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VOIP operates by transferring voice through IP packets over the Internet. This guide explains the workings of VOIP, its components, protocols like H.323, gateways, gatekeepers, and more. Explore the call setup process, SIP messages, and the evolution of VoIP technology.
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VOICE OVER INTERNET PROTOCOL UNDER THE GUIDANCE OF N. SRINIVASU SUBMITTED BY SHREETAM MOHANTY ROLL # EC200118010
INTRODUCTION What is VOIP ? Voice over Internet Protocol transfers voice through IP packets through the Internet. VoIP can use special hardware or a PC environment to achieve this purpose. How does VOIP works: Voice (source) - - ADC - - - - Internet - - - DAC - - Voice (dest)
PACKET FREQUENCY • Packet frequency as the number of packets containing voice samples which are sent per second • Components of H.323 • Terminals • Gateways • Gatekeepers
H.323 TERMINAL SUPPORTING OTHER PROTOCOLS • H.245 : allowing the usage of the channels. • Q.931: call signaling and setting up the call • RTP: carries voice packets • RAS: interacting with the gatekeeper
GATEWAYS • Interface between the PSTN and the Internet • Translator : H.225 to H.221 or audio to video
GATEKEEPERS • Controls the end points under its zone Function • Address Translation • Admissions Control • Call signaling • Call Authorization • Bandwidth Management
DEFINITIONS ZoneThe collection of a gatekeeper and the endpoints registered with it is called a zoneNetwork AddressFor each H.323 entity, a network address is assigned and this address uniquely identifies the H.323 entity on the network TSAP Identifier These TSAP identifiers allow multiplexing of several channels sharing the same network address
CALL SETUP IN H.323 Endpoint enters the call setup phaseDiscovering a gatekeeper which would take the management of that endpointThe capability exchange takes place between the endpoint and the gatekeeper Registration of the endpoint with its gatekeeper The call is established
SESSION INITIATION PROTOCOL (SIP) • It is an application layer control protocol for creating, modifying and terminating sessions with one or more participants
SIP MESSAGES • INVITE:for inviting a user to a call • BYE:for terminating a connection between the two end points • ACK:invitation for reliable exchange of messages • OPTIONS: for getting information about the capabilities of a call • REGISTER: gives information about the location of a user to the SIP registration server. • CANCEL: for terminating the search for a user
CONCLUSION • Like everything else, as the technology changes so At first, only a few companies like Cisco and Lucent offered VoIP services, but the large telecommunications carriers – such as AT&T and Sprint -- are catching on • VoIP is predominately used for personal instead of enterprise-wide use, but will the people who use it.