Download H.323 Revisited

網路視訊會議系統的設計與經驗
莊 志 洋
民友科技股份有限公司
Agenda
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H.323 and related protocols
Ready for right products
Design Considerations
Experiences and Suggestions
What is H.323?
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A multimedia communication protocol
suite
Includes voice, video, and data
conferencing
For use over packet-switched networks
H.323 is “ITU-T Recommendation H.323: Packet-based multimedia
communications systems”
Elements of an H.323 System
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Terminals
Multipoint Control Units (MCUs)
Gateways
Gatekeeper
Border Elements
H.323 Network Elements
H.323
Terminal
H.323
Gatekeeper
H.323
MCU
H.323
Gateway
H.323
Terminal
H.323
Terminal
PSN
GSTN
V.70
Terminal
H.324
Terminal
GQOS
LAN
Speech
Terminal
N-ISDN
H.322
Terminal
Speech
Terminal
B-ISDN
H.320
Terminal
H.321
Terminal
CSN
Terminals
MCUs
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For managing multipoint conferences
Contains
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Multipoint Controller (MC) - manages the
call signaling
Multipoint Processors (MPs) - handle
media mixing, switching, or other media
processing
Gateways
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Interface H.323 to other networks,
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Composed of
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a “Media Gateway Controller” (MGC)
a “Media Gateway” (MG)
MGC handles
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including the PSTN, H.320 systems, other H.323
networks (proxy), etc.
call signaling , non-media-related functions
MG handles the media
Gatekeeper
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Admission control
Address resolution
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e.g.,Phone number to IP address
Border Elements
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Exchange addressing information and
participate in call authorization between
administrative domains
Often co-located with a Gatekeeper,
An H.323 Stack
H.323 Application
H.245
RAS
H.225.0
Call Signaling
Packet-switched Network
RTP /
RTCP
H.323 basic protocols
Annex G
Gatekeeper Q.931/H.245 Gatekeeper
RAS
Q.931/
H.245
Q.931/
H.245
RAS
Signalling (Q.931)
Endpoint
H.245
RTP/RTCP
Endpoint
Gatekeeper Routed Signaling
Direct Routed Signaling
Source:
Lior Moscovici
H.323 related standards
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RTP/RTCP : Streaming
T.120 - Data conferencing
Audio Codecs: G.711, G.722, G.723.1,
G.728, G.729, GSM
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Video Codecs: H.261, H.263, H.264
Past to Present
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H.323 v.1 was published in 1996
was designed for LANs
Or was it?
Local Area Network
Past to Present
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But, it was used in WANs, large private
VoIP networks, and the Internet
It worked very well
Past to Present
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H.323 proved that
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RTP is able to carry real-time audio and
video over IP networks that span the globe
Indeed, H.323 was much more than a
LAN protocol
Past To Present
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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:
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Security
Performance
Supplementary Services
Scalability
Strength in Numbers
Accord Networks
Cirilium
Aethra
Cisco Systems
AG Communications
Clarent
Agilent
Comverse
Anatel
Data Connection
Aspect
Delta Information
Systems
Atlantic
Avaya
Axent
Brooktrout
Technology
Hughes Software
Systems
iBasis
IBM
Inalp Networks
Inari Inc.
Innovaphone
Motorola
Ridgeway Systems
MultiTech Systems
Siemens
Natural MicroSystems
Smith Micro
NetSpeak WebPhone
Sorenson Vision
Netergy Networks
Swyx
Network Associates
Symbol Technologies
NexTone
Telxon
TINY
Dialogic
Intel
Dialpad
ISPhone
Nuera
Communications
E-Tech Canada Ltd.
ITXC
Nx Networks
Elemedia
Ji-Tong
Communications
OKI
CUseeMe
Equivalence
Callserve
e-tel
Catapult
eZenia!
CheckPoint
FVC
China Netcom
Genuity
China Telecom
HearMe
China Unicom
Huawei
Komodo Technology
Lotus
Lucent
Macchina
Madge Networks
Microsoft
Packetizer
Pagoo
PictureTel
Polycom
Teles
Trillium
Unylogix
VCON
VegaStream
VIVE Technologies
RADCom
VTEL
VocalTec
RADVision
WowRing
Zydacron
The Market Today
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Today, the biggest market for H.323
applications is Voice over IP. Why?
