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Voice Over IP

Voice Over IP. Presented By Jas Ahluwalia Tony Chen May 29, 2003. Introduction. Voice has been transmitted over PSTN (POTS) since 1878. U.S. Long-Distance Market is $100 billion a year $100 billion?!! Businesses and consumers wish to reduce this cost.

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Voice Over IP

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  1. Voice Over IP Presented By Jas Ahluwalia Tony Chen May 29, 2003

  2. Introduction • Voice has been transmitted over PSTN (POTS) since 1878. • U.S. Long-Distance Market is $100 billion a year • $100 billion?!! Businesses and consumers wish to reduce this cost. • Over the last decade the emergence of the internet has caused a significant investment in IP based networks • Can we use these IP based networks for voice?

  3. VoIP – Big Picture • User’s voice converted from analog to digital signal. • Digital signal is compressed. • Compressed signal is assembled into packets. • Packets transported over IP networks.

  4. Technical Issues • For good voice quality we need to ensure that latency does not exceed 200ms. • IP Networks have several sources of delay which increase latency

  5. Protocols • Uses Resource Reservation Protocol (RSVP) • Applications request resources from the network • Each hop conducts admission control decision for the request and sets up per-flow state. • Two Components • Resource Allocation (How much to reserve) • Packet Filters (what packets get to use these resources) • Uses the User Datagram Protocol (UDP) over IP • Avoids Acknowledgments for lost packets • Acknowledgements trigger retransmissions which increase network traffic and decrease Quality of Service (QoS) • Packets could come out of order though. What do we do?

  6. Protocols • Realtime Transport Protocol (RTP) • Used to support transport of real-time media • RTP packets contain: • Media information • Header provides information to receiver that allows reordering of out-of-sequence packets. • Several Companion protocols • Real Time Control Protocol (RTCP) • Provides QoS feedback to sending device. • Real Time Streaming Protocol (RTSP) • Used to control stored media devices

  7. Architecture • H.323 – provides foundation for audio, video, and data communications across IP Networks • Terminals • Device the user is using (phone, pc, etc.) • Gateways • Used for protocol conversion between IP and circuit-switched networks • Gatekeepers • Used for bandwidth management, address translation, and call control • Multipoint Control Unit (MCU) • Supports multicast conferences among three or more end points.

  8. Multipoint Control Unit Gatekeeper Packet Based Networks Terminal Gateway Architecture • H.323 Circuit Switched Networks

  9. Big Picture Again • Architecture: H.323 or MGCP • MGCP: Media Gateway Control Protocol • QoS: RSVP • Protocols: RTP over UDP over IP

  10. RTP over UDP over IP

  11. PSTN Vs. VoIP

  12. Current VoIP Implementations

  13. Coexistence • Telcordia’s Next Generation Network and Voice over Packet architecture (NGN/VOP) • Core Packet Network • Call Connection Agent • Signaling Gateway • Trunk gateway • Access gateway • Billing agent.

  14. Coexistence

  15. Veraz Networks • Provide Carrier Grade Solution for companies like AT&T, MCI, etc • MCI creates dedicated IP network for voice traffic termed “Engineered IP Network” • Benefits of Engineered IP Network: • A 20,000 Telephone Line Exchange costs $12-$14 Million • Exchanges are huge and require special housing (protection for fire, flooding, etc.) • Next Generation Solution cost $2-$3 million and is small (desktop size). • Call between LA and NY goes over several nodes in telephone sytem. • Only one Next Generation Solution is needed for same call.

  16. Veraz Networks • 2 part solution • Softswitch • Software brains of the system • Make/break connections, etc. • Media Gateway • Interface to existing telephone system • Interface to IP Network. • Veraz/Nexverse wish to bring about the same evolution that the computing world saw. • Smaller, more powerful, cheaper computers

  17. Conclusion • VoIP provides a cost effective solution • Can envision a wide array of applications that can complement VoIP • However, previous slide shows several issues that need to be resolved before widespread deployment.

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