2. OutlineOutline
• What is H.323What is H.323
• Scope of H.323Scope of H.323
• Why is H.323 ImportantWhy is H.323 Important
• Historical Development StagesHistorical Development Stages
• Elements of H.323 SystemElements of H.323 System
• H.323 Network ArchitectureH.323 Network Architecture
• H.323 Core ProtocolsH.323 Core Protocols
• H.323: Call SignalingH.323: Call Signaling
• Prospect/Future of H.323Prospect/Future of H.323
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3. What is H.323What is H.323
H.323* is a multimedia conferencing protocol, which
includes voice, video and data conferencing for use
over packet-switched networks
Real-time multimedia communications and
conferencing for packet-based networks
* H.323 is “ITU-T Recommendation H.323: Packet-based multimedia
communications systems”
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4. Scope of H.323Scope of H.323
• Point-to-point and multipoint conferencing
support
• Inter-network interoperability
• Heterogeneous client capabilities
• Audio and video codecs
• Management and accounting support
• Security
• Supplementary services
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5. Scope of H.323Scope of H.323
5
T1524040-96
Video I/O equipment
Audio I/O equipment
User Data Applications
T.120, etc.
System Control
User Interface
Video Codec
H.261, H.263
Audio Codec
G.711, G.722,
G.723, G.728,
G.729
System Control
H.245 Control
Call Control
H.225.0
RAS Control
H.225.0
Receive
Path
Delay
H.225.0
Layer
Network
Interface
Scope of Rec. H.323
6. Why is H.323 ImportantWhy is H.323 Important
TrendTrend
Rapid growth of the Internet
Universal deployment of corporate LANs have made
packet-based networks ubiquitous
StandardizationStandardization
H.323 is a standard protocol has been widely accepted
Promotes greater awareness, availability, and
acceptability of multimedia conferencing over packet-
based networks
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7. Why is H.323 ImportantWhy is H.323 Important
Internet workingInternet working
Bridges multimedia communications between packet-
based and switched-circuit networks (SCN)
SCN conferencing standards like H.320 (ISDN), H.321
(ATM), and H.324 (PSTN) can inter-operate with H.323
clients
Integrated servicesIntegrated services
Additional services such as e-mail, voice mail, fax, call
center functionality and video conferencing in an
integrated environment
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8. Why is H.323 ImportantWhy is H.323 Important
InteroperabilityInteroperability
ConnectivityConnectivity
ETSI/ IMTC
ITU-T/ IETF
Recommendations
ProductsProductsCustomers
V
E
N
D
O
R
S
StandardsStandards
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9. Development Stages of H.323Development Stages of H.323
• H.323v1 published in 1996 & designed for LAN
– Companies tried to do use H.323 in WAN, large
private VoIP networks, and the Internet
• Guess what?
• It worked very well
• H.323 was an early adopter of IETF protocols as
RTP proved ability to carry real-time audio and
video over IP networks
– Indeed, H.323 was much more than a LAN
protocol name was changed in H.323 V2 (1998)
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10. Development Stages of H.323 (con)Development Stages of H.323 (con)
Recognizing the fact that H.323 was much more
than a LAN protocol, the name was changed in
H.323 Version 2 (1998)
Enhancements were made, including:
Security
Performance
Supplementary Services
Scalability
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11. Development Stages of H.323 (con)Development Stages of H.323 (con)
H.323 v3 introduced a few modest improvements,
mostly geared for better PSTN integration and
scalability
New annexes were introduced:
H.323 – UDP signaling
H.323 – Simple endpoint type
H.225.0 – Communication between
administrative domains
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12. Development Stages of H.323 (con)Development Stages of H.323 (con)
• H.323 v4 was approved Nov. 2000 and brings a
number of enhancements to H.323. Areas of focus
include:
– Scalability
– Services
– “Must Have” Features
– Generic Extensibility Framework
• Current version of H.323 commonly referred to as
"H.323v6” was published in 2006
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14. Scalability (con)Scalability (con)
Endpoint Capacity Reporting
By utilize endpoint capacity reporting, Gatekeepers may
select an endpoint that is best capable of handling the
call
This is extremely useful for large scale deployments of
Gateways and is also useful in call center applications
Never Lose a Call!
GK GK GK GK GK
GW
23%
GW
77%
GW
48%
GW
64%
GW
14%
GW
36%
The GK selects the GW with the most
capacity. H.323 endpoints report capacity
in absolute terms, not in percentages.
