Collaboration Approaches for CTS05 GlobalMMCS Tutorial

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Collaboration Approaches for CTS05 GlobalMMCS
Tutorial

• CTS05 St. Louis May 17 2005
• Geoffrey Fox
• CTO Anabas Corporation and
• Computer Science, Informatics, Physics
• Pervasive Technology Laboratories
• Indiana University Bloomington IN 47401
• gcf_at_indiana.edu
• http//www.infomall.org

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Material for Tutorial

• All talks are at http//grids.ucs.indiana.edu/ptli
  upages/presentations/cts05/
• Both tutorial and conference presentations (Ahmet
  Uyar, Sangyoon Oh)
• Open source Software at
• http//www.globalmmcs.org and
• http//www.naradabrokering.org (Software Overlay
  Network)
• http//www.collab-ogce.org/nmi/index.jsp (Grid
  Portals)
• More information about our work
  http//www.infomall.org

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Tutorial Overview 5 Sections

• Overview of existing audio/video systems we are
  trying to address general real-time collaboration
  but we A/V systems have hard technical challenges
• Apply to WebEx, Placeware style shared
  applications as well
• Grids and Web Services current preferred
  approach to distributed systems but main focus
  asynchronous sharing we will apply to
  synchronous case
• Grids are Internet-Scale Distributed Services
• Message-oriented Middleware or Software Overlay
  Networks natural approach to both Grids and
  Collaboration spanning P2P and Server-based
  scalable systems NaradaBrokering
• XGSP provides Web Service (Grid) interfaces for
  Collaboration
• Finally GlobalMMCS is the collaboration
  environment

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H.323 Introduction

• Major audio-video standard but broader
• Binary format for both data and control
• Supported by many commercial vendors and used
  throughout the world in commercial and
  educational markets
• Supports small-scale multipoint conferences
• Has conference management functionality and the
  call signaling functionality
• H.225 call set-up
• H.245 call control
• H.243 Audio/Video multipoint control
• T.120 Data Collaboration

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H.323 Protocols

• H.323 is a framework document that describes
  how the various pieces fit together
• H.225.0 defines the call signaling and
  communication between endpoints (Call Signaling)
  and the Gatekeeper (RAS)
• Annex G/H.225.0 defines communication between
  Border Elements
• H.245 is the conference control protocol

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Typical H.323 Stack
http//www.packetizer.com
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H.323 Endpoint (Terminal) Architecture
Video Codec H.261, H.263
Video I/O equipment
Receive Path Delay
Audio Codec G.711, G.722, G.723, G.728, G.729
Audio I/O equipment
LAN Interface
H.225.0 Layer
User Data Application T.120, et.
System Control
H.245 Control
System Control User Interface
Call Control H.225.0
RAS Control H.225.0
Scope of Rec. H.323
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H.323 Architecture
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H.323 MCU

• 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

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H.323 Gatekeeper

• Admission Control
• Bandwidth Control
• Address Resolution
• DNS style service for VoIP and
  Videoconferencing
• Directory Service
• Call routing
• route the call to MCUs

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H.225 Call Setup Signaling
Endpoint2
Endpoint1
Gatekeeper
ARQ(1)
ACF/ARJ(2)
Setup(3)
Call processing(4)
ARQ(5)
ACF/ARJ(6)
Alert(7)
Connect(8)
RAS message Call signaling message
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H.245 Signaling

• H.245 is used to negotiate capabilities and to
  control aspects of the conference between two or
  more endpoints

Terminal Capability Set
Endpoint
Endpoint
M/S Determination
Terminal Capability Set
M/S Determination Ack
M/S Determination Ack
OpenLogicChannel (OLC)
Open a channel
OLC Confirm
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SIP

• Initially SIP was designed to solve problems for
  IP telephony.
• SIP basic functions
• user location resolution,
• capability negotiation
• call management.
• equivalent to the service H.225 and point to
  point part of H.245
• The major difference from H.323
• SIP was designed in a text format and took
  request-response protocol style like HTTP
• SIP doesnt define the conference control
  procedures like multipoint parts of H.245 and
  T.120.

