VoIP (ppt)


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VoIP (ppt)

  1. 1. Packet Voice Protocols and VoIP Fall 2002 – Computer Networking Seyed Ali Ahmadi
  2. 2. VoIP Technology <ul><li>Identify the different generations of VoIP </li></ul><ul><li>Explain the basic operations of a VoIP Gateway </li></ul><ul><li>Describe an ITSP business case </li></ul><ul><li>How gateway architecture affects service providers </li></ul>
  3. 3. VoIP technology <ul><li>Recent Evolution of packet voice and VoIP </li></ul><ul><li>VoIP technology </li></ul><ul><li>VoIP evolution scenarios </li></ul>
  4. 4. 1- Recent Evolutions in VoIP <ul><li>Describe existing voice over data architectures and name their predecessors </li></ul><ul><li>How an ITSP work ? </li></ul><ul><li>Characteristics of an Internet call </li></ul><ul><li>Advantages and Disadvantages of ITSP </li></ul>
  5. 9. VoFR and VoATM Are Similar to VoIP <ul><li>Voice is sent as packets intermingled with other traffic types </li></ul><ul><li>Voice may be compressed for efficiency </li></ul><ul><li>Delay and Delay variation are issues </li></ul><ul><li>Priority for voice traffic is required for best performance </li></ul>
  6. 11. VoIP Generations <ul><li>PC-to-PC </li></ul><ul><li>PC-to-Phone </li></ul><ul><li>Phone-to-Phone </li></ul><ul><li>Traditional PBX migration to VoIP </li></ul><ul><li>IP PBX </li></ul>
  7. 12. ISTP Technology <ul><li>Different Types of IP calls </li></ul><ul><li>How ITSP deploy gateways </li></ul>
  8. 17. Generic Gateway
  9. 20. Dedicated Infrastructure for ITSP <ul><li>Eliminate dependence on performance of the Internet </li></ul><ul><li>Carries strictly voice traffic or Prioritize voice over data </li></ul><ul><li>Offers cheap long distance as initial service </li></ul><ul><li>Positioned as enhanced service provider from regulatory point of view </li></ul>
  10. 22. <ul><li>Place gateways in countries with high international tariffs or high calling volumes. </li></ul><ul><li>These Gateways support standard end user business interfaces to PSTN </li></ul><ul><ul><li>T1 </li></ul></ul><ul><ul><li>E1 </li></ul></ul><ul><ul><li>Analog </li></ul></ul><ul><ul><li>ISDN </li></ul></ul>
  11. 26. Regulatory Status <ul><li>Most of the world has taken a hands-off position in regulating the enhanced service providers </li></ul><ul><li>In genera ITSPs have mostly positioned them as ISPs </li></ul><ul><li>As a result, ITSPs typically do not pay carrier fees such as connection, access or settlement fees </li></ul><ul><li>IP telephony is regulated in some countries and illegal in some others. </li></ul>
  12. 28. 2- VoIP Protocols and Technology
  13. 29. <ul><li>A little on history </li></ul><ul><li>Communication pattern shift from PSTN to VoIP </li></ul><ul><li>Why VoIP? </li></ul><ul><ul><li>Cost saving </li></ul></ul><ul><ul><li>Open standards and Multivendor interoperability </li></ul></ul><ul><ul><li>Integrated voice and Data network </li></ul></ul>
  14. 30. VoIP Protocols <ul><li>H.323 </li></ul><ul><li>Media Gateway Control Protocol (MGCP) </li></ul><ul><li>Session Initiation Protocol (SIP) </li></ul><ul><li>H.248–Media Gateway Control (MEGACO) </li></ul>
  15. 31. Great Voice Myth <ul><li>“ In order to have a reliable and robust Voice network, there should be one and only one protocol for each function in packet switch network.” </li></ul><ul><li>This is not how we are actually doing it now!! </li></ul><ul><li>The VoIP networks of today and tomorrow will be constructed using the protocols and applications that best fit the associated technology and business requirements. </li></ul>
