Transcript Real Time Communications

Real Time
Communications
Presented by Sebastian Neaga
Presentation Overview
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Introduction
Applications and Technologies
Instant Messaging and Chat
 Video Conferencing
 VoIP and IP Telephony
 Grid Computing
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In-depth look at VoIP
Today
Applications:
Instant Messaging and Chat
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Communication Prerequisites
Architecture
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Client/Server
Mixed Client/Server and Client-to-Client
Pear-to-pear
Standards
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Internet Relay Chat (IRC)
T.120 (Data protocol for multimedia)
Applications:
Video Conferencing
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What is Video Conferencing
Problems with NAT and
Firewall?
International Telecommunication
Union
Applications:
Video Conferencing (cont.)
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H.310
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H.320
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H.321
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H.322
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H.323
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H.324
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T.120
Broadband audiovisual communication
systems and terminals
Narrow-band visual telephone systems
and terminal equipment
Adaptation of H.320 visual telephone
terminals to B-ISDN environments
Visual telephone systems and terminal
equipment for local area networks
which provide a guaranteed quality of
service
Packet-based multimedia
communications systems
Terminal for low bit-rate multimedia
communication
Data protocols for multimedia
conferencing
Applications:
VoIP and IP Telephony
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VoIP and IP Telephony are
forms of communications over
Internet Protocols (IP) rather
than over the Public Switched
Telephone Network (PSTN)
VoIP focuses on LAN’s where
the IP Telephony focuses on
replacing the PSTN networks
Applications:
VoIP and IP Telephony (cont.)
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Basic Concepts
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Conversion analog signals to digital format using
CODECs from the G.7xx family
Translation of digital signals to IP packets
Transmission of IP packets over the Internet
Communication Concepts
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Easy way to setup and end a call
Making calls should be as simple as dialing
Directory services
Applications:
VoIP and IP Telephony (cont.)
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VoIP implementation
Applications:
VoIP and IP Telephony (cont.)
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IP Telephony Implementation
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Media Gateway (MG)
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Media Gateway Controller or call agent (MGC)
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provides translations between circuit switched
networks and packet switched networks in terms
of media flows
sends notification to the MGC about endpoint
events
execute commands from the MGCs
provides call signaling, control and processing
intelligence to the gateway
sends and receives commands to/from the
gateway
Signaling Gateway (SG)
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provides signalling translations between circuit
switched networks and packet switched networks.
Applications: Grid Computing
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Distributed Computing
Point of Sale terminals
 Virtual Organization (VO)
 Third Party Data Manipulation
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VoIP
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Aproaches
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Complex Protocol/Simple Architecture
Complex Architecture/Simple Protocol
Standards
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H.323 is a standard developed by the
International Telecommunications Union
which defines a group of protocols over
the Packet Based Networks (PBN)
which may not necessarily provide
guarantee quality of service
VoIP
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H.323
H.225
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H.235
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H.245
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H.450
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H.246
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H.332
H.26x
G.7xx
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Specification of the architecture
Call control, call setup, and packetization
and synchronization of media stream
Security protocol for authentication,
integrity, privacy, etc.
Capability exchange communication and
mode switching
Supplementary services including call
holding, transfer, forwarding, etc.
Interoperability with circuit-switched
services
For large size conferencing
Video codecs (H.261, H.263)
Audio codecs (G.711, G.723, G.729, etc.)
VoIP
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Standards
Session Initiation Protocol (SIP)
developed by The Internet
Engineering Task Force (IETF) is
an application layer protocol that
defines the initiation, modification
and termination of multimedia
communications
VoIP
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UAC (User Agent Client)- the end-user system sending SIP requests
(initiating or terminating a call);
UAS (User Agent Server)- the end-user system handling call requests
(receiving or terminating a call);
UA (User Agent) - the combination of UAC and UAS;
Proxy Server (PS)) - a network server handling UA requests and
responses in proxy mode (acting as both a server and a client to make
requests on behalf of other clients);
Redirect Server (RS)- a network server handling user location services in
redirect mode (unlike the PS that initiates its own SIP request);
Registar Server - a network server able to accept UA registrations;
Location Server - a network server able to provide user location services
(in order to obtain information about a called party's possible location).
VoIP
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SIP Protocol
INVITE
 BYE
 CANCEL
 OPTIONS
 ACK
 REGISTER
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VoIP
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H.323 or SIP?
Questions
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G.711 PCM A-Law/u-Law
G.726 ADPCM
G.727 E-ADPCM
G.729 CS-ACELP
G.728 LD-CELP
G.723.1 CELP
64 Kbps (DS0)
16, 24, 32, 40 Kbps
16, 24, 32, 40 Kbps
8 Kbps
16 Kbps
6.3/5.3 Kbps Variable
Sources
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PCWorld
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GNRT
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http://gnrt.terena.nl/content.php?section
_id=5
Wikipedia
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http://pcworld.com/article/id,119940page,1/article.html
http://en.wikipedia.org/wiki/Voice_over_I
P
Progia
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http://www.contentbyexperts.com/