The limitations of the circuit-switching techniques of conventional telephony may now be overcome through integration with IP technologies. Internet Telephony is a powerful and economical communication option by combination of the telephone networks and data networks. IP telephony used to send audio, video, fax etc between two or more users in real time via packet switched network. The main motivation of IP telephony is Cost savings and ease of developing and integrating new services. Four type of IP telephony according to terminal equipment and types of network is PC to PC, Phone to Phone, PC to Phone, Phone to PC. There are many standard based on IP telephony like SIP (session intonation protocol) and H.323 and many more.H.323 is currently the most widely supported IP telephony signaling protocol. Terminals, gateways, gatekeepers, multipoint control units are the basic component of H.323 standard. Audio CODECs, video CODECs, H.225 registration, admission, and status (RAS), H.225 call signaling, H.245 control signaling, real-time transfer protocol (RTP), real-time control protocol (RTCP) are the protocol used in H.323 for IP telephony
WHAT IS H.323
PROTOCOL SPECIFED BY H.323
H.323 CALL ESTABLISHMENT
H.323 CONTROL SIGNALING FLOW
H.323 MEDIA STREAM & MEDIA CONTROL FLOW
H.323 CALL RELEASE
Internet telephony uses the Internet protocol to send audio, video and data between two or more users in the real time.
IP telephony is the integration and convergence of voice and data networks, services, and applications.
The main motivation of development of IP Telephony is the cost saving & integrating new services.
Vocaltec introduced the first Internet telephony software product in early 1995. Running a multimedia PC, the Vocaltec Internet Phone.
In 1996, Vocaltec with Intel Company announced to produce the first IP telephony gateway.
Different Types Of IP Telephony
PC to PC
Phone-to-phone over IP
PC to PC
Phone-to-phone over IP using Gateways
Phone-to-phone over IP using Adapter Boxes
PC-to-Phone or Phone-to-PC
Different type of IP telephony Standard
Session initiation protocol (SIP)
Media gateway to media controller protocol (MGCP)
What is H.323
The H.323 standard for the transmission of real-time audio, video, and data communications over packet-based networks based on IP telephony.
H.323 is a standard produced by the ITU-T Study Group 16.
Currently the most widely-supported IP telephony signaling protocol.
Multipoint Control Units (MCUs)
H.323 terminal can either be a personal computer or a stand-alone device, running an H.323 and the multimedia applications.
An H.323 gateway provides connectivity between an H.323 network and a non-H.323 network.
Multipoint Control Units:
MCUs provide support for conferences of three or more H.323 terminals. All terminals participating in the conference establish a connection with the MCU.
Protocols Specified by H.323
H.225 registration, admission, and status (RAS)
H .225 call signaling
H.245 control signaling
real-time transfer protocol (RTP)
real-time control protocol (RTCP)
H .225 call signaling
H.225 call signaling is used to set up connections between H.323 endpoints over which the real-time data can be transported.
Two types :
Direct call signaling
Gateway routed call signaling
H.245 Control Signaling
Logical Channel Signaling
Real-Time Transport Protocol
Real-time transport protocol (RTP) provides end-to-end delivery services of real time audio and video.
RTP is used to transport data via the user datagram protocol
Real-Time Control Protocol (RTCP)
RTCP provides control services for RTP.
Internet telephony is cost savings and integrating new services.
Internet Telephony is a powerful and economical communication options by combination of the telephone networks and data networks.
Many public telecommunication operators are establishing their own IP telephony services, and using IP-based networks as alternative transmission platforms.