  16. 32. Protocol Terminology <ul><li>ITU: International Telecommunication Union </li></ul><ul><li>IETF: Internet Engineering Task Force </li></ul>
  17. 33. Protocol Terminology <ul><li>H.248 Gateway Control Protocol </li></ul><ul><ul><li>Collaboration between ITU & IETF </li></ul></ul><ul><ul><li>Also referred to as IETF RFC 2885 (MEGACO) </li></ul></ul>
  18. 34. Protocol Terminology <ul><li>H.323 </li></ul><ul><ul><li>ITU recommends for “ Packet based Multimedia communication systems”. </li></ul></ul><ul><ul><li>Most common VoIP protocol </li></ul></ul><ul><ul><li>Distributed Architecture </li></ul></ul>
  19. 35. Protocol Terminology <ul><li>SIP: Session Initiation Protocol </li></ul><ul><ul><li>IETF RFC 2543 </li></ul></ul><ul><ul><li>Distributed Architecture </li></ul></ul><ul><li>Real-time Transport Protocol – RTP </li></ul><ul><ul><li>A transport protocol for real-time application </li></ul></ul><ul><ul><li>IETF RFC 1889 </li></ul></ul><ul><ul><li>Provides transport for audio/media of VoIP communication </li></ul></ul><ul><ul><li>Used by All of VoIP signaling protocols </li></ul></ul>
  20. 36. Protocol Terminology <ul><li>MGCP Media Gateway Control Protocol </li></ul><ul><ul><li>IETF RFC 2075 </li></ul></ul><ul><ul><li>Centralized Architecture for Multimedia applications such as VoIP </li></ul></ul>
  21. 39. Distributed vs. Centralized
  22. 40. Centralized Architecture <ul><li>Mostly used in older networks </li></ul><ul><li>Worked well for basic telephony services </li></ul><ul><li>Trade off between easy management and endpoint innovation </li></ul><ul><li>Associated with MGCP and H.248 </li></ul><ul><li>Intelligence focused in centralized Gateway unit (media agent) </li></ul><ul><li>Endpoints are relatively or completely dumb. </li></ul>
  23. 41. Centralized Architecture Pros & Cons <ul><li>Centralizes management, provisioning and call control </li></ul><ul><li>Simplifies call flow for legacy voice features </li></ul><ul><li>Stifles innovation of endpoint features </li></ul><ul><li>Limitations in building VoIP networks beyond legacy voice features </li></ul>
  24. 42. Distributed Architecture <ul><li>Associated with H.323 and SIP protocol </li></ul><ul><li>Allows Network Intelligence to be distributed between endpoints and control devices. </li></ul><ul><li>Intelligence: </li></ul><ul><ul><li>Call state </li></ul></ul><ul><ul><li>Calling features </li></ul></ul><ul><ul><li>Calling routines </li></ul></ul><ul><ul><li>… any aspect of call handling </li></ul></ul>
  25. 43. Distributed Architecture Pros & Cons <ul><li>More flexible </li></ul><ul><li>VoIP is treated like any other distributed IP application </li></ul><ul><li>Well understood by engineers who design and run IP data networks </li></ul><ul><li>More complex than the Centralized Architecture </li></ul>
  26. 44. H.323 <ul><li>Originally designed as a transport protocol for MM Apps. in LAN </li></ul><ul><li>Still used for Video Conferencing </li></ul><ul><li>Most widely used VoIP signaling and call control </li></ul><ul><li>Umbrella Protocol: </li></ul><ul><ul><li>All aspects of call transmission </li></ul></ul><ul><ul><li>From call establishment to capabilities exchange to network resources </li></ul></ul>
  27. 45. H.323 <ul><li>Defines: </li></ul><ul><ul><li>RAS </li></ul></ul><ul><ul><ul><li>Registration </li></ul></ul></ul><ul><ul><ul><li>Admission </li></ul></ul></ul><ul><ul><ul><li>Status </li></ul></ul></ul><ul><ul><li>H.225 for call set-up </li></ul></ul><ul><ul><li>H.245 for capabilities exchange </li></ul></ul>