A. MEDDAHI (TERENA Networking Conference 2001, ANTALYA, TURKEY 14~17 May) 1 MEDDAHI Ahmed (Ecole Nouvelle d Ingénieurs en Communication) E.N.I.C Cité Scientifique,

A. MEDDAHI (TERENA Networking Conference 2001, ANTALYA, TURKEY 14~17 May)

1

MEDDAHI Ahmed (Ecole Nouvelle d Ingénieurs en Communication)

E.N.I.CCité Scientifique, rue G. Marconi

59658 Villeneuve d ’Ascq (France)

Tel: +33(0)3-20.33.55.62

Fax: +33(0)3-20.33.55.98

email: [email protected]

* this paper was supported by the European Commission through the VirTEPPE project

« Mobility issues in the context of

distance learning services »*


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CONTENT

• Introduction

• A distance learning tool based on ISDN

• A distance learning tool based on Internet

• Mobility issues

• SIP for providing distance learning services

• Conclusion


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Ecole Nouvelle d’Ingénieurs en CommunicationEcole Nouvelle d’Ingénieurs en Communication

New Communications Engineering InstituteNew Communications Engineering Institute

www.enic.frwww.enic.frwww.enic.frwww.enic.fr

Introduction


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Introduction: Channels / ActivitiesIntroduction: Channels / Activities

• Training for Engineer Degree• Training for Engineer Degree

Initial trainingInitial trainingInitial trainingInitial training 5 years5 years5 years5 years 335 for 2000335 for 2000335 for 2000335 for 2000

““Adult” trainingAdult” training““Adult” trainingAdult” training18 18

months months minimini

18 18 months months

minimini200 for 2000200 for 2000200 for 2000200 for 2000

distant trainingdistant training (for Adult only) (for Adult only)distant trainingdistant training (for Adult only) (for Adult only) 3 years3 years3 years3 years 100 for 2000100 for 2000100 for 2000100 for 2000

• On-site Training On-site Training

• Research / DevelopmentResearch / Development

• Pedagogical EngineeringPedagogical Engineering

• On-site Training On-site Training

• Research / DevelopmentResearch / Development

• Pedagogical EngineeringPedagogical Engineering

On-site training


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Tutelvisio® (a distance learning service based on ISDN)

• « Student » studio:

– Audio/video system (pan-tilt camera) controled by a specific software.

– « Question & Answer » system controled and managed by specific software and hardware.

• « Lecturer » studio:

– Audio/video system controled by a software.

– a « user friendly » GUI for managing the lecture (interactivity, audio and video sources...)

• Softwares and protocols for controling the system and for communication between remote and Local site.


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Tutelvisio® architecture

*

ISDN

Internet

H320System 256 kbs

H320System

MCU

Audio system (microphones, speakers..)

video system(pan/tilt cam.Monitor..)

Audio system

video system

« user-friendly »Soft.Soft.

« Student » studio « Lecturer » studio

T2Audio

Video

Data


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A distance learning application :

Visiocentre GUI A distance learning application :

Visiocentre GUI


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Remarks

• Benefits:– good video/audio quality (CIF/G711) and performances

(throughput up to 768 Kbs) H320 QoS.

• drawbacks:– still some interoperability problems

– difficult to deploy for individual or self training services

– deployment cost


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Tutelnet® (a distance learning tool based on Internet)

*

Internet

Web server (Html+Smil)

(Asynchronous web courses)

Streaming server(live or stored Audio/Video sources)

MCU

Client(lecturer)

Client (student)

« TutelServer® »


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Tutelnet® (components) • WEB SERVER (HTML+SMIL):

– contains Enic web courses for Asynchronous lectures (« Lecture On Demand »)

• STREAMING SERVER:

– stored audio/video lectures for Asynchronous lectures (working with the web server)

– live audio/video lectures for Synchronous lectures

• MCU :

– multipoint videoconferencing for Synchronous lectures

• « TutelSERVER » :

– specific multi-unicast software (JAVA) with enhanced services for Synchronous lectures (live « data » conferencing)


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Components (continue)

• CLIENT:

– client software (student) for accessing to « live » or « stored » lectures

– client software (lecturer) for providing and managing live lectures

» web browser

» streaming client

» H323 client» specific client (tutelbrowser®/tutelcast®)


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Tutelcast® GUI (teacher point of view)


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Tutelbrowser® GUI (student point of view)


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G.U.I (for Voice/Video/Data integration)


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Architecture (tutelnet®/tutelvisio®)

Internet

« CLIENT »(lecturer)

« CLIENT» (student)

ISDN

H320System

256 kbs

H320System

MCUH320

H323/H320Gateway

+GateKeeper


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Remarks

• Still some issues concerning interoperability (H323 systems).

