A Presentation on H.323
Deepak Bote

 Bill Clinton was re-elected.
 Dolly, the cloned sheep, was born.

Prince Charles and Diana were divorced…
 Emergence of VoIP & Internet Telephony
We are interested in the last one!

 VoIP products were proprietary.
 Hence incompatible.
 A standard for interoperability
 H.323 v1 was already existing for
LANs.
 V2 was developed to solve the incompatibility issue.

 Standard recommended by ITU-T
 Defines real-time MM communications over packet based networks.
 Collection of Standards.
 H.323 belongs to the H.32x class of standards for videoconferencing applications.

 Terminals (what people see/hear)

Gateways (control and ‘routing’ )
 conference capabilities )
 Gatekeepers (access to other environments)
D
P
E
N
I
O
T
S

 H.323 client endpoints
 They could be:
 Multimedia PCs
 Any stand-alone device
 A simple telephone
 Expectation by H.323:
 Must support audio communication.
 Video, data support optional

 Optional Component of H.323 implementation.
 Used as interface between different networks e.g. LAN & PSTN
 Functions:
 Data format translation
 Audio/video codec translation
 Call setup, termination from both sides of the network

 MCUs are also optional in a H.323 implementation
 Needed only when multiparty conferences are desired
 Functions:
 Provides capability of video-conferencing with more than one party.
 Acts as a co-ordinator of multiparty conferences


“Brains” of a H.323 network
 Expectation by H.323:
 Address translation
 Admissions Control
 Bandwidth Control
 Zone Management
 Routing Capabilities

Zone B
Gatekeeper
The Internet
Gateway
Zone A
Gatekeeper

MCU
Router
Gatekeeper
Gateway Phone
H.323 terminal
H.323 terminal
Gateway
ISDN videophone


H.323 recommendation is a “framework” document that describes how the various pieces fit together
 H.225.0 defines the call signaling between endpoints and the Gatekeeper
 RTP/RTCP (RFC 3550) is used to transmit media such as audio and video over IP networks
 H.225.0 define the procedures and protocol for communication within and between Peer Elements
 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

 H.450.x is a series of supplementary service protocols
 H.460.x is a series of version-independent extensions to the base H.323 protocol
 T.120 specifies how to do data conferencing
 T.38 defines how to relay fax signals
 V.150.1 defines how to relay modem signals
 H.235 defines security within H.323 systems

 Audio:
 G.711 (popular codec for telephone n/ws)
 G.723.1 – more efficient
 Video
 H.261 codec (for channels with bandwidths p*64 kb/s)
 H.263 codec (for low bit rate transmission without loss of quality )

Data
Applications
Media Control Terminal Control and Management
V.150
T.120
T.38
Audio
Codecs
G.711
G.723.1
G.729
..
Video
Codecs
H.261
H.263
H.264
..
RTCP
H.225.0
Call
Signaling
H.245
H.225.0
RAS
RTP
UDP TCP TCP/UDP UDP
IP
TCP/UDP TCP UDP

H.323 Application
RAS
H.245
H.225.0
Call Signaling
Packet Network
RTP /
RTCP

H.323 Call Setup and Tear Down

 Users want mobility “Internet Phone
Numbers” that follow them anywhere
 Enhancements for billing
 Enhancements to fax
 More interoperability

 H.323 is a protocol that leverages the strength of the packet-switched protocols from the IETF
 H.323 offers excellent integration with the PSTN
 H.323 enables voice, video, and data conferencing
 H.323 provides a solid foundation for new services and the continued growth of Multimedia over IP

 www.h323forum.org
 http://www.packetizer.com/voip/h323/
 Intel Tutorial site

 Defined in H.225.0
 Allows an endpoint to request authorization to place or accept a call
 Allows a Gatekeeper to control access to and from devices under its control
 Allows a Gatekeeper to communicate the address of other endpoints
 Allows two Gatekeepers to easily exchange addressing information