VOIP by wulinqing


(Voice Over Internet Protocol)

          CDA 4527
          Fall 2006
– also called IP Telephony, Internet telephony,
  Broadband telephony, Broadband Phone and Voice
  over Broadband
– the routing of voice conversations over the Internet or
  through any other IP-based network

                Cisco IP Phone 7941G
                  Big Picture
• Modes of operation:
  –   PC to PC
  –   PC to phone
  –   Phone to PC
  –   Phone to Phone
• Traffic go through Packet
  Switched Network instead of   From Wikipedia, the free encyclopedia

  Public Switched Telephone
  Network (PSTN)
                    Why VOIP?
• Much cheaper
• Rich functionalities
  – Free phone numbers for use with VoIP are available in the USA,
    UK and other countries.
  – 3-way calling, call forwarding, automatic redial, and caller ID…
  – Integrated with data, video communication

• Mobility
  – Incoming phone calls can be automatically routed to your VoIP
    phone, regardless of where you are connected to the network
• Quality of Service (QoS)
  – Internet provides best of service
  – No guarantee for latency, jitter…
• Need Internet connection
  – Home broadband is not reliable
• Power issue
  – VOIP phone, Cable Modem/DSL, Computer
• Security
  – Most unencrypted
  – VOIP spam challenges
• Integration into global telephone number
• Emergency call availability & functionality
  – Power, Internet connection
  – Call routing, location service

• Deal with Jitter
   – Smoothed by playback buffer
• Bandwidth
   – 64 kbps or less
   – Depends on codec and use of silence supression

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