Voice Over IP CS158B Project By Shing Chau Jerry Ko Ying Li Agenda
Introduction Economics of VoIP VoIP and OSI model compa rison H.323 vs. SIP RSVP & RTP Demonstration 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) 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 l ocal Various configurations VoIP and OSI model Comparison 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) H.323 H.323 vs. SIP H.323 SIP Origin ITU
IETF Transport Mostly TCP Mostly UDP Telephony Multimedia Emphasis
RTP (Real-Time Protocol) 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) RSVP (Resource Reservation Protocol) Why a guaranteed QoS is needed? Voice and Video applications traffic can be tra nsmitted continuously
It requires a guaranteed QoS, in terms of mini mum available bandwidth or maximum delay, over the entire path of traffic How to make the resource reserva tions? Path messages contain:
Previous hop address A session identifier A sender template (the senders IP address and port number ) A sender T Spec (maximum data rate, maximum delay, etc) Reservation messages contain:
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