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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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Internet Telephony

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Internet telephony l.jpg

Internet Telephony


Ip telephony l.jpg

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).


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Voice Based Applications

  • Automated Attendants

  • Voice Prompting

  • Voice Messaging

  • Faxing, Fax Services, Fax Broadcast

  • UnPBX

  • Speech Recognition

  • Text to Speech


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Phone-To-Phone Connection


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PC-To-Phone Topology


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IP Telephony Components

  • Gateway

    • Bridge between Internet and PSTN

  • Gatekeeper

    • Billing

    • Directory services

    • Authentication

    • Bandwidth Control


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PC-To-Phone Connection


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Components

  • Endpoints (Terminals)

  • Miltipoint Control Units (MCUs)


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H.323 Protocol Stack


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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)


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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


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Protocols

  • H.225 - call control protocol

    • Defines packet standards

  • Q.931 - digital subscriber signaling

    • Call signals at Network layer


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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


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Protocols

  • H.235 – security

    • Authentication

    • Privacy (data encryption)

    • Key Exchange (RSA)


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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


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Obstacles

  • Setup Cost

  • Greater Adherence to Standards

  • Ease of Administration

  • Greater Public Awareness


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Technical Barriers

  • Reliability

  • Sound Quality (Limited Bandwidth)

  • Packet-switched connectionless network


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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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Any Questions???


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