What is VOIP and how it works.

1. VOICE OVER INTERNET PROTOCOL
(VOIP)
Presented by
JAASIR NAZIR WANI
M.Tech SE
132262601006

2. PSTN (PUBLIC SWITCHED TELEPHONE NETWORK)
 Since the telephone was invented in the late 1800s,
telephone communication has not changed substantially.
 Known structure of conventional telephone network.
Chennai
PSTN
New Delhi
Call Direction

3. A CHANGE OF PERSPECTIVE
Traditional View
Telephony
Cable
Broadcast
Wireless
Data

4. A CHANGE OF PERSPECTIVE
Current View
Cable
Broadcast
Wireless
Telephony
Data

5. A CHANGE OF PERSPECTIVE
Reality
Data
Email
Voice
Web
VideoFile
Transfer

6. WHAT IS VOIP
 VOIP allows you to make telephone calls using a
computer network, over a data network like the Internet.
 VOIP is a technology whereby voice conversations are
compressed digitized, encapsulate inside of IP packets
and transported over a data network.
 The main difference is that the traditional wired network
we have been using for years allows only one caller per
channel and VOIP compression allows many callers
per channel.
 Many names, different meaning to different people:
 Soft-switching
 Next Generation Voice Network
 IP Telephony
 Voice over Internet
 Voice over Internet Protocol
 Voice over Packet
 IP Communications

7. WHY NEED IP TELEPHONY
 Economic: (uses internet, IP routers...)
 Further savings: Because underlying
network infrastructure can be shared.
a single set of equipment, wiring, network connection
enough.
Example: a company with reduced telephone costs.
 Not only voice but also video: is transmitted using
similar concepts.
 Independent: Much larger selection of service
providers to provide voice and video communication
services.
No geographical restriction!
Located virtually anywhere in the world!

8. HOW DOES IT WORK
 Continuously sample audio
 Convert each sample to digital form
 Send digitized stream across Internet in packets
 Convert the stream back to analog for playback
 VOIP technology (also called "Packet Switching") does not use
direct connections.
 As there is no direct connection, packets with different
destinations may follow the same path, and those with the same
destinations may follow divergent paths depending on network
conditions.

9. ADVANTAGES USING VOIP RATHER PSTN?
 When you are using PSTN line, you typically pay for time used
to a PSTN line manager company: more time you stay at
phone and more you'll pay. In addition you couldn't talk with
other that one person at a time.
 In opposite with VoIP mechanism you can talk all the time with
every person you want (the needed is that other person is also
connected to Internet at the same time), as far as you want
(money independent) and, in addition, you can talk with many
people at the same time.
 At the same time, you can exchange data with people you are
talking with, sending images, graphs and videos.

10. APPLICATION OF VOIP
 Enterprise Environment Application
 The Remote Worker / Branch Office application
 The Residential Application

11. BASIC SYSTEM COMPONENTS OF VOIP
•CLIENTS
•SERVERS
•GATEWAYS
A general VOIP network

12. KEEP IN MIND!
 Challenge
 Voice transmission delay
 Call setup: call establishment, call termination, etc.
 Backward compatibility with existing PSTN (Public
Switched Telephone Network)
 There are several communication schemes:

13. VOIP TO VOIP
Broadband Network
Call Direction
IP Protocol
VoIP VoIP
New York, USA New Delhi, India

14. VOIP TO POTS WITH INTERNET
Internet/Broadband
PSTN
Server/Gateway
India
New York, USA New Delhi,India
Call Direction
IP Protocol
VoIP

15. VOIP TO POTS WITHOUT INTERNET
PSTN
Server/Gateway
India
New York, USA New Delhi, India
Call Direction
IP Protocol
VoIP

16. ENCODING, TRANSMISSION, AND PLAYBACK
 Two groups have introduced standards for IP
telephony
 International Telecommunications Union(ITU),
controls telephone standards.
 Internet Engineering Task Force(IETF), controls
TCP/IP standards.

17. CONT…
 Encoding: Pulse Code Modulation (PCM)
 Transmission: Real-Time Transport Protocol (RTP)
Note: RTP is not a tranport-layer protocol. It is a tranfer protocol that
operates at Layer 5.
 Each RTP message is encapsulated in UDP datagram,
which is then encapsulated in an IP datagram for
transmission.

18. WHY UDP INSTEAD OF TCP?
 Higher overhead of TCP does not make sense for
telephone call. Because audio must stream! No wait for
missing packets. Play missing part as silence.
 UDP Offerrs best-effort delivery, to handle duplication,
delay, out-of-order delivery.
 Each RTP message contains:
 A sequence number
 A real-time clock value

19. WHAT DOES REAL-TIME CLOCK VALUE DO?
 Allows a receiver to construct the exact temporal
sequence of the data.
 İf a packet is missing , the receiver knows exactly how long
to wait before starting to play the next packet

20. CONCLUSION
 VOIP means Voice Over Internet Protocol, or Voice
over Internet, IP Telephony.
 Hot area both in research and market because of low
cost.
 Challenge in backward compatibility with PSTN.
 It uses UDP instead of TCP for voice transmission.
 It follows the standards of ITU and IETF.

21. THANK YOU