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H323: Architecture and Issues

Third Andean Workshop on Electronic Communications, 20-24 November 2000, Lima, PERU. H323: Architecture and Issues. Christian Benvenuti International Center for Theoretical Physics ( ICTP ), Trieste, Italy christian.benvenuti@libero.it. ICTP & Developing countries.

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H323: Architecture and Issues

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  1. Third Andean Workshop on Electronic Communications, 20-24 November 2000, Lima, PERU H323: Architecture and Issues Christian Benvenuti International Center for Theoretical Physics (ICTP), Trieste, Italy christian.benvenuti@libero.it

  2. 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. ICTP main goal To Enable the remote collaboration between scientists from developing countries and not

  4. 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. 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. 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. 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. RT Multimedia VS Streaming- Hardware needed - • RT Multimedia • Microphone • Speakers/Headphone • Whiteboard • Webcam • Scanners • ... • Streaming • Speakers

  9. RT Multimedia VS Streaming- Tipical uses - • RT Multimedia • Remote collaboration (es. paper writing) • Remote application • Streaming • Distance learning • Lectures/Seminars/Training/Univ. degree

  10. 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. 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. 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. 1st 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. 2nd 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. 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. 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. 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. STANDARDS Two main sources: • International Telecommunication Union (ITU) • H323 … (Version 4 just approved [17 Nov. 2000]) • http://www.itu.int • Internet Engineer Task Force (IETF) • RTP/RTCP, RTSP, ... • http://www.ietf.org

  19. H323 ArchitectureExample http://protocols.com/iface/voip/h323arch-b.gif

  20. H323 stack

  21. H323 Clients You can find a bigger list at: http://www.openh323.org/h323_clients.html

  22. H323 Gateway

  23. 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. H323: Gatekeeper zones

  25. H323 Gatekeeper zones (cont.) • H 225.0 - Annex G • It takes advantage by the hierarchical structure of the DNS (Domain Name System) and the way email addresses are assigned.

  26. H323 GatekeeperRouted call VS Direct call

  27. Internet Locator Service (ILS) vsGaekeeper • 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. H323 MCU

  29. H323: Main Issue ! Firewall !

  30. 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. Common “bad” solutions to the firewall problem • Microsoft suggestion: open everything! • http://support.microsoft.com/kb/articles/Q158/6/23.asp NetMeeting uses the following Internet Protocol (IP) ports: Port Purpose ------------------------------------- 389 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. 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. How to solve the firewall problem? • Intelligent firewall (Es. Cisco PIX) • $$$$$ most of the time! • Proxy • Es. PhonePatch • Web interface • NO T120 HANDLING ! ICTP  • h323 proxy (already available) • Linux Firewall with h323 handling?

  34. MBONE Tools • Vic (No h323!) • Rat/Vat • ... ... ...

  35. 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. 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. H323 opensource software • http://www.openh323.org • http://www.opengatekeeper.org • Openh323proxy (developed at the ICTP) • http://openh323proxy.sourceforge.net NO opensource MCUs are available at the moment

  38. H323: a few links • General H323 • You can find many (updated) links in my home • Security point of view (a few interesting articles) • NetMeeting Security Concerns and Deployment Issues • The Problems and Pitfalls of Getting H.323 Safely Through Firewalls • H.323 Proxy Issues Some others are in the references ...

  39. 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. 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) • RSTP (RFC 2326) • WEB • Http://www.protocols.com/voip/ • Demystifying Multimedia Conferencing Over the Internet Using the H.323 Set of Standards • IP Telephony and EIC • A Primer on the H.323 Series Standard • 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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