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H323: Architecture and Issues Christian Benvenuti International Center for Theoretical Physics (ICTP), Trieste, ItalyICTP

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Presentation on theme: "H323: Architecture and Issues Christian Benvenuti International Center for Theoretical Physics (ICTP), Trieste, ItalyICTP"— Presentation transcript:

1 H323: Architecture and Issues Christian Benvenuti International Center for Theoretical Physics (ICTP), Trieste, ItalyICTP Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU

2 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU ICTP & Developing countries Developing countries often means – No 24x7x365 internet connection – Low bandwidth links Bad phone line quality (PPP problems...) – Satellite link ? Scientific Computer Section mailstones – www4mail (Enrique is talking about this) (...) – Scientific talk – Mbone tools – Streaming – H323 Architecture

3 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU ICTP main goal To Enable the remote collaboration between scientists from developing countries and not

4 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU RealTime multimedia VS Streaming They differ from many point of view: Number of “entities” involved Degree of interaction between the remote ends Protocols involved Hardware needed Network constraints Buffering usage Realtime multimedia ?=? Remote collaboration Streaming ?=? Distance learning

5 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU Real time multimedia Most of the time it is 1 to 1 – When it is “n” to “m” it can be very expensive High level of interaction Main constraints: delay and jitter No buffering More hardware needed

6 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU Streaming Usually 1 to “n” (with “n” >>> 1) Very small interaction Buffering on the client side No specific HW is needed (on the client side) Asymmetric (client-server)

7 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU RT Multimedia VS Streaming - Software needed - RT Multimedia – Cheaper (most of the time free) for basic configurations – Netmeeting/DCShare/Sunforum/... /Mbone tools Streaming – The server (Real Server/Windows media server) can be very expensive while the client is usually free (Real Player/Windows media player) Sure stream technology

8 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU RT Multimedia VS Streaming - Hardware needed - RT Multimedia Microphone Speakers/Headphone Whiteboard Webcam Scanners... Streaming Speakers

9 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU RT Multimedia VS Streaming - T ipical uses - RT Multimedia Remote collaboration (es. paper writing) Remote application Streaming Distance learning –Lectures/Seminars/Training/Univ. degree

10 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU RT Multimedia VS Streaming - Protocols - RT Multimedia Real Time Protocol /Real Time Control Protocol (over UDP/IP) Poor UDP/IP Streaming Real Time Streaming Protocol (RTSP) –This still uses RTP for live content! Microsoft ASX –No Clients for Linux (Wine and/or VMWare?)

11 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU RT Multimedia VS Streaming - Bandwidth usage - RT Multimedia – It depends very much on the media used Streaming – Usually the server is able to stream the same content using different bandwidths depending on the client’s link speed

12 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU Let’s focus on RT Multimedia ICTP has recently started working on a streaming project for many reasons... ICTP main focus is still RT Multimedia

13 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU 1 st Rule Remote collaboration is not (and it does not claim to be) like face to face collaboration and it will probably never be like that – May be one day when virtual reality will not be only a game anymore … (is it what we want?)

14 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU 2 nd Rule The computer does not have to be seen as a sobstitute to human interaction – It is only an instrument! Distance/Computer based training will never sobstitute teachers completely! (I HOPE) – This is especially important for young people

15 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU Remote collaboration: what hardware do we need? Basic configuration – Standard PC – Sound card + Speakers – Microphone Optional devices – Webcam/camera – Scanner – Tablet (es. Wacom, Mimio, etc) – NETWORK CONNECTION

16 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU What media can we use to collaborate? Voice Video (optional?) Chat Whiteboard File sharing (easier that mail attach. and ftp) Application sharing – Web Sharing...

17 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU ICTP main prefixed goals Easiness of use Security under control Possibly no change to the everyday hw/sw instruments used by the users Cheap hw/sw (opensource/Linux)... in other words... as plug an play as possible!

18 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU STANDARDS Two main sources: International Telecommunication Union (ITU) – H323 … (Version 4 just approved [17 Nov. 2000]) Internet Engineer Task Force (IETF) – RTP/RTCP, RTSP,...

