VoIP PRESENTATION
BY
HÜSEYİN SAVRAN
220702044
OUTLINE
 PSTN

an brief history of telephone
PSTN ( Public Switched Telephone Network)
 Known

structure of conventional
telephone network.
İstanbul, yeditepe

PSTN

...
PSTN history
 Since

the telephone was invented
in the late 1800s, telephone
communication has not changed
substantially ...
A Change of Perspective
Traditional View

Cable

Data

Broadcast

Telephony
Wireless
A Change of Perspective
Current View
Data

Cable

Broadcast

Telephony
Wireless
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
...
These Count as Phones?
MOTIVATION
What is VoIP



IP TELPHONY (VOICE over IP)
Transmission of voice telephone calls
using internet infrastructure.
Why need to IP Telephony?



Economic (uses internet, IP routers...)
Further savings. Because underlying
network infrast...
Why need to IP Telephony?
Cont.





Not only voice but also video
is transmitted using similar
concepts.
Spreads at a f...
Why need to IP Telephony?
Cont.



Independent. Much larger
selection of service providers to
provide voice and video
com...
Keep in mind!




IP Telephony must be backward
compatible with existing PSTN.
There are several communication
schemes:
VoIP to VoIP
Broadband Network

VoIP

VoIP

Call Direction
IP Protocol
VoIP to POTS with Internet
İstanbul, yeditepe

Internet/Broadband

New Delhi

PSTN

VoIP

Server/Gateway
India
Call Direct...
VoIP to POTS without Internet
Server/Gateway
İstanbul, kayışdağı

VoIP

Miami, FL

PSTN

CO

LATA

Call Direction
IP Proto...
Basic Idea Behind VoIP
 Continuously

sample audio.
 Convert each sample to digital form.
 Send the resulting digitized...
Encoding, Transmission, and Playback
 Two

groups have introduced standards
for IP telephony
International Telecommunicat...



Encoding Pulse Code Modulation (PCM)
TransmissionReal-Time Transport
Protocol (RTP)
Note: RTP is not a tranport-lay...
W hy UDP instead of
TCP?
 Higher overhead of TCP does not
make sense for telephone call.
Because audio must stream! No wa...
W hy UDP instead of
TCP?
 UDP Offerrs best-effort delivery. to
handle duplication, delay, out-of-order
delivery, each RTP...
What does real-time
clock value do?
• Allows a receiver to construct the
axact temporal sequence of the data.
– İf a packe...
Signaling Systems and Protocols
 Signaling:

The process of establishing and
terminating a call. Includes:
–
–
–

Mapping...
Signaling Protocols
 IETFSession

Initiation Protocol (SIP)

 ITUH.323

Aboves must be able to interact with SS7
Inter...
A Basic IP Telephone System
Two basic components interconnected by an IP
internet.
*IP telephone
*Media Gateway Controller...
Media Gateway Controller

Media gateway handles
voice

IP telephone

INTERNET

PSTN

Signaling gateway
handles setup

Anal...
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Voip

  1. 1. VoIP PRESENTATION BY HÜSEYİN SAVRAN 220702044
  2. 2. OUTLINE  PSTN an brief history of telephone
  3. 3. PSTN ( Public Switched Telephone Network)  Known structure of conventional telephone network. İstanbul, yeditepe PSTN Call Direction Ankara, METU
  4. 4. PSTN history  Since the telephone was invented in the late 1800s, telephone communication has not changed substantially .
  5. 5. A Change of Perspective Traditional View Cable Data Broadcast Telephony Wireless
  6. 6. A Change of Perspective Current View Data Cable Broadcast Telephony Wireless
  7. 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. 8. These Count as Phones?
  9. 9. MOTIVATION
  10. 10. What is VoIP   IP TELPHONY (VOICE over IP) Transmission of voice telephone calls using internet infrastructure.
  11. 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. 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. 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. 14. Keep in mind!   IP Telephony must be backward compatible with existing PSTN. There are several communication schemes:
  15. 15. VoIP to VoIP Broadband Network VoIP VoIP Call Direction IP Protocol
  16. 16. VoIP to POTS with Internet İstanbul, yeditepe Internet/Broadband New Delhi PSTN VoIP Server/Gateway India Call Direction IP Protocol
  17. 17. VoIP to POTS without Internet Server/Gateway İstanbul, kayışdağı VoIP Miami, FL PSTN CO LATA Call Direction IP Protocol Miami
  18. 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. 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. 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. 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. 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. 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. 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. 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. 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. 27. Media Gateway Controller Media gateway handles voice IP telephone INTERNET PSTN Signaling gateway handles setup Analog telephone

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