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Voice Over IP (VoIP)
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Voice Over IP (VoIP)

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  • MOS- Mean Opinion Score, a measure of voice quality score, each codecs has its own bandwidth requirements, VoIP normal delay is 100ms, so 3.5 is a good quality achievement


  • 1. Voice over IPVoice over IP Habib UllahHabib Ullah 12-MS-CSc-1212-MS-CSc-12
  • 2. Contents  Abstract  What isVoIP  HowVoIP works  VoIP Architecture  Components  Pros & Cons  Summary
  • 3. Abstract  Voice over Internet Protocol (VoIP) is a technology that enables one to make and receive phone calls through the Internet instead of using the traditional analogy PSTN (Public Switched Telephone Network) lines.
  • 4. What is VoIP?  VoIP is packetisation and transport of classic public switched telephone system audio over an IP network.  It allows 2-way voice transmission over broadband connection.  It is also called IP telephony, internet telephony, voice over broadband, broadband telephony.
  • 5. PSTN vs. INTERNET PSTN  Voice network use circuit switching.  Dedicated path between calling and called party.  Bandwidth reserved in advance.  Cost is based on distance and time. INTERNET  Data network use packet switching.  No dedicated path between sender and receiver.  It acquires and releases bandwidth, as it needed.  Cost is not based on distance and time.
  • 6. PBX Yesterday’s Networks Circuit Switched Networks (Voice) CO PBX CO CO Packet Switched Networks (Data) Router Router Router Router Router • Separated networks • Separated applications/services
  • 7. PBX IP Phone Converged Network PSTN CO Gateway Router Router Router Router • Converged network • Separated or integrated applications PBX IP Phone
  • 8. VoIP – How does it work?  Converting the voice signal  ADC (analog to digital)  DAC (digital to analog) Voice (source) - - ADC - - - Internet - - - DAC - -Voice (dest)  Transmission of voice traffic in packets
  • 9. VoIP – How does it work?  The 1-2-3s of VoIP  1. Compression – voice is compressed typically with one of the following codecs, G7.11 64k, G7.29AB 8k, G723.1 6.3k  2. Encapsulation – the digitized voice is wrapped in an IP packet  3. Routing – the voice packet is routed thru the network to its final destination
  • 10. LT S©Telcordia Technologies, Inc. Slide 10 IP Network Multimedia PC Multimedia PC Initially, PC to PC voice calls over the Internet VoIP Architecture? PSTN (DC) Gateway PSTN (NY) Gateway Public Switched Telephone Network Gateways allow PCs to also reach phones …or phones to reach phones
  • 11. Components  VoIP Protocols  VoIP Gateway  VoIP Codecs
  • 12. VoIP Network Model SIP RTP, RTCP, RTSP Transport Layer (UDP, TCP) Network Layer (IP, IP Multicast) Data Link Layer Physical Layer
  • 13. PURC IP Protocol LayeringIP Protocol Layering Physical Transport (e.g, Cable Modem) IP (Internet Protocol) TCP UDP Applications (e.g., email, web pages) Email Data (1000 bytes)TCP Header (20 bytes) IP Header (20 bytes) A Typical IP Datagram
  • 14. VoIP SIP
  • 15. VoIP Gateway  A VoIP gateway is a gateway device that uses Internet Protocols to transmit and receive voice communications (VoIP).
  • 16. VoIP Codecs  Codecs are used to convert an analog voice signal to digitally encoded version. Codecs vary in the sound quality, the bandwidth required, the computational requirements, etc.
  • 17. Do Companies Want VoIP? 76% Will!76% Will! Unsure 4% Not at all likely 4% Not very likely 16% Likely 28% Very likely 32% Extremely likely 16% Network World asked 500 readers to assess whether they would consider using voice over IP:
  • 18. Key Business Drivers for LAN-Based Telephony and VoIP 81%81% 59%59% 38%38% 26%26% 0 50 100 Save MoneySave Money Better Utilization of BandwidthBetter Utilization of Bandwidth Support MultimediaSupport Multimedia Improve Network ManagementImprove Network Management
  • 19. Security Risks  AsVoIP uses the Internet, for example, it is vulnerable to the same type as security risks  Hacking  Denial of service  Eavesdropping
  • 20. Summary
  • 21. Questions?