• Strong issues concerning H323 through fire wall( open all UDP and TCP ports >1024).

• Heterogeneity in the access (Adsl, V90 modem, low bit rate modem, …)

• Today « our » Internet is not enough performant for supporting applications requiring interactivity

» pstn access and phone for voice interactivity

» internet only for data conferencing

» streaming server for providing a « picture » of the lecturer

• Problem of servers load need « load sharing/balancing » between multiple servers and install the servers close to the client location.

• Ip address (clients) are dynamic and change very often.

• Control access is needed.


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Mobility in the context of distance learning

• Lecturers may be in their office, lab or « outside », they want to be able to give their lectures from « anywhere »

• Students may be located at school, at home or at job office, they want to be able to access to live lectures or to a « Lecture on Demand » server

• Location of servers and content may change.

• Generaly outside university they have dynamic Ip adress from their ISP (DHCP)

• Ip address translation may occur through NAT.


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SIP Protocol

• A good mean for dynamic ip address and clients mobility issues.

• Fields in SIP headers and « SDP » message body can provide a solution to describe the type of service the client wants to access

» type of lecture and its identifier

» start time

» duration

» ...

• Provide enhanced services

» forking, call forward...

• Can be used independantly of the media stream transfert protocol.


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SIP Protocol (continue)

• RFC 2543 of the IETF MMUSIC Working Group.

• Signaling and call control protocol.

• Text oriented protocol (like Http, Smtp).

• Client/Server oriented protocol.

• Message strucure:» 1 START LINE

» 2 HEADERS

» 3 BLANK LINE

» 4 MESSAGE BODY


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Architecture for Sip (two new servers)

*

Internet

Registar serverdatabase

Sip proxy+

redirect server+

tutelServer®

client


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Different scenarios for distance learning services

Scenario 1: access to a live/asynchronous lecture*

Registar serverdatabase (registar.enic.com)

Sip proxy.enic.fr+

redirect server+

tutelServer®

database request(III) response(IV)

Multi-unicast invite(V)

(VI) data stream

« a45live »@IP1@IP2@IP3@IPn

@IP2@IP3 @IPn

Clients@IP1

REGISTER sip:registar.enic.fr SIP/2.0…subject=...content-type:application/sdp…v=0o=« lecturer ’s name paul »s=« module n° a45live »t=« 2 h »….

(I)

INVITE sip:a45live.enic.fr SIP/2.0…….

(II)


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Different scenarios for distance learning (cont.)

Scenario 2: access to a stored/Asynchronous lecture(Lecture On Demand)

Sip proxy+

redirect server+

tutelServer®

Redirect server database

INVITE sip:a45stored.enic.fr sip/2.0…content-type:application/sdp..O=P=0146532655...

302 movedcontact: <sip:server2.paris.fr>expires: 3600content-type:application/sdp..i=« Login/Pwd »...

« smart load balancing » between servers and access control


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Different scenarios for distance learning (cont.)

Scenario 3: « access » to the lecturer at a clearly defined time (« tutorat »)*

[email protected]

[email protected]

[email protected]

Registar server

Sip proxy+

redirect

INVITE sip:a45tut.enic.fr Fork the request to all possible location

INVITE sip:[email protected]



« client »student


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Conclusion

– SIP is not the only alternative H323, Megaco/h248 ...

– Etablishment of users connections goes through sip proxy (it is not mandatory), provides some means for:• acces control• Log/Statistics

– SIP is a « stand alone » protocole so it ’s possible to use it with any other media transfert protocols ( data transfert will be the first step, afterwards audio)

– Minimal configuration is required from the client side.

– Text oriented protocol facilitate understanding and implementation

– Cohabitation and interworking with other signaling protocols (H323,H248…)?

– This solution has to be fully validated.

Documents

A. MEDDAHI (TERENA Networking Conference 2001, ANTALYA, TURKEY 14~17 May) 1 MEDDAHI Ahmed (Ecole Nouvelle d Ingénieurs en Communication) E.N.I.C Cité Scientifique,