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Voice Over IP

Voice Over IP. CS158B Project By Shing Chau Jerry Ko Ying Li. Agenda. Introduction Economics of VoIP VoIP and OSI model comparison H.323 vs. SIP RSVP & RTP Demonstration. Introduction. VoIP Transmission of voice traffic in packets

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Voice Over IP

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  1. Voice Over IP CS158B Project By Shing Chau Jerry Ko Ying Li

  2. Agenda • Introduction • Economics of VoIP • VoIP and OSI model comparison • H.323 vs. SIP • RSVP & RTP • Demonstration

  3. Introduction VoIP • Transmission of voice traffic in packets • Internet as the transmission medium • IP rather than by traditional circuit transmission • IP originally for data • adaptation to voice network • protocols (SIP, H.323, RSVP, RTCP, RTP)

  4. Economics of VoIP • Traditional TDM • Dedicated Circuit switched networks • Dedicated voice-only bandwidth • IP • Uses packet switched networks • Many Services, one network (voice, data) • Leverages existing data infrastructure • Flat monthly rate both long distance and local • Various configurations

  5. VoIP and OSI model Comparison

  6. Session Initiation • Three things takes place in a VoIP session: • Signaling • Encoding • Transmission • Two common protocols used: • H.323 – International Standard • Session Initiation Protocol (SIP)

  7. H.323

  8. H.323 vs. SIP

  9. How to send voice over RTP? Application collects the encoded data in chunks The audio chunk along with the RTP header form the RTP packet RTP header contains: Payload type (7 bits) Sequence number (16 bits) Timestamp field (32 bits) Synchronization source identifier field (32 bits) RTP (Real-Time Protocol)

  10. Why a guaranteed QoS is needed? Voice and Video applications traffic can be transmitted continuously It requires a guaranteed QoS, in terms of minimum available bandwidth or maximum delay, over the entire path of traffic How to make the resource reservations? RSVP(Resource Reservation Protocol)

  11. Path messages contain: • Previous hop address • A session identifier • A sender template (the sender’s IP address and port number ) • A sender T Spec (maximum data rate, maximum delay, etc)

  12. Reservation messages contain: • Reservation Style • Flow Spec • Filter Spec

  13. Summary • Rsession Initiation • SIP (SNMP): simple • H.323 (CMIP): complex • QoS • RSVP • Voice Transmission • RTP

  14. Invite 200 OK RTP 100 Trying 180 Ringing ACK SIP Call Flow

  15. TCP connection H.225 Messages (Setup) H.225 (CallProceeding, Alerting) H.225 (Connect) TCP connection Terminal Capability Set MasterSlaveDetermination OpenLogicalChanel OpenLogicalChanelAck RTP stream RTP stream RTCP stream H.323 Call Flow

  16. Reference • Voice Over IP -by Uyless Black, a guide to Internet voice communications, covers many protocols • Computer Networking-chapter 7 Multimedia Networking • Course offering -EE284 Convergent Voice and Data Networks, multimedia in data networks, QoS, Coding, Signaling, and Inter-working

  17. Thank You!

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