3. H.323 is not actually a protocol that
you'll see on the network
it's what we call an Umbrella
Protocol & it is from the
International Telecommunications
Union Telecoms sector, so it actually
includes a bunch of sub protocol’s.
What is H.323?
4. H323 intro :
o H.323 is a multimedia conferencing protocol, which includes voice,
video & data conferencing for use over Packet-switched networks.
o So, H.323 is a standard specified for Packet-based Multimedia
Communications Systems by ITU-T.
o H.323 suite is an ´Umbrella´ standard, references to other standards
and ITU recommendations.
5. Local Area Network
The 1st version of H.323 protocol was published in 1996 &
was “designed for Local Area Networks”
6. The first thing companies tried to do was use H.323 in Wide
Area Networks, large private VoIP networks & the Internet
◦ Output result : it worked very well
7. H.323 version 4 was approved November 17, 2000 &
brings a number of enhancements to H.323.
Areas of focus include:
◦ Scalability
◦ Services
◦ “Must Have” Features
◦ Generic Extensibility Framework
8. H.323 Standards
Network
Non-guaranteed Bandwidth packet-switched
networks (e.g. IP)
Video H.261, H.263
Audio G.711, G.722, G.728, G.723, G.729
Call signaling & media
packetisation
H.225
Call Control H.245
Multipoint H.323
Data T.120
9. Elements of an H.323 System
1. Terminals
2. Multipoint Control Units (MCUs)
3. Gateways
4. Gatekeeper
5. Border Elements
Referred to as
“endpoints”
11. Multipoint Control Units: (MCUs)
Responsible for managing multipoint conferences (two or more
endpoints engaged in a conference)
The MCU contains a Multipoint Controller (MC) that manages the
call signaling & may optionally have Multipoint Processors (MPs) to
handle media mixing, switching or other media processing
MCU
MC MP
12. Gateways
The Gateway is composed of a “Media Gateway Controller” (MGC)
& a “Media Gateway” (MG), which may co-exist or exist separately
o The MGC handles call signaling & non-media-related functions
o The MG handles the media
GW
13. Gatekeeper
The Gatekeeper is an optional component in the H.323 system
which is used for admission control & address resolution
The gatekeeper may allow calls to be placed directly between
endpoints or it may route the call signaling through itself.
GK
14. Border Elements
which are often co-located with a Gatekeeper, exchange addressing
information & participate in call authorization between
administrative domains
It may aggregate address information to reduce the volume of
routing information passed through the network
BE
15. Zone
GK
GW
MCU
T
There is no imposed limit on the number or types of
devices in a zone
A single Gatekeeper & all of the devices connected to it
The physical location of the Gatekeeper with respect to its endpoints
is immaterial
16. Administrative Domain
There is no specified limit on the number of Zones
within an Administrative Domain
A collection of Zones that are under a single administrative control
(e.g. a service provider or enterprise network)
17. Topology with RAS
GK GK
T T MCU GW
GK
GK GK
GWGWGWGW
GK
Hierarchical Gatekeeper topology is
widely used, but explicitly discussed
in H.323
22. Registration, Admission & Status - RAS (cont)
T GK
RRQ
RCF
ARQ
(endpoint is registered)
ACF
(endpoint may place call)
DRQ
DCF
(call has terminated)
28. Comments on H.323
H.323 is scalable
H.323 allows the use of multiple codecs
H.323 is a very complex system with all of kinds of features for multimedia
communications
H.323 is a proven technology used in large networks. It has excellent integration with
PSTN.
Multimedia conferencing shows the real potential for H.323 used in multimedia
communication
29. H.323 is organized around four major facilities: (a) terminals, (b)
Gateways, (c) Gatekeeper & (d) MCUs
A principal technology for the transmission of real-time audio, video, &
data communication over packet-based networks
Multipoint & point-to-point sessions.
A rich & complex specification
Scalable, reliable, flexible system,
Supplementary services & new features are powerful
Conclusions
