H.323 'Ports'

• TCP port 1718 for Gatekeeper discovery
• TCP port 1719 for Gatekeeper RAS
• TCP port 1720 for call setup and call signalling
• ‘Dynamic’ UDP ports 1024-65535 for media streams (RTP and RTCP)

H.323 Draft Annexes (Click for those available)

• Annex D - Real Time fax over H.323
• Annex E - Multiplexed call signalling
• Annex F - Simple Endpoint Terminal (SET)
• Annex G - Text SET
• Annex H - Mobility
• Annex I - Operation over low QoS Networks
• Annex J - Secure SET
• Annex K - HTTP Service Control Transport
• Annex L - Stimulus Signalling
• Annex M - QSig, ISUP, DSS1 Tunneling in H.323
• Annex P - Modem signals over H.323
• Annex Q - Camera Control
• Annex R - Robustness for H.323 entities
  

Applications (roll over)

• Business Telephony Services
• MS Netmeeting
• Video Conferencing
• Internet Gateways

H.323 Sub-Standards (Click)

• H.225.0 - call control protocol
• H.235 - security
• H.245 - media control protocol
• Q.931 - digital subscriber signalling
• H.450 - Supplementary Services

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H.323 holds together a suite of standards defined to provide for transmission of voice and other real time media (video) via packet based network infrastructures such as IP. Available since 1996, H.323 is defined and developed by the ITU Study Group 16, and is still the most deployed VoIP standard in use today. Current Version of H.323 is V5 released Q2 2003, with additional services covered by H.450, H.460 and H.5xx.

H.323 ITU-T - Core (Click)

• H.323 v1 (1996)
• H.323 v2 (1998)
• H.323 v3 (1999)
• H.323 v4 (2000)
• H.323 v5 (2003)