H.323 VoIP Framework
H.323 remains in enterprise video conferencing (Cisco, Polycom legacy endpoints) and some carriers. Understanding it is necessary when integrating with legacy infrastructure or gateways.
What It Defines
H.323 is the ITU-T umbrella standard for packet-based multimedia communications over LANs. Defines terminal, gateway, gatekeeper, and MCU components; uses H.225/Q.931 for call signaling, H.245 for capability exchange and media control, and RTP/RTCP for media transport. Largely superseded by SIP but still present in legacy enterprise video.
Canonical (Normative)
The international standards body for telecommunications under the UN umbrella. Publishes Recommendations in series (E, G, H, Q, T, X…): E.164 phone numbering, G.711/G.722 audio codecs, H.323 VoIP framework, and G.9959 (Z-Wave). Free access to most Recommendations.
Related Specs
SIP is the PSTN of the internet. Every VoIP platform (Twilio, Vonage, AWS Chime, Asterisk, FreeSWITCH) speaks SIP. Building any communications product requires understanding INVITE flows, registration, and codec negotiation via SDP.
RTP carries all real-time media: VoIP, WebRTC, live video, and video conferencing. Understanding SSRC demultiplexing, jitter buffers, and RTCP feedback loops is essential for any media application.