IP TELEPHONY

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What Is IP Telephony?

VoIP and Internet Telephony both refers to

communications services carried over IP (Internet

Protocol) rather than over the Public Switched

Telephone Network (PSTN)

Definition : Internet Telephony, or Voice over Internet Protocol, is a method for taking analog audio signals, like the kind you hear when you talk on the phone, and turning them into digital data that can be transmitted over the Internet.

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Definition : Internet Telephony, or Voice over

Internet Protocol, is a method for taking analog audio

signals, like the kind you hear when you talk on the

phone, and turning them into digital data that can be

transmitted over the Internet.

ABSTRACT

Internet telephony is a novel and cheaper method of communication

and conducting business over the Internet.

The practical upshot of this is that by using some of the free Internet

Telephony software that is available to make Internet phone calls,

you are bypassing the phone company (and its charges) entirely.

IP Telephony 4

INTRODUCTION

Internet telephony uses the Internet protocol to send

audio, video an data between two or more users in the real

time.

IP telephony is the integration and convergence of voice

and data networks, services, and applications.

The main motivation of development of IP Telephony is

the cost saving & integrating new services.5

Introduction (cont…)

Vocaltec introduced the first Internet telephony software

product in early 1995. Running a multimedia PC, the Vocaltec

Internet Phone.

In 1996, Vocaltec with an Intel Company announced to

produce the first IP telephony gateway.

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Classification of IP Telephony :

The classification of IP Telephony is based on three characteristics.

They are.,

* Terminal devices

* Gateways

* Means of transmission

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Terminal devices & Gateways: The most common

way of classifying IP Telephony combines the first

two of these three characteristics the nature of the

terminal devices used and the physical location of the

gateways which must be employed to interconnect IP

networks and the PSTN to provide end-to-end service.

IP Telephony 8

Means of transmission: The third characteristic

introduced above, the nature of the principal underlying means

of transmission. The following definitions are offered as a

means of interpreting the many different terms which are

thrown about in this field:

• Internet Protocol (IP) Telephony

• Public Telephony

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Types of IP Telephony:

PC-to-PC

PC-to-PHONE

PHONE-to-PHONE

PHONE-to-PC

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PC-to-PC It was the first generation IP Telephony.Users on both

ends of a PC-to-PC ‘call’ require a personal computer

(PC) equipped with audio capabilities, the same software,

and an Internet connection.

Calls generally have to be pre-arranged because there is

no way of ‘ringing’ the other user, if he or she is not

online at the desired time. PC-to-PC calling is well-suited

to Internet applications such as “chat rooms”service .

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PC to PC

Phone-to-phone over IP using Gateways

Phone-to-phone over IP Using Adapter Boxes

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PC-to-PHONE:

• From the service provider’s point of view, PC-to-

Phone calling is more complex than simple PC-to-PC

calling because calls need to be billed and routing

arrangements negotiated.

• For that reason, many service providers

restrict this service to a limited range where quality-

of-service requirements are not so demanding

(because duplex communication is not a requirement).15

PC-to-Phone or Phone-to-PC

Different types of IP telephony Standards

H.323 standard

Session initiation protocol (SIP)

Media gateway to media controller protocol (MGCP)

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What is H.323

The H.323 standard for the transmission of real-time

audio, video, and data communications over packet-

based networks based on IP telephony.

H.323 is a standard produced by the ITU-T Study

Group 16.

Currently the most widely-supported IP telephony

signaling protocol.

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H.323 Components

Terminals

Gateways

Multipoint Control Units (MCUs)

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Terminals :H.323 terminal can either be a personal computer or a stand-alone device, running an H.323 and the multimedia applications.

Gateways :An H.323 gateway provides connectivity between an H.323 network and a non-H.323 network.

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Multipoint Control Units:

MCUs provide support for conferences of three or

more H.323 terminals.

All terminals participating in the conference

establish a connection with the MCU.

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Protocols Specified by H.323 :

real-time transfer protocol (RTP)

real-time control protocol (RTCP)

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Real-Time Transport ProtocolReal-time transport protocol (RTP) provides end-

to-end delivery services of real time audio and video.

RTP is used to transport data via the user datagram protocol

Real-Time Control Protocol (RTCP) RTCP provides control services for RTP.

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H.323 Call Establishment

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H.323 Control signaling Flows

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Advantages:

1.Reduced administration as well as network costs

2.Guaranteed service delivery

3.Enhanced operational efficiencies

4.Effectively bring together mobile and remote employees

5.Add innovative features including hardware

6.Reduced telecom cost via toll by pass

7.Effective as well as efficient management of your fax,

voicemail, and email messages

8.free of cost

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Dis-advantages:Exposure to Denial of Service attacks

Challenging emergency calls

Easy congestion

Limited or no use in the absence of a dedicated internet access

CONCLUSION

Internet telephony is cost savings and integrating new services.

Many public telecommunication operators are establishing their own IP telephony services, and using IP-based networks as alternative transmission platforms.

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24/08/2005 IP Telephony 29