Collaboration Approaches for CTS05 GlobalMMCS Tutorial

CTS05 St. Louis May 17 2005

Geoffrey Fox

CTO Anabas Corporation andComputer Science, Informatics, Physics

Pervasive Technology LaboratoriesIndiana University Bloomington IN 47401

gcf@indiana.eduhttp://www.infomall.org

Material for Tutorial All talks are at

http://grids.ucs.indiana.edu/ptliupages/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

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

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

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

Typical H.323 StackH.323

IP

UDP

RTP

RTCP

TCP/UDP TCP UDPUDP TCP

Audio

Codecs

G.711

G.723.1

G.729

..

Video

Codecs

H.261

H.263

H.264

..V.150 T.120

TCP/UDP

T.38

H.225.0

Call

Signaling

H.245H.225.0

RAS

Terminal Control and ManagementData

ApplicationsMedia Control

Multimedia Applications, User Interface

http://www.packetizer.com

H.323 Endpoint (Terminal) Architecture

Video I/O equipment

LA

N

Interface

Call Control H.225.0

H.245 Control

RAS Control H.225.0

H.225.0Layer

Video CodecH.261, H.263

System Control

Audio CodecG.711, G.722, G.723, G.728, G.729

ReceivePathDelay

Audio I/O equipment

User Data ApplicationT.120, et.

System ControlUser Interface

Scope of Rec. H.323

H.323 Architecture

Gatekeeper(security, QoS, routing etc.)

MC MPMCU

H.323 Terminal 1

H.323 Terminal 2

H.323 Terminal N

....

Packet Switch Network

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

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

H.225: Call Setup Signaling

Endpoint2Endpoint1 Gatekeeper

RAS messageCall signaling message

ARQ(1)

ACF/ARJ(2)

Setup(3)Call processing(4)

ARQ(5)

ACF/ARJ(6)

Alert(7)

Connect(8)

Open a channel

H.245 Signaling H.245 is used to negotiate capabilities and to control

aspects of the conference between two or more endpoints

Endpoint EndpointTerminal Capability Set

Terminal Capability Set

M/S Determination

M/S Determination AckM/S Determination Ack

OpenLogicChannel (OLC)OLC Confirm

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 doesn’t define the conference control procedures like

multipoint parts of H.245 and T.120.

SIP Architecture

SIP Client

SIP PROXYSERVER

SIP Client

RegistrarServer

LocationServer

RedirectServer

SIP MC SIP MP

SIP MCU

rtspd

Quick-time

GatekeeperSIPUA

SIP

H.323

RTSP

sipd

sipconfsipconf

sipumsipum

sip323sip323SIP-H.323

signaling gateway

Conferencing

Programmable SIP servers

Unified messaging

Streaming media

Hardware SIP phone

Desktop SIP clients

sipgwsipgw

PSTN

MGCPSIP-MGCP gateway

SIP-PSTN gateway

Regular telephones

A Integrated SIP Service System: CINEMAFrom Columbia University

SSipconfipconf : SIP based Centralized : SIP based Centralized conferencingconferencing

sipcsipc

http://www.cs.columbia.edu/~kns10/software/sipconfhttp://www.cs.columbia.edu/~kns10/software/sipconf

SIP323SIP323

SIP/PSTNSIP/PSTN

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

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!

Access Grid I Access Grid : a large scale audio/videoconference 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

Access Grid II Supports multiple screens and dominates some

research communities

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.

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

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/)

iLBC – MOS (Audio Quality) behavior versus percentage packet loss

Skype Architecture

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

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.

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

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 don’t 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 APIsMost 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 can’t 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

What’s 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, … )

What’s 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”

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

H.323 SIPIETF

Access GridVRVS Global-MMCS

ConferenceManagement supported No supported supported supported

Overlay NetworkEnvironment

Internet / ISDNFirewall transversalunder the support of VPN

No

Need multicast support ,No firewall tunneling

Reflector InfrastructureSoftware 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 fullintegration of all tools

Floor Control

Mechanism

H.243T.120

NoUnder

developmentNo 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-CommunityCollaboration

No No No No Yes

Comparison of Global-MMCS with Competitive Systems