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VoIP

VoIP. Voice over Internet Protocol. What is VoIP? Types of VoIP services? How does it Work? Benefits & Limitations?. VoIP. Voice communication transmitted over a digital/computer network Voice transmitted using the same protocols used on the Internet. VoIP= Voice over Internet Protocol.

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VoIP

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  1. VoIP Voice over Internet Protocol

  2. What is VoIP? Types of VoIP services? How does it Work? Benefits & Limitations? VoIP

  3. Voice communication transmitted over a digital/computer network Voice transmitted using the same protocols used on the Internet VoIP=Voice over Internet Protocol

  4. VoIP is an evolution of the old reliable plain old telephone service (POTS) Switch board operators Mechanical switches Digital switches (70s & 80s) IP telephony POTS, PSTN & VoIP - Analog vs. Digital

  5. PSTN – Public Switched Telephone Network (the worldwide telephone network) 4 Elements of the PSTN Customer Premises Equipment Access System Transport Core Signaling VoIP vs. PSTN

  6. PSTN – 4 Elements Fig. 6-1 (Panko 2004)

  7. VoIP - A method for converting analog audio signals to digital data to betransmitted using IP VoIP does not rely on the PSTN infrastructure but will interface with it VoIP vs. PSTN

  8. CARRIER NETWORKS used by PSTN to improve bandwidth efficiency PRIVATE NETWORKS used by large corporation to bypass PSTN (reduce cost) PUBLIC INTERNET used by consumer and small business markets Why? – usually because of cost Who uses VoIP?

  9. PSTN based on circuit switching VoIP uses packet switching Circuit Switching vs. Packet Switching

  10. 2-way connection with reserved capacity 2 systems wanting to communicate establish a circuit before they transmit any information That circuit remains open for the duration of the exchange Circuit Switching - PSTN

  11. Works well for voice transmission Voice traffic fairly constant (someone talking most of the time) Not good for data transmission Data traffic has short high speed bursts of data separated by long silences Reserved capacity of circuit wasteful Circuit Switching - PSTN

  12. No dedicated end-to-end connection Breaks voice conversation into pieces Transmits the pieces (pieces find their own way through the network) Reassembles the pieces back into voice conversation Packet Switching

  13. Fig. 2-1 (Doherty 2006) http://www.pbs.org/opb/nerds2.0.1/geek_glossary/packet_switching_flash.html

  14. Signaling (how communication is handled between switches and phones) VoIP uses a TERMINAL ADAPTER connects home handset to broadband Internet Acts as a translator (converts analog to digital) Terminal Adapter to SOFTSWITCH digital messages received by broadband phone service provider’s softswitch Softswitch is a specialized database/mapping program. The Softswitch knows where endpoints are on the network, what number is associate with that endpoint, and the current IP address assigned to that endpoint. - routes calls How does VoIP work?

  15. Fig. 2-4 (Doherty 2006)

  16. Fig. 2-3 (Doherty 2006)

  17. ATA – analog telephone adapterconnects a standard phone to computer/Internet connection for use with VoIP IP PHONES – has technology needed to encode voice for digital transfer and to send and receive packets over IP (Built-in NIC, RJ-45 adapter) (also WiFi wireless Internet phones) COMPUTER-to-COMPUTER – software (softphone), microphone, speakers and Internet connection. Free or low-cost Types of VoIP Service

  18. Human voice = analog sound Digital telephony Human voice converted to digital stream by a transmitter (re-created on receiving end) Analog-to-Digital conversion accomplished by SAMPLING SAMPLING Analog sound wave measured thousands of times per second Voltage levels converted to digital bytes VoIP conversation

  19. Voice PacketizationFig. 2-6 (Doherty 2006)

  20. VoIP uses IP (based on IP address not phone number) IP is not a reliable protocol (no error correction) Not feasible to correct errors by retransmitting data (this delay would cause jitter) If packet lost – receiver replays previous packet’s sound or interpolates based on data of earlier and later packets UDP – User Datagram Protocol RTP – Real Time Protocol (contains sequence #’s and time stamps get things in order) UDP & RTP – for IP telephony transport

  21. With VoIP – many different types of hardware and software need to communicate(any combination of analog, softphone or IP phone, ATAs (to handle digital to analog conversion), and softswitches (to map calls) ). Several protocols currently used (for signaling (supervision)) H.323 (complex – designed for video conferencing) SIP – Session Initiation Protocol (more streamlined – designed specifically for VoIP) MGCP – Media Gateway Control Protocol (focused on endpoint control (call waiting,etc)) Other protocols used…

  22. Efficiency Cost Flexibility VoIP available anywhere there is an Internet connection Benefits of VoIP

  23. Limitations to 911 services (ex: WiFi Internet phone not compatible with E911 – routed instead to emergency call center) Power with VoIP phones Terminal adapter provides power to your handset Terminal adapters plugged into electrical outlet Limitations of VoIP

  24. Services

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