This document provides an overview of VoIP (Voice over IP) technology. It begins with a brief history of traditional telephone networks and an explanation of how VoIP utilizes Internet infrastructure to transmit voice calls. Key benefits of VoIP include lower costs compared to traditional phone networks since the same wiring and equipment can be used for both data and voice. Standards bodies have developed protocols for encoding, transmitting, and decoding voice streams over IP networks. Signaling protocols like SIP and H.323 are used to set up calls by mapping phone numbers to IP addresses. A basic VoIP system includes IP phones and a media gateway controller to interface with the public switched telephone network.

1. VoIP PRESENTATION
BY
HÜSEYİN SAVRAN
220702044

2. OUTLINE
 PSTN
an brief history of telephone

3. PSTN ( Public Switched Telephone Network)
 Known
structure of conventional
telephone network.
İstanbul, yeditepe
PSTN
Call Direction
Ankara, METU

4. PSTN history
 Since
the telephone was invented
in the late 1800s, telephone
communication has not changed
substantially .

5. A Change of Perspective
Traditional View
Cable
Data
Broadcast
Telephony
Wireless

6. A Change of Perspective
Current View
Data
Cable
Broadcast
Telephony
Wireless

7. A Change of Perspective
t
en
t
on
C
s
ce
i
ev
D
ps
Ap
Reality
Web
Voice
Email
e
bl
ss
Ca
le
e
ire
lit
l
W
r
te
be
Sa
Fi
s
er
Us
Data
Video
File
Transfer

8. These Count as Phones?

9. MOTIVATION

10. What is VoIP


IP TELPHONY (VOICE over IP)
Transmission of voice telephone calls
using internet infrastructure.

11. Why need to 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.

12. Why need to IP Telephony?
Cont.


Not only voice but also video
is transmitted using similar
concepts.
Spreads at a fast pace.
For instance there isn’t any
internet cafe which doesn’t have
tiny video cameras over their
monitors.

13. Why need to IP Telephony?
Cont.

Independent. Much larger
selection of service providers to
provide voice and video
communication services .
No geographical restriction!
Located virtually anywhere in
the
world!

14. Keep in mind!


IP Telephony must be backward
compatible with existing PSTN.
There are several communication
schemes:

15. VoIP to VoIP
Broadband Network
VoIP
VoIP
Call Direction
IP Protocol

16. VoIP to POTS with Internet
İstanbul, yeditepe
Internet/Broadband
New Delhi
PSTN
VoIP
Server/Gateway
India
Call Direction
IP Protocol

17. VoIP to POTS without Internet
Server/Gateway
İstanbul, kayışdağı
VoIP
Miami, FL
PSTN
CO
LATA
Call Direction
IP Protocol
Miami

18. Basic Idea Behind VoIP
 Continuously
sample audio.
 Convert each sample to digital form.
 Send the resulting digitized stream
accross an IP network in packets.
 Convert the stream back to analog for
playback.
 Before the procedure above, the system
must handle call setup. Phnumber to IP.

19. 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.

20. 

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.

21. W hy 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.

22. W hy UDP instead of
TCP?
 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

23. What does real-time
clock value do?
• Allows a receiver to construct the
axact 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

24. Signaling Systems and Protocols
 Signaling:
The process of establishing and
terminating a call. Includes:
–
–
–
Mapping a phone number to location
Finding a route to the called party
Handling other details such as call forwarding
 Signaling
System 7 (SS7) for traditional
telephone system.

25. Signaling Protocols
 IETFSession
Initiation Protocol (SIP)
 ITUH.323
Aboves must be able to interact with SS7
Internet/Broadband
İstanbul, yeditepe
New Delhi
PSTN
VoIP
Call Direction
Server/Gateway
India
IP Protocol

26. A Basic IP Telephone System
Two basic components interconnected by an IP
internet.
*IP telephone
*Media Gateway Controller
Media Gateway Controller
IP telephone
INTERNET
IP telephone

27. Media Gateway Controller
Media gateway handles
voice
IP telephone
INTERNET
PSTN
Signaling gateway
handles setup
Analog
telephone