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15. ServicesServices
Annex K – Services via HTTP
Annex L – Stimulus Control
H.450.8 – Name identification
H.450.9 – Call Completion
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17. Generic Extensibility FrameworkGeneric Extensibility Framework
The Generic Extensibility Framework (GEF)
introduces a new means by which H.323 may be
further enhanced or extended with optional
features, which does not require changes to the
current ASN.1 syntax
Work has already begun
Robustness procedures (Annex R)
Local number portability
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18. Components of H.323 SystemComponents of H.323 System
Terminals
what people see/hear
Multipoint Control Units (MCUs)
provides conference capabilities
Gateways
control and ‘routing’
Gatekeeper
access to other environments
Border Elements
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20. TerminalsTerminals
An endpoint on the network which provides for
real-time, two-way communication with other
H.323 terminal, GW, or MCU
Terminal can be:
Telephones
Video phones
IVR devices
Voicemail Systems
“Soft phones” (e.g., NetMeeting®)
20
T
21. Multipoint Control Units (MCUs)Multipoint Control Units (MCUs)
Needed
only when multiparty
conferences are desired
Functions:
To manages call
signaling
Provides capability of
videoconferencing with
more than one party
Acts as a coordinator of
multiparty conferences
2121
22. Gateways (GW)Gateways (GW)
• Gateway (GW)
• used as interface H.323
between different networks
e.g. LAN & PSTN
• Functions:
• Data format translation
• Audio/video codec
translation
• Call setup, termination
from both sides of the
network
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23. Gatekeeper (GK)Gatekeeper (GK)
Gatekeeper is an optional component in H.323 system
used for:
Admission Control and
Address Resolution
Endpoints do register themselves at a Gatekeeper
All H.323 endpoints registered to a single GK build an
H.323 zone
H.323 zones are independent of physical network
topology
Each zone has only one GK (exception: Alternate
GKs)
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26. Border Elements (BE)Border Elements (BE)
Co-located with Gatekeeper, Exchange addressing
information
Participate in call authorization between
administrative domains
May aggregate address information to reduce the
volume of routing information passed through the
network
May assist in call authorization/authentication
directly between two administrative domains or
via a clearinghouse
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27. Using Elements (BE)Using Elements (BE)
27
As with hierarchical
Gatekeepers, Border
Elements may send Access
Request messages to other
Border Elements and
indicate where to send a
reply
Border Elements may also
reply directly to a request by
utilizing address
information cached from
previous exchanges with
other Border Elements
T
GK
LRQ
GK/BE
ARQ
GK/BE
AccessRequest
29. Protocols of H.323Protocols of H.323
H.323 is an umbrella of four protocols:
• Registration Admission and Status (RAS)
– define communications between endpoints and gatekeeper
– only needed when a gatekeeper exists
• H.245 - Connection Control for Capability Negotiations
• H.225/Q.931- Call Signaling (between endpoint and gatekeeper, or
between gatekeepers)
• Real-time Transport Protocol(RTP) - timely and orderly
delivery of audio and video streams
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31. Registration Admission and Status (RAS)Registration Admission and Status (RAS)
• 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
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32. Registration Admission and Status (con)Registration Admission and Status (con)
32
T GKRRQ
RCF
ARQ
(endpoint is registered)
ACF
(endpoint may place call)
DRQ
DCF
(call has terminated)
33. H.225H.225
H.225 Call Signaling
H.225 call signaling is used to establish a connection
between two H.323 endpoints
Achieved by exchanging H.225 protocol messages on
the call-signaling channel
call-signaling channel is opened between two H.323
endpoints or between an endpoint and gatekeeper
H.225 is the conference control protocol
Master/slave determination
Capability exchange
Management of media and data streams
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34. RTP/RTCPRTP/RTCP
RTP/RTCP used for audio & video over IP
networks
H.225 call signaling is used to establish a connection
between two H.323 endpoints
Achieved by exchanging H.225 protocol messages on
the call-signaling channel
call-signaling channel is opened between two H.323
endpoints or between an endpoint and gatekeeper
Real Time Transport Protocol (RTP)
end-to-end network transport function
payload type, sequence number, timestamp
RTP Control Protocol (RTCP)
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35. CODECsCODECs
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 )
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36. Voice over IPVoice over IP
36
Voice over IP (VoIP or Voice over Internet Protocol)
commonly refers to the communication protocols,
technologies, methodologies, and transmission techniques
involved in the delivery of voice communications and
multimedia sessions over Internet Protocol (IP) networks,
such as the Internet.
