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Challenges and Solutions for H.323 Multimedia Communications Through Firewalls and NAT

This document discusses the complexities of H.323 packet-based multimedia communication systems, particularly the challenges posed by firewalls and NAT (Network Address Translation). It highlights two key problems: the blocking of Q.931 SETUP messages and the masking of internal endpoint addresses. The report presents three approved standards for overcoming these challenges: H.460.17, H.460.18, and H.460.19. These solutions include tunneling RAS messages, creating pinholes for incoming RTP/RTCP packets, and other modifications to enhance connectivity through restrictive environments.

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Challenges and Solutions for H.323 Multimedia Communications Through Firewalls and NAT

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  1. Multimedia Communications and Firewall/NAT CS525 By Saroj Patil

  2. Objective • H.323 - Packet-Based Multimedia Communications Systems • Problems penetrating firewall and establishing connection with endpoint behind firewall • H.460.17/18/19 CS525 - Saroj Patil

  3. H.323 Family of protocols – CS525 - Saroj Patil

  4. H.323 Call Setup CS525 - Saroj Patil

  5. Problems Posed by Firewall / NAT Problem 1 : Q.931 SETUP message blocked by Firewall CS525 - Saroj Patil

  6. Problems Posed by Firewall / NAT Problem 2 : NAT hides internal endpoint address by replacing it with public address of firewall. CS525 - Saroj Patil

  7. Solution Three approved standards – • H.460.17, • H.460.18, • H.460.19 CS525 - Saroj Patil

  8. H.460.17 • RAS over H.225 • A single TCP connection between endpoint and a gatekeeper • Addresses of RAS, Q931 and H.245 need not pass through – The messages are tunneled over the single TCP connection CS525 - Saroj Patil

  9. H.460.18 • Instead of tunneling, use of separate pinholes and extra signaling CS525 - Saroj Patil

  10. H.460.19 • Modified RTP/RTCP versions • Outgoing keep-alive messages (RTP packets with empty payload) open pinhole for incoming RTP • Outgoing RTCP packets open pinhole for incoming RTCP packets (RTCP is bi-directional) CS525 - Saroj Patil

  11. Vendors • Tandberg • Border Controller = GK + H.460.18/19 Server • MXP endpoints include H.460.18/19 Client • Polycom • V2IU servers and VSX endpoints will support H.460.18/19 in Q2/2006 • Radvision • PathFinder solution will support H.460.18/19 (Client/Server) CS525 - Saroj Patil

  12. Conclusion • H.460.18/19 is the accepted standard for H.323 FW/NAT traversal CS525 - Saroj Patil

  13. References : • http://en.wikipedia.org/wiki/H.323 • http://en.wikipedia.org/wiki/Q.931 • http://www.chebucto.ns.ca/~rakerman/articles/ig-h323_firewalls.html • http://www.h323forum.org/papers/301005_Firewall_NAT_Traversal_White_Paper.pdf • http://vide.net/conferences/spr2006/slides/schlatter_h460.pdf CS525 - Saroj Patil

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