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Commonly confused · Collaboration, Voice & AV

SIP vs H.323: What's the Difference?

SIP is an IETF text-based signaling protocol that sets up, modifies, and tears down sessions and dominates modern VoIP and video. H.323 is an older ITU-T umbrella suite of binary protocols for multimedia over IP, still found in legacy video conferencing systems.

SIPH.323
Standards bodyIETF (RFC 3261)ITU-T
EncodingText-based, HTTP-likeBinary (ASN.1)
Default portsUDP/TCP 5060, TLS 5061TCP 1720 for call setup (H.225)
ComplexitySimpler, modularComplex suite (H.225, H.245, RAS)
Key componentsUser agents, proxy and registrar serversTerminals, gateways, gatekeepers, MCUs
Media transportRTP/RTCPRTP/RTCP
Current usageDominant in IP telephony and SIP trunkingLegacy video conferencing and some gateways
Remember it

SIP talks like the web; H.323 talks like the old telecom world.

Exam tip

Know the signaling ports and that both use RTP for the actual media. Questions may describe a gatekeeper (H.323) or a registrar (SIP) and ask which protocol is in use.

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