction), is used - CELP (Low - This vocoder, sometimes known by the abbreviation LD
on. different in each direction. It has no silence suppressi
-
- This vocoder, common
Kbits/second. This vocoder has no silence suppression, meaning silence is transmitted and occupies bandwidth.
algorithm can produce bit rates of 16, 24, 32, and 40 Kbits/second. The NACT IPAX voice prompts are recorded at 32
er gateway for the playback of voice messages such as authorization code and destination number prompts. This vocod
This vocoder, commonly called ADPCM (Adaptive Differential Pulse Code Modulation), is used in the NACT IPAX
paid.
hich a license must be meaning silence is not transmitted and does not occupy bandwidth, and is patented, the use for w
rate Coder and has two bit rates, 5.3 and 6.4 Kbits/second. This vocoder algorithm has silence suppression, -
oft’s NetMeeting software. It is called This vocoder is commonly used in VoIP gateways and is the vocoder in Micros
bandwidth.
n the rest of the world. This vocoder algorithm law used i - law used in North America and Japan, and A - algorithm; mu
This vocoder is used in the PSTN, and is commonly called PCM (Pulse Code Modulation). There are two flavors of its
The tones can also be used for signaling between switches.
hones. - - -
called a “class 5” switch, a reference to the original AT&T hierarchal network structure.

that is not the original local telephone company. See ILEC.
a geographic area A Competitive Local Exchange Carrier is a local telephone company available to subscribers within CLEC
signaling, such as the ISDN or SS7 data links.
Bearer Circuits
kilobits (thousands of bits), megabits (millions of bits), and gigabits (billions of bits), respectively.
information and is often expressed in terms of bits per second. Common abbreviations are Kbits, Mbits, and Gbits for
switch Bandwidth
interactions with a caller.
calling,
Application Server
network. It is often called a “class 4” switch, a reference to the original AT&T hierarchal network structure.
Access Tandem
45 connectors. - The 100/10 megabits/second Ethernet standard that uses twisted pair wires with RJ
Glossary of TermsISDN
—
—

usually from circuit switched to packet switched. In the ISC/IETF VoIP model, a gateway is a dumb device that

H.248
H.323
and t