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VoIP Presentation by Hüseyin Savran - A Change of Perspective towards IP Telephony

Explore the history of PSTN and the transition to IP Telephony with a focus on the economic and communication benefits. Discover the basic idea behind VoIP technology, encoding, transmission, and playback processes, as well as signaling systems and protocols for setting up calls efficiently. Learn about the components of a basic IP telephone system and the importance of backward compatibility with PSTN networks.

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VoIP Presentation by Hüseyin Savran - A Change of Perspective towards IP Telephony

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  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 Ankara, METU PSTN Call Direction

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

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

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

  7. A Change of Perspective Content Data Reality Web Devices Apps Voice Users Video Email File Transfer Cable Wireless Satellite Fiber

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

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

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

  18. Basic Idea Behind VoIP • Continuously sample audio. • Convert each sample to digital form. • Send the resulting digitizedstream 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. 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.

  22. 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

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

  26. 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

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

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