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SIP Architecture
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A Integrated SIP Service System CINEMA From
Columbia University
Desktop SIP clients
H.323
sip323
Gatekeeper
SIP-H.323 signaling gateway
sipd
SIP
Programmable SIP servers
Conferencing
Hardware SIP phone
sipum
Unified messaging
sipgw
RTSP
rtspd
SIP-MGCP gateway
MGCP
Streaming media
SIP-PSTN gateway
PSTN
Regular telephones
CINEMA clouds
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Sipconf SIP based Centralized conferencing

• SIP based conferencing server
• SIP/SDP and RTP/RTCP
• Audio mixing
• Play-out delay algorithm
• Web based conference setup
• G.711 A and Mu law, G.721, DVI ADPCM
• Multiple simultaneous conferences

http//www.cs.columbia.edu/kns10/software/sipconf
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Summary of H.323/SIP Conferencing Systems

• Most products are Centralized conferencing system
• MCU integrates the service of media
  processing service and session management
• Call-based
• A conference call represents control
  connections between clients and MCUs.
• Most vendors offer hardware solutions
• Thought as services and controllers but
  specialized protocols and implementations NOT
  Service-Oriented Architectures!

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Access Grid I

• Access Grid a large scale audio/videoconferen
  ce based on a multicast network
• provides the group-to-group collaborations among
  150 nodes connected to Internet 2 world wide.
• Use improved MBONE audiovisual tools VIC and RAT
• Depends upon high-speed network ( each node needs
  20Mbps )
• Peer to peer architecture for distribution with
  centralized non standard session control (venue
  server)
• Did not develop many new capabilities but made
  existing public domain software better packaged
  and easier to use

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Access Grid II

• Supports multiple screens and dominates some
  research communities

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VRVS Virtual Rooms VideoConferencing System

• VRVS is a project from particle physics group at
  Caltech that extends the service of Access Grid.
• VRVS builds its collaboration service on top of
  pure software reflector infrastructure which is a
  kind of software multicast. (similar to
  NaradaBrokering )
• It is capable of supporting MBONE tools, H.323
  terminal as well as QuickTime player.
• It also supports shared web browsing and shared
  desktop (VNC).
• VRVS is not an open project having few documents
  for their architecture and conference control
  framework.

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Skype I

• Skype p2p VoIP solution and has become a huge
  success.
• A Peer-to-peer overlay network for VoIP and
  Instant messages developed by founders of KaZaA.
• using p2p overlay (Kazaa) rather than expensive,
  centralized infrastructure
• Free on-net VoIP service and a fee-based off-net
  SkypeOut service that allows calling to PSTN and
  cellular phones
• provided supplemental features like instant
  messaging service.
• Millions of download and on-line users in the
  world

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Skype II

• Based on Kazaa Overlay network
• Unstructured p2p file sharing overlay
• Overlay p2p network consisting of ordinary and
  Super Nodes (SN).
• Ordinary node connects to network through a Super
  Node.
• Centralized authentication server
• Excellent Audio quality based on Internet Low Bit
  rate Codec ILBC (http//rfc3951.x42.com/)

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iLBC MOS (Audio Quality) behavior versus
percentage packet loss
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Skype Architecture
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Skype III

• Each client maintains a list of super nodes in
  the Host Cache.
• Buddy list is local to a machine.
• Skype client continuously discovers and builds
  the list of Skype nodes.
• Use a hybrid DHT and flooding mechanism to search
• A Super Node acts a proxy for clients and caches
  the result

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Skype IV

• Skype client listens on configured TCP and UDP
  ports.
• Uses a variant of STUN to identify the type of
  NAT and firewall.
• Usage of TCP port 80 enables client to reach
  super node even through firewalls.
• Call signaling is done over TCP, messages are
  preferably transported over UDP.
• In the presence of NAT or firewalls, calls
  between caller and callee are routed by an
  intermediate node
• All Skype messages are encrypted.

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Why is Skype so successful?

