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VoIP—Voice over Internet Protocol

VoIP—Voice over Internet Protocol. EE290F Spring 2004 Xiaoxue Zhao. Content. PSTN-Public Switch Telephone Network Packet-Switched Network Comparison between PSTN and IP Network VoIP Standards VoIP Services QoS—Quality of Service. PSTN—Components . Access Lines (Local Loops)

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VoIP—Voice over Internet Protocol

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  1. VoIP—Voice over Internet Protocol EE290F Spring 2004 Xiaoxue Zhao

  2. Content • PSTN-Public Switch Telephone Network • Packet-Switched Network • Comparison between PSTN and IP Network • VoIP Standards • VoIP Services • QoS—Quality of Service

  3. PSTN—Components • Access Lines (Local Loops) Connects customer premises to the local voice switch • Switches Connect access line to each other • Trunks Connects voice switches to each other • PBX—Private Branch Exchange • Signaling—Connectionless PSTN Used for basic call set up, management, tear down and enhanced call features etc.

  4. PSTN—Structure Voice Channel Multiplexing Access lines Trunk Network CO Switch CO Switch PBX Signaling Network Business customers Residential customers

  5. Connection Establishment Information Transfer Connection Release Connection-Oriented Connectionless PSTN—Features • Connection-Oriented, Circuit-Switched • Guaranteed Bandwidth “All the bandwidth all the time.” • Stable Delays

  6. Application Presentation Application Services Session Transport Transport (TCP) Network IP Data Link Network Access Physical Packet-Switched Network • Packet—Unit of data containing the network address information • Network Layers • “Best effort”

  7. Virtual Circuits

  8. Comparison

  9. Packetizing Voice

  10. Why VoIP? • Cost Reduction • Simplicity • Advanced Applications • Web-enabled call centers • Collaborative white boarding • Remote telecommuting

  11. Application Layer Transport Layer Network Layer Network interface Layer VoIP Standards • H.323—ITU-T • Session Initialization Protocol (SIP)—IETF

  12. H.323 • Packet-Based Multimedia Communications Systems • H.323 Architecture • H.323 for IP Telephony

  13. H.323 multipoint control unit (MCU) H.323 terminal H.323 gatekeeper H.323 gateway H.323 terminal H.323 terminal N-ISDN B-ISDN QoS LAN PSTN V.70 terminal H.324 terminal Speech terminal H.322 terminal Speech terminal H.320 terminal H.321 terminal H.323 Architecture LAN

  14. H.323 for IP Telephony

  15. SIP • Proposed by Internet Engineering Task Force (IETF) • Application layer control protocol • Borrow design and architecture from the Hypertext Transfer Protocol (HTTP)

  16. VoIP Services • Self-provided Customer • Independent of Internet access • Provided by broadband access service provider • Corporate Internal Use on Business LAN / WAN • Carrier Internal Use

  17. Call setup and Call data Internet Address Info Self-Provided Customer • IP connection • Voice-enabled device • Examples: Skype, MSN Address Info

  18. PSTN Analogue phone PSTN signaling PSTN call Gateway Signaling and Call setup Call data Internet SIP Server Signaling and Call setup SIP phone Independent of Internet Access • Customer in agreement with IP telephony company, independent of ISP • Uses gateway to connect to PSTN • Calls can be made to either VoIP users or PSTN users • IP connection and Voice-enabled device • Examples: Vonage, Packet8, Net2Phone

  19. Call data ATA Access provider network Signaling and call setup ATA SIP Server for both users Signaling and call setup Provided by Broadband Access Service Provider • Customer in agreement with IP telephony company with is also ISP • Uses gateway to connect to PSTN • Provider is in control of the network so offer quality guarantees • Analogue terminal adapters are provided • Example: Yahoo!BB (Japan)

  20. PSTN Ethernet phone PSTN Gateway Ethernet LAN Converter Gateway Analogue phone IP Router WAN or Internet Gatekeeper PC based virtual phone Corporate Internal Use on Business LAN / WAN • No service provider • In-house telephony on LAN or WAN • Services are those of a full-featured PBX

  21. Analogue phone H.323 Gateway Call data Carrier Network Signaling and set up H.323 Gateway Carrier SoftSwitch Signaling and set up Analogue phone Carrier Internal Use • Softswitch instead of circuit switch, including H.323 gatekeeper or SIP server • Most based on H.323 • Mostly in international calls

  22. QoS—Quality of Service QoS Parameters • Bandwidth • Delay • Jitter (Delay Variation) • Information Loss • Reliability • Security

  23. References • IP Telephony Walter J. Goralski and Matthew C. Kolon McGraw-Hill • Final Report for the European Commission—IP Voice and Associated Convergent Services

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