19 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 Architecture Example

20 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 stack

21 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 Clients O.S.ClientPrice WindowsNetMeeting +/- free Unix (Linux)DC-Share nv SunSunforum+/- free … You can find a bigger list at:

22 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 Gateway

23 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 Gatekeeper Main tasks Zone control Admission control Call authorization Bandwidth control Address translation … … … Main issue: Being not hierarchical it does not scale! –ANNEX H

24 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323: Gatekeeper zones

25 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 Gatekeeper zones (cont.) H Annex G – It takes advantage by the hierarchical structure of the DNS (Domain Name System) and the way addresses are assigned.

26 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 Gatekeeper Routed call VS Direct call

27 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU Internet Locator Service (ILS) vs Gaekeeper ILS is a Microsoft extension to the LDAP protocol It is used to make it easier for Netmeeting users to find each other – It is not hierarchical – It is not included in the h323 arch. – It can NOT interoperate with a gatekeeper – It is disappearing

28 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 MCU

29 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323: Main Issue ! Firewall !

30 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 and firewalls do not coexist very well yet! The h323 architecture has not been designed taking into account the poor network administrators... The use of DYNAMIC PORTS makes it impossible for a standard packet filtering firewall to cleanly allow that protocol!

31 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU Common “bad” solutions to the firewall problem Microsoft suggestion: open everything! NetMeeting uses the following Internet Protocol (IP) ports: Port Purpose Internet Locator Server [Transmission Control Protocol (TCP)] 522 User Location Server (TCP) 1503 T.120 (TCP) 1720 H.323 call setup (TCP) 1731 Audio call control (TCP) Dynamic H.323 call control (TCP) Dynamic H.323 streaming [Realtime Transport Protocol (RTP) over User Datagram Protocol (UDP)]

32 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU Common “bad” solutions to the firewall problem (cont.) On the firewall you can open: – Only a given set of internal IPs/Networks or – Only traffic from a given set of external IPs/Networks or – Only a given range of ports

33 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU How to solve the firewall problem? Intelligent firewall (Es. Cisco PIX) – $$$$$ most of the time! Proxy – Es. PhonePatchPhonePatch Web interface NO T120 HANDLING ! ICTP  – h323 proxy (already available) h323 proxy – Linux Firewall with h323 handling?

34 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU MBONE Tools Vic (No h323!) Rat/Vat

35 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 vs MBONE (For the sake of completeness) Scientific VS Commercial Communities Architecture VS not Architecture oriented Single suite VS Multiple indipendent tools but COMMON RTP USAGE Can they interoperate ?

36 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 vs SIP H323 is a binary protocol (ASN.1) while SIP is text based like HTTP (which means easier to deal with) SIP is newer SIP is much simpler to implement SIP handles better the firewall problem SIP is more focused on IP telephony … but … H323 is already the de facto standard!

37 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323 opensource software Openh323proxy (developed at the ICTP)ICTP – NO opensource MCUs are available at the moment

38 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU H323: a few links General H323 – You can find many (updated) links in my home You can find many (updated) links in my home Security point of view (a few interesting articles) – NetMeeting Security Concerns and Deployment Issues NetMeeting Security Concerns and Deployment Issues – The Problems and Pitfalls of Getting H.323 Safely Through Firewalls The Problems and Pitfalls of Getting H.323 Safely Through Firewalls – H.323 Proxy Issues H.323 Proxy Issues Some others are in the references...

39 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU To summarize... Realtime multimedia VS Streaming – Standard Organizations (ITU, IETF) H323 is still a too fresh architecture – Security issues not completely solved The ICTP is working on a cheap/PnP solution

40 Third Andean Workshop on Electronic Communications, November 2000, Lima, PERU References (where I also took most of the images) International Telecommunication Union (ITU) – H.323 (It is NOT on line) Internet Engineer Task Force (IETF) – RTP/RTCP (RFC 1889) RTP/RTCP (RFC 1889) – RSTP (RFC 2326) RSTP (RFC 2326) WEB – – Demystifying Multimedia Conferencing Over the Internet Using the H.323 Set of Standards Demystifying Multimedia Conferencing Over the Internet Using the H.323 Set of Standards – IP Telephony and EIC IP Telephony and EIC – A Primer on the H.323 Series Standard A Primer on the H.323 Series Standard – Multimedia Standards - H.323 for Audio Visual Conferencing Multimedia Standards - H.323 for Audio Visual Conferencing Some others are in my homepage (http://shannon.csr.unibo.it/benve/h323.html)


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