Other terms commonly associated with VoIP are:
IP telephony, Internet telephony, voice over broadband
(VoBB), broadband telephony, IP communications, and
broadband phone.
37. Voice over IP: ProtocolsVoice over IP: Protocols
37
Voice over IP has been implemented in various ways
using both proprietary and open protocols and
standards. Examples of the network protocols used to
implement VoIP include:
H.323
Media Gateway Control Protocol (MGCP)
Session Initiation Protocol (SIP)
Real-time Transport Protocol (RTP)
Session Description Protocol (SDP)
Inter-Asterisk eXchange (IAX)
38. Voice over IP: Protocols (con)Voice over IP: Protocols (con)
38
H.323 protocol was one of the first VoIP protocols
found widespread implementation for long-distance
traffic, as well as local area network services.
However, since the development of newer, less
complex protocols such as MGCP and SIP, H.323
deployments are increasingly limited to carrying
existing long-haul network traffic.
Session Initiation Protocol (SIP) has gained
widespread VoIP market penetration.
A notable proprietary implementation is the Skype
protocol, which is in part based on the principles of
peer-to-peer (P2P) networking.
39. Voice over IP: Business useVoice over IP: Business use
39
40. Session Initiation Protocol (SIP)Session Initiation Protocol (SIP)
40
Session Initiation Protocol (SIP) is an Internet
Engineering Task Force (IETF) standard protocol for
initiating an interactive user session that involves
multimedia elements such as video, voice, chat,
gaming, and virtual reality.
The protocol can be used for creating, modifying and
terminating two-party (unicast) or multiparty
(multicast) sessions. Sessions may consist of one or
several media streams.
Other SIP applications include video conferencing,
streaming multimedia distribution, instant
messaging, presence information, file transfer.
46. H.323 Protocol ArchitectureH.323 Protocol Architecture
ControlControl DataData Audio Video AV Control GK ControlAudio Video AV Control GK Control
signal + connection
46
Q.931Q.931
/H.22/H.22
55
H.245H.245 RTCPRTCPT.120T.120 RASRAS
H.26xH.26xG.7xxG.7xx
RTPRTP
UDPUDP
IPIP
TCPTCP
Protocol Relationships in H.323
51. Basic Call set-up with No GatekeeperBasic Call set-up with No Gatekeeper
51
t
52. Call set-up with Gatekeeper RoutingCall set-up with Gatekeeper Routing
t
52
Connect
ARQ
ACF
ACF
Alerting
Alerting
Set-upSet-up
Call Presiding
Connect
ARQ
GW GWGK
53. Call set-up with Gatekeeper RoutingCall set-up with Gatekeeper Routing
t
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54. Security Issue in H.323Security Issue in H.323
in H.323 v1
H.235 Security protocols ITU
authentication: end-point authentication
integrity: validation within a packet
privacy: encryption and decryption mechanism
non-repudiation: false denial of participation
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55. Call Enhancement in H.323Call Enhancement in H.323
H.323 v2 & v3
H.450 on top of Q.931
H.450.1 – Generic functional protocols and procedures [v1]
H.450.2 – Call Transfer [v2]
H.450.3 – Call Diversion
H.450.4 – Call Hold
H.450.5 – Call Park and Pick-up [v3]
H.450.6 – Message Waiting indication
H.450.7 – Call Waiting
H.450.8 – Name Identification[v4]
H.450.9 – Call Completion
H.450.10 – Call Offer
H.450.11 – Call Intrusion and so on…
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56. H.323: Market TodayH.323: Market Today
Today the biggest market for H.323 applications is
Voice over IP.
Why?
