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1. IP TELEPHONY
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2. 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)
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3. 3
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.

4. 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

5. 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.
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6. 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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7. 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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8. 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

9. 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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10. Types of IP Telephony:
PC-to-PC
PC-to-PHONE
PHONE-to-PHONE
PHONE-to-PC
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11. 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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12. PC to PC

13. Phone-to-phone over IP
using Gateways

14. Phone-to-phone over IP Using
Adapter Boxes
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15. 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

16. PC-to-Phone or Phone-to-PC

17. Different types of IP telephony Standards
H.323 standard
Session initiation protocol (SIP)
Media gateway to media controller protocol (MGCP)
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18. 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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19. H.323 Components
Terminals
Gateways
Multipoint Control Units (MCUs)
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20. 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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21. 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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22. Protocols Specified by H.323 :
real-time transfer protocol (RTP)
real-time control protocol (RTCP)
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23. Real-Time Transport Protocol
Real-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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24. H.323 Call Establishment
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25. H.323 Control signaling Flows
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26. 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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27. 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

28. 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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29. 24/08/2005 IP Telephony 29