A Presentation on H.323A Presentation on H.323

Deepak BoteDeepak Bote

Email, IM, blog…Email, IM, blog…

Important events of 1996!!Important events of 1996!!

Bill Clinton was re-elected.Bill Clinton was re-elected.

Dolly, the cloned sheep, Dolly, the cloned sheep, was born.was born.

Prince Charles and Diana were divorced…Prince Charles and Diana were divorced… Emergence of VoIP & Internet TelephonyEmergence of VoIP & Internet Telephony

We are interested in the last one!

What about H.323???What about H.323???

VoIP products were proprietary.VoIP products were proprietary. Hence incompatible.Hence incompatible. A standard for interoperabilityA standard for interoperability H.323 v1 was already existing for H.323 v1 was already existing for

LANs.LANs. V2 was developed to solve the V2 was developed to solve the

incompatibility issue.incompatibility issue.

What exactly is H.323?What exactly is H.323?

Standard recommended by ITU-TStandard recommended by ITU-T Defines real-time MM communications over Defines real-time MM communications over

packet based networks.packet based networks. Collection of Standards.Collection of Standards. H.323 belongs to the H.32x class of standards H.323 belongs to the H.32x class of standards

for videoconferencing applications.for videoconferencing applications.

H.323 – A Closer LookH.323 – A Closer Look Terminals (what people see/hear)Terminals (what people see/hear)

Gateways (control and ‘routing’ )Gateways (control and ‘routing’ )

Multipoint Control Units (provides Multipoint Control Units (provides conference capabilities )conference capabilities )

Gatekeepers (access to other Gatekeepers (access to other environments) environments)

E

N

D

P

O

I

N

T

S

TerminalsTerminals

H.323 client endpointsH.323 client endpoints They could be:They could be:

Multimedia PCsMultimedia PCs Any stand-alone deviceAny stand-alone device A simple telephoneA simple telephone

Expectation by H.323:Expectation by H.323: Must support audio communication.Must support audio communication. Video, data support optionalVideo, data support optional

GatewaysGateways Optional Component of H.323 Optional Component of H.323

implementation.implementation. Used as interface between different Used as interface between different

networks networks e.g. LAN & PSTNe.g. LAN & PSTN

Functions:Functions: Data format translationData format translation Audio/video codec translationAudio/video codec translation Call setup, termination from both sides of the Call setup, termination from both sides of the

networknetwork

Multipoint Control UnitsMultipoint Control Units

MCUs are also optional in a H.323 MCUs are also optional in a H.323 implementationimplementation

Needed only when multiparty conferences are Needed only when multiparty conferences are desireddesired

Functions:Functions: Provides capability of video-conferencing with more Provides capability of video-conferencing with more

than one party.than one party. Acts as a co-ordinator of multiparty conferencesActs as a co-ordinator of multiparty conferences

GatekeepersGatekeepers

““Brains” of a H.323 networkBrains” of a H.323 network Expectation by H.323:Expectation by H.323:

Address translationAddress translation Admissions ControlAdmissions Control Bandwidth ControlBandwidth Control Zone ManagementZone Management Routing CapabilitiesRouting Capabilities

Gatekeeper

Gatekeeper

Gateway

Zone B

Zone A

The Internet

Gatekeeper ZonesGatekeeper Zones

Router

H.323 terminal H.323 terminal ISDN videophone

Gateway

Gateway Phone

MCUGatekeeper

The Protocols!!The Protocols!!

The Protocols (cont)The Protocols (cont) H.323 recommendation is a “framework” document that H.323 recommendation is a “framework” document that

describes how the various pieces fit togetherdescribes how the various pieces fit together H.225.0 defines the call signaling between endpoints and H.225.0 defines the call signaling between endpoints and

the Gatekeeperthe Gatekeeper RTP/RTCP (RFC 3550) is used to transmit media such as RTP/RTCP (RFC 3550) is used to transmit media such as

audio and video over IP networksaudio and video over IP networks H.225.0 define the procedures and protocol for H.225.0 define the procedures and protocol for

communication within and between Peer Elementscommunication within and between Peer Elements H.245 is the protocol used to control establishment and H.245 is the protocol used to control establishment and

closure of media channels within the context of a call and to closure of media channels within the context of a call and to perform conference controlperform conference control

The Protocols (cont)The Protocols (cont) H.450.x is a series of supplementary service H.450.x is a series of supplementary service

protocolsprotocols H.460.x is a series of version-independent H.460.x is a series of version-independent

extensions to the base H.323 protocolextensions to the base H.323 protocol T.120 specifies how to do data conferencingT.120 specifies how to do data conferencing T.38 defines how to relay fax signalsT.38 defines how to relay fax signals V.150.1 defines how to relay modem signalsV.150.1 defines how to relay modem signals H.235 defines security within H.323 systemsH.235 defines security within H.323 systems

Audio: Audio: G.711 (popular codec for telephone n/ws)G.711 (popular codec for telephone n/ws) G.723.1 – more efficientG.723.1 – more efficient

VideoVideo H.261 codec (for channels with bandwidths H.261 codec (for channels with bandwidths

p*64 kb/s)p*64 kb/s) H.263 codec (for low bit rate transmission H.263 codec (for low bit rate transmission

without loss of quality )without loss of quality )

The Protocols (cont)The Protocols (cont)

Typical H.323 StackTypical H.323 Stack

H.323

IP

UDP

RTP

RTCP

TCP/UDP TCP UDPUDP TCP

AudioCodecsG.711

G.723.1G.729

..

VideoCodecsH.261H.263H.264

..V.150 T.120

TCP/UDP

T.38H.225.0

CallSignaling

H.245 H.225.0RAS

Terminal Control and ManagementDataApplications Media Control

Multimedia Applications, User Interface

An H.323 StackAn H.323 Stack

RAS RTP / RTCP

Packet Network

H.323 Application

H.245

H.225.0Call Signaling

H.323 Call Setup and Tear Down

FutureFuture

Users want mobility - Users want mobility - “Internet Phone “Internet Phone Numbers” that follow them anywhereNumbers” that follow them anywhere

Enhancements for billingEnhancements for billing Enhancements to faxEnhancements to fax More interoperabilityMore interoperability

Concluding RemarksConcluding Remarks H.323 is a protocol that leverages the strength of H.323 is a protocol that leverages the strength of

the packet-switched protocols from the IETFthe packet-switched protocols from the IETF H.323 offers excellent integration with the PSTNH.323 offers excellent integration with the PSTN H.323 enables voice, video, H.323 enables voice, video, and and data conferencingdata conferencing H.323 provides a solid foundation for new H.323 provides a solid foundation for new

services and the continued growth of Multimedia services and the continued growth of Multimedia over IPover IP

ReferencesReferences

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

Registration, Admission, and Registration, Admission, and Status - RASStatus - RAS Defined in H.225.0Defined in H.225.0 Allows an endpoint to request authorization Allows an endpoint to request authorization

to place or accept a callto place or accept a call Allows a Gatekeeper to control access to Allows a Gatekeeper to control access to

and from devices under its controland from devices under its control Allows a Gatekeeper to communicate the Allows a Gatekeeper to communicate the

address of other endpointsaddress of other endpoints Allows two Gatekeepers to easily exchange Allows two Gatekeepers to easily exchange

addressing informationaddressing information