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Internet Telephony - PowerPoint PPT Presentation


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Internet Telephony. IP Telephony. Internet telephony refers to communications services—voice, facsimile, and/or voice-messaging applications—that are transported via the Internet, in real time rather than the public switched telephone network (PSTN). . Voice Based Applications.

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PowerPoint Slideshow about 'Internet Telephony' - estelle


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Presentation Transcript
ip telephony
IP Telephony
  • Internet telephony refers to communications services—voice, facsimile, and/or voice-messaging applications—that are transported via the Internet, in real time rather than the public switched telephone network (PSTN).
voice based applications
Voice Based Applications
  • Automated Attendants
  • Voice Prompting
  • Voice Messaging
  • Faxing, Fax Services, Fax Broadcast
  • UnPBX
  • Speech Recognition
  • Text to Speech
ip telephony components
IP Telephony Components
  • Gateway
    • Bridge between Internet and PSTN
  • Gatekeeper
    • Billing
    • Directory services
    • Authentication
    • Bandwidth Control
components
Components
  • Endpoints (Terminals)
  • Miltipoint Control Units (MCUs)
h 323 standard
H.323 Standard
  • H.323 Specification
    • Real-time Transport Control Protocol (RTCP)
      • Session Layer (Monitors quality)
    • Real-time Transport Protocol (RTP)
      • Transport Layer (error control)
    • Resource Reservation Protocol (RSVP)
      • Network Layer (Reserves network bandwidth and assigns priority to traffic)
what is a codec
What is a Codec?
  • A driver that converts from one format to another by compressing or uncompressing data.
    • Audio
      • G.711, G.722, G.723
    • Video
      • MPEG-4, Vivo H.263
protocols
Protocols
  • H.225 - call control protocol
    • Defines packet standards
  • Q.931 - digital subscriber signaling
    • Call signals at Network layer
protocols13
Protocols
  • H.245 - media control protocol
    • Provides end-to-end signaling for multimedia operation and signaling.
    • Determines Master and Slave
  • T.120 - Real time data conferencing protocol
protocols14
Protocols
  • H.235 – security
    • Authentication
    • Privacy (data encryption)
    • Key Exchange (RSA)
advantages
Advantages
  • Packet switched which allows all of the bandwidth to be used. Circuit switched results in gaps.
  • Usage cost by bypassing PTSN
  • Ability to merge real-time voice into other Internet applications
obstacles
Obstacles
  • Setup Cost
  • Greater Adherence to Standards
  • Ease of Administration
  • Greater Public Awareness
technical barriers
Technical Barriers
  • Reliability
  • Sound Quality (Limited Bandwidth)
  • Packet-switched connectionless network
potential problems
Potential Problems
  • Gateway Connection Ability (TEST!!!)
  • Must retain human voice characteristics
  • Latency (> 250ms)
  • Jitter
  • dropped packets (> 3%)
  • Passing of DTMF tones
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