• Better voice quality
• excellent audio codec, fancy echo cancellation
  algorithm
• Global IP Sound ( iLBC audio codec )
• Ability to work behind firewalls and NAT
• Ease of use ( quite simple UI ) based on IM
  metaphor
• P2P style without centralized MCU
• any peer that has enough resource can be
  selected to host the mixing service
• limited the number of participants in a
  conference ( at most 4 which is common for
  private social meetings )
• use p2p overlay to discover resources and
  route packets

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But they are simply not good enough!

• Although all of these systems have
  advantages, they are not sufficient for building
  more advanced and integrated collaboration
  systems
• SIP very limited supported for conference
  control
• H.323
• AV collaboration and T.120 are not well
  integrated.
• the AV communication services and T.120 overlay
  networks dont have very good scalability.
• H.323 and T.120 are designed in a relative
  complicated OSI model. It is not easy to
  understand and develop in their APIs
• Most H.323 and SIP conferencing products are
  based on centralized MCU
• Access Grid heavily depends on multicast
  service and limited number of uni-cast bridge
  servers in the Internet 2
• No way to be deployed in current Internet
• VRVS No clear way to generalize
• Skype Most promising
• use their own propriety protocols and cant
  interoperate with other legacy VoIP clients such
  as H.323 and SIP
• only support small-scale audio conferencing ( at
  most 4-party ) and have no video service

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Whats the ideal videoconferencing system I

• A unified, scalable, robust overlay network is
  needed to support AV and data group communication
  over heterogeneous networking environments
• go through firewall and NAT
• provide group communication service in whatever
  unicast and multicast networks
• offer reliable data delivery in whatever loss
  network
• to be configured as P2P or distributed
  server-based overlay to provide differential
  services for VIP and regular users
• Publish-Subscribe collaboration mechanism natural
  for centralized and P2P modes
• A service-oriented architecture for hosting media
  processing service and session control service
• More scalable than centralized MCU
• Support various style of conferencing ( massive
  scale of broadcasting as well as medium size of
  private social meetings )
• Service providers can be highly distributed and
  p2p
• Skype p2p audio mixing
• Scalable service discovery based on p2p search
• Customized media filters for different clients (
  PC, PDA, )

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Whats the ideal videoconferencing system II

• A core conference control mechanism is required
  for establishing and managing the multi-point
  conference
• Complete conference control service like T.124
  (Generic Conference Control) in T.120 framework
• more flexible facilities to describe application
  sessions and entities ( role-based, XML )
• Integrate different AV sessions ( H.323 , SIP,
  Access Grid, RealStreaming )
• Introduce a common AV signaling protocol to
  interoperate different AV collaboration endpoints
  
• Simply regard these bridging gateways as
  add-on services

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Global-MMCS is one approach to the ideal
conferencing solution

• NaradaBrokering as software overlay
• Group communication
• Service discovery
• Skype and VRVS also are based on similar idea
• XGSP is Web Service compatible conferencing
  framework
• Service management
• Conference control
• Common AV signaling protocol
• Publish-Subscribe as collaboration mechanism
• Easy to support new applications
• Services with SOA as components
• Codec conversion or video mixing are separate
  services
• Grids are high performance large scale sevices

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H.323 SIP IETF Access Grid VRVS Global-MMCS
Conference Management supported No supported supported supported
Overlay Network Environment Internet / ISDN Firewall transversal under the support of VPN No Need multicast support , No firewall tunneling Reflector Infrastructure Software Multicast Publish/Subscribe Firewall NAT transversal (VPN optional)
Data Collaboration Limited T.120 whiteboard, File FTP No Limited to ( PowerPoint, Chat ) Limited to ( Shared browsing and VNC ) allows full integration of all tools
Floor Control Mechanism H.243 T.120 No Under development No No Chairman based Flexible role setting
Scalability Not good Not good Good Good Good
Support heterogeneous clients No No No H.323, MBONE H.323, SIP, MBONE, RealPlayer, PDA, Cell Phone
Community- To-Community Collaboration No No No No Yes
Comparison of Global-MMCS with Competitive Systems