Lack of right video terminals to address:
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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
Video Communication Era
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Future, expect to see video and data
communication to become more
pervasive
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Broadband connectivity is making it
possible
Video and data are logically the next
services customers expect to find in
conference rooms, at home and on their
computer screens
Why current H.323 products is
not good?
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Unstable Video Quality
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Good over dedicated lines or in demo room
Deteriorates significantly over Internet
Difficult to install
Not easy to use
Too expensive
Business model
Design Considerations
Networking environment
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Backbone band-width oversupply
Last-mile bandwidth getting better
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> 384K bps at < NT$2,000/m
xDSL, ADSL, VDSL
Cable
WLAN / WiMax
3G
IP Network Issues
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Lack of IP addresses
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Use of NAT
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Adds difficulties to address resolution
Firewall
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Dynamic IP
Virtual IP
Blocks media packets
Make plug & play less possible
Codec Issues
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Standard algorithms
Implementations:
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Computation speed
Bit rate vs picture quality
Hardware vs Software
DSP
No longer a dominating issue
Performance bottlenecks
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Not at computation unit (DSP or CPU)
Systems:
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Buffers
Internal bus
Memory speed
Graphics display
Right prices for right users
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Corporate users
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Large conference room ~NT$1.0M
Small conference room NT$50k – NT$100k
Desk top with PC ~NT$3K
Soho users < NT$50k
Home users < NT$10k
Personal users < NT$6k
Common Requirements
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接近電視的影音品質
維護容易又穩定
容易安裝，網路設定比PC簡單
不必學就會用
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慣用的撥接方式 (phone, PC, PDA, etc)
不必守在機器旁
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各式來電通知機制 (ring, e-mail, mobile, etc)
Common requirements
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固定IP、浮動IP、虛擬IP的用戶都可接通
網路擁塞 – Lack of QoS in Net
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智慧型影音流量調控
Use better end-point QoS
對話安全
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影音加密
貼近企業文化的設計
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讓傳真變彩色
PC上的資料可隨時取得
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反映手寫習慣的電子白板
輕鬆地作現場演示
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連接網路的芳鄰
遠端PC程式執行能力
遠距簡報洽商業務
異地同仁如處同地辦公
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遠距同步操作PC
貼近企業文化的設計
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多點同步會議功能
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各個角度都看得到
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內建MCU
遙控攝影機: 轉向,聚焦
多攝影機設計
保留珍貴的會議時況
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多頻道數位錄影 – 影音圖文同步錄影
Suggested HW architecture
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HW
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P4 for corporate and soho users
SOC = DSP + RSIC
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Camera
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VGA resolution at 30 fps
High-end webcam is good enough
Display
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for home and personal/mobile users
VGA monitor vs TV
Speaker and Microphone
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Headphone is uncomfortable
Conference phone is a good choice
Full duplex and echo cancellation
Suggested SW Architecture
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Embedded Linux
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Embedded Windows and GUI
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Spport P4 & RISC platforms
Complete TCP/IP stack
Small but rich
Interoperable vs compatible
Standard H.323
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Optimized implementation
Data Conference
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Work with PC / MS Windows
RDP
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Network Neighbor – Samba
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Graphical terminal
Network file system
Multi-point screen sync
T.120
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H.323 whiteboard standard
More than Data Conference
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Distance Collaboration
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Run programs
Co-design
Life demonstrations
Scratch paper – notepad
etc
Results
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嵌入式設計、多點視訊會議、影音加密、
代碼撥號、來電通知、遠端影音調控、
PC網路芳鄰、遠距簡報、電子白板與即
時圖文通訊、線上文字交談、彩色傳真、
Fax over IP Gateway、影音留言、會議
錄影
More than a H.323 system
At an affordable price
Product Varieties
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Stand-alone
Embedded in LCD monitor/HDTV
Embedded in xDSL
Built-in PDA/PPC/PMP/DSC
Must have in mobile phone
Remarks
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Internet is ready for video
communication
H.323 is a valid protocol, SIP simplifies
call setup
Multimedia communication with Voice,
video, text, graphics, 3D,
Design issues are on the system
integration, HW and SW
Embedded in various products