VoIP PRESENTATION

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VoIP PRESENTATION

• BY
• HÜSEYIN SAVRAN
• 220702044

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OUTLINE

• PSTN an brief history of telephone

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PSTN ( Public Switched Telephone Network)

• Known structure of conventional telephone network.

Istanbul, yeditepe
Ankara, METU
PSTN
Call Direction
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PSTN history

• Since the telephone was invented
• in the late 1800s, telephone communication has
  not changed substantially .

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A Change of Perspective
Cable
Traditional View
Broadcast
Telephony
Data
Wireless
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A Change of Perspective
Cable
Current View
Data
Broadcast
Telephony
Wireless
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A Change of Perspective
Content
Data
Reality
Web
Devices
Apps
Voice
Users
Video
Email
File Transfer
Cable
Wireless
Satellite
Fiber
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These Count as Phones?
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MOTIVATION
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What is VoIP

• IP TELPHONY (VOICE over IP)
• Transmission of voice telephone calls
• using internet infrastructure.

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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.

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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 isnt any internet cafe
  which doesnt have tiny video cameras over their
  monitors.

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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!

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Keep in mind!

• IP Telephony must be backward compatible with
  existing PSTN.
• There are several communication schemes

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VoIP to VoIP
Broadband Network
VoIP
VoIP
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VoIP to POTS with Internet
Internet/Broadband
Istanbul, yeditepe
New Delhi
PSTN
VoIP
Server/Gateway India
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VoIP to POTS without Internet
Server/Gateway
Istanbul, kayisdagi
Miami, FL
PSTN
CO
Miami
VoIP
LATA
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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.

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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.

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• 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.

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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.

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Why 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

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What does real-time clock value do?

• Allows a receiver to construct the axact temporal
  sequence of the data.
• If a packet is missing , the receiver knows
  exactly how long to wait before starting to play
  the next packet

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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.

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Signaling Protocols

• IETF?Session Initiation Protocol (SIP)
• ITU?H.323
• Aboves must be able to interact with SS7

Internet/Broadband
New Delhi
Istanbul, yeditepe
PSTN
VoIP
Server/Gateway India
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A Basic IP Telephone System

• Two basic components interconnected by an IP
  internet.
• IP telephone
• Media Gateway Controller

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