Voice Over IP - SJSU Computer Science Department

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:

Reservation Style Flow Spec Filter Spec Summary Rsession Initiation SIP (SNMP): simple H.323 (CMIP): complex QoS

RSVP Voice Transmission RTP SIP Call Flow Invite 100 Trying 180 Ringing 200 OK ACK

RTP H.323 Call Flow 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 Reference Voice Over IP -by Uyless Black, a guide to Internet voice communications, covers many protocols

Computer Networking -chapter 7 Multi media Networking Course offering -EE284 Convergent Voice and Data Netw orks, multimedia in data networks, QoS , Coding, Signaling, and Inter-working Thank You!

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