Low bit-rate Internet connections make video and data
intensive applications less appealing
It’s a young industry– and with all such industries, it
takes time to mature good products
Companies can provide VoIP services today at a low
cost and provide new competition to the incumbent
carriers
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57. H.323: The Changing MarketH.323: The Changing Market
Tomorrow, expect to see video and data
conferencing to become more pervasive
Broadband connectivity is making it possible
Video and data are logically the next services
customers expect to find in conference rooms and on
their computer screens
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58. H.323: Beyond Voice over IPH.323: Beyond Voice over IP
Voice over IP opens the door to the next generation
of communication products
It will take some time to migrate the world from
PSTN to IP networks
H.323 provides excellent interworking between IP
networks and the PSTN
H.323 provides a strong foundation for new multimedia
products and services
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59. H.323: IP TelephonyH.323: IP Telephony
• IP Telephony with H.323 truly means Multimedia
over IP
• IP Telephony is not Just Research Topic Anymore
– is now real… there are many deployed products and
services that offer IP Telephony services
– new kinds of services are now available to customers
using IP Telephony that were never possible before
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60. H.323: Makes All PossibleH.323: Makes All Possible
H.323 makes it possible to create and deploy new
services quickly and to take advantage of
multimedia capabilities
These services can embrace audio, video, and
data conferencing
- Application Sharing - Electronic Whiteboard - File Transfer
- Instant Messaging - Click to Dial - Internet Call Waiting
- Web Call Parking - Call No-Waiting - Ad-Hoc Conferencing
- Voicemail Anywhere - Unified Messaging - Service Portability
- Services! - Services! - Services!
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61. H.323: for Service ProviderH.323: for Service Provider
H.323 is a proven technology that is utilized in
large networks, such as Genuity, iBasis, ITXC,
China Unicom, and others
Excellent integration with the PSTN
Gateways and residential devices are in use today
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62. H.323: in the EnterpriseH.323: in the Enterprise
Multimedia conferencing devices show the real
potential of H.323 and multimedia communication
With H.323 in the service provider network, H.323 is
a logical choice for the enterprise
The enterprise customer wants voice, video, and data
conferencing capabilities
62
63. Importance of H.323Importance of H.323
Interoperability - H.323 establishes methods for receiving
clients to communicate capabilities to the sender
Network independence - H.323 is not tied to any
hardware or operating system
H.323 sets multimedia standards for the existing
infrastructure (i.e. IP-based networks)
H.323 conference can include endpoints with different
capabilities
H.323 provides multiple audio and video CODECs that
format data according to the requirements of various
networks, using different bit rates, delays, and quality
options.
63
64. Importance of H.323 (con)Importance of H.323 (con)
Although H.323 can support conferences of three or more
endpoints without requiring a specialized multipoint
control unit, MCU's provide a more powerful and flexible
architecture for hosting multipoint conferences
Although H.323 can support conferences of three or more
endpoints without requiring a specialized multipoint
control unit, MCU's provide a more powerful and flexible
architecture for hosting multipoint conferences
H.323 supports multicast transport in multipoint
conferences
H.323 has the support of many computing and
communications companies and organizations
64
66. Recommendation AnnexesRecommendation Annexes
H.323
Annex C – H.323 over ATM
Annex D – H.323 FAX
Annex E – UDP operation
Annex F – Simple Endpoints
Annex J – Security for Simple endpoints
Annex K – HTTP based call control
Annex M – Tunneling of QSIG in H.323
H.225.0
Annex G – Inter-Domain Communications
Annex H – ASN.1 Syntax
66
67. ConclusionConclusion
H.323 is a protocol that leverages the strength
of the packet-switched protocols from the
IETF
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
67
68. AcronymsAcronyms
• ARQ –Admission Request message
• BE – Border Element
• GEF – Generic Extensibility Framework
• GK – Gatekeeper
• GW – Gateway
• IETF – Internet Engineering Task Force
• IMTC – International Multimedia Telecommunications
Consortium
• IP – Internet Protocol
• IVR – Interactive Voice Response
• LAN – Local Area Network
• LRQ – H.225.0 Location Request message
• MCU – Multipoint Control UnitMC – Multipoint Controller
• MG – Media Gateway
• MGC – Media Gateway Controller
• MP – Multipoint Processor
• PSTN – Public Switched Telephone Network
68
69. AcronymsAcronyms
• RFC – Request for Comments
• RTP – Real-Time Transport Protocol
• RTCP – Real-time Transport Control Protocol
• TCS – H.245 Terminal Capability Set message
• UDP – User Datagram Protocol
• URL – Uniform Resource Locator
• VoIP – Voice over IP
• MC – Multipoint Controller
• MG – Media Gateway
• MGC – Media Gateway Controller
• MP – Multipoint Processor
• PSTN – Public Switched Telephone Network
• RFC – Request for Comments
• RTP – Real-Time Transport Protocol
• RTCP – Real-time Transport Control Protocol
• TCS – H.245 Terminal Capability Set message
• UDP – User Datagram Protocol
• URL – Uniform Resource Locator
• VoIP – Voice over IP
69
ITXC - Internet Telephony Exchange Carrier (US based wholesale provider of VoIP China has adopted H.323 as their national standard for IP telephony communications
