Important events of 1996!! n Bill Clinton was re-elected. n Dolly, the cloned sheep, was born. was born. n Prince Charles and Diana were divorced… n Emergence of VoIP & Internet Telephony We are interested in the last one!
What about H.323??? n VoIP products were proprietary. n Hence incompatible. n A standard for interoperability n H.323 v1 was already existing for LANs. n V2 was developed to solve the incompatibility issue.
What exactly is H.323? n Standard recommended by ITU-T n Defines real-time MM communications over packet based networks. n Collection of Standards. n H.323 belongs to the H.32x class of standards for videoconferencing applications.
H.323 – A Closer Look n Terminals (what people see/hear) n Gateways (control and ‘routing’ ) n Multipoint Control Units (provides conference capabilities ) n Gatekeepers (access to other environments) ENDPOINTSENDPOINTS
Terminals n H.323 client endpoints n They could be: u Multimedia PCs u Any stand-alone device u A simple telephone n Expectation by H.323: u Must support audio communication. u Video, data support optional
Gateways n Optional Component of H.323 implementation. n Used as interface between different networks e.g. LAN & PSTN n Functions: u Data format translation u Audio/video codec translation u Call setup, termination from both sides of the network
Multipoint Control Units n MCUs are also optional in a H.323 implementation n Needed only when multiparty conferences are desired n Functions: u Provides capability of video-conferencing with more than one party. u Acts as a co-ordinator of multiparty conferences
Gatekeepers n “Brains” of a H.323 network n Expectation by H.323: u Address translation u Admissions Control u Bandwidth Control u Zone Management u Routing Capabilities
Gatekeeper Gateway Zone B Zone A The Internet Gatekeeper Zones Gatekeeper Zones
The Protocols (cont) n H.323 recommendation is a “framework” document that describes how the various pieces fit together n H.225.0 defines the call signaling between endpoints and the Gatekeeper n RTP/RTCP (RFC 3550) is used to transmit media such as audio and video over IP networks n H.225.0 define the procedures and protocol for communication within and between Peer Elements n H.245 is the protocol used to control establishment and closure of media channels within the context of a call and to perform conference control
The Protocols (cont) n H.450.x is a series of supplementary service protocols n H.460.x is a series of version-independent extensions to the base H.323 protocol n T.120 specifies how to do data conferencing n T.38 defines how to relay fax signals n V.150.1 defines how to relay modem signals n H.235 defines security within H.323 systems
n Audio: u G.711 (popular codec for telephone n/ws) u G.723.1 – more efficient n Video u H.261 codec (for channels with bandwidths p*64 kb/s) u H.263 codec (for low bit rate transmission without loss of quality ) The Protocols (cont)
Typical H.323 Stack H.323 IP UDP RTP RTCP TCP/UDPTCPUDP TCP Audio Codecs G.711 G.723.1 G.729.. Video Codecs H.261 H.263 H.264.. V.150T.120 TCP/UDP T.38 H.225.0 Call Signaling H.245 H.225.0 RAS Terminal Control and Management Data Applications Media Control Multimedia Applications, User Interface
Future n Users want mobility - “Internet Phone Numbers” that follow them anywhere n Enhancements for billing n Enhancements to fax n More interoperability
Concluding Remarks n H.323 is a protocol that leverages the strength of the packet-switched protocols from the IETF n H.323 offers excellent integration with the PSTN n H.323 enables voice, video, and data conferencing n H.323 provides a solid foundation for new services and the continued growth of Multimedia over IP
References n www.h323forum.org www.h323forum.org n http://www.packetizer.com/voip/h323/ http://www.packetizer.com/voip/h323/ n Intel Tutorial site
Registration, Admission, and Status - RAS n Defined in H.225.0 n Allows an endpoint to request authorization to place or accept a call n Allows a Gatekeeper to control access to and from devices under its control n Allows a Gatekeeper to communicate the address of other endpoints n Allows two Gatekeepers to easily exchange addressing information