ITU-T Standards and Recommendations
H.323 V2 Packet-based multimedia communications systems
H.225.0 Call signalling protocols and media stream packetization for packet-based multimedia (includes Q.931 and RAS)
H.225.0 Annex G Gatekeeper to gatekeeper (inter-domain) communications
H.245 Control protocol for multimedia communications
H.235 Security and encryption for H-series multimedia terminals
H.450.x Supplementary services for multimedia: 1. Generic functional protocol for the support of supplementary services in H.323 2. Call transfer 3. Diversion 4. Hold 5. Park & pickup 6. Call waiting 7. Message waiting indication
H.323 Annex D Real-time fax using T.38
H.323 Annex E Call connection over UDP
H.323 Annex F Single-use device
T.38 Procedures for real-time group 3 facsimile communications over IP networks
T.120 series Data protocols for multimendia conferencing
IETF RFCs and Drafts
RFC 2543 SIP: Session initiation protocol
RFC 2327 SDP: Session description protocol
Internet Draft SAP: Session announcement protocol

Gateway Control

H.GCP Proposed recommendations for gateway control protocol
Internet Draft MGCP: Media gateway control protocol
Internet Draft MEGACO protocol
Draft SGCP: Simple gateway control protocol
Internet Draft IPDC: IP device control

Media Transport


RFC 1889 RTP: Real-time transport protocol
RFC 1889 RTCP: Real-time transport control protocol
RFC 2326 RTSP: Real-time streaming protocol

Media Encoding

ITU Voice
Standard Algorithm Bit Rate (Kbit/s) Typical end-to- end delay (ms) (excluding channel delay) Resultant Voice Quality
G.711 PCM 48, 56, 64 <<1 Excellent
G.723.1 MPE/ACELP 5.3, 6.3 67-97 Good(6.3), Fair(5.3)
H.728 LD-CELP 16 <<2 Good
G.729 CS-ACELP 8 25-35 Good
G.729 annex A CS-ACELP 8 25-35 Good
G.722 Sub-band ADPCM 48, 56, 64 <<2 Good
G.726 ADPCM 16,24,32,40 60 Good(40), Fair(24)
G.727 AEDPCM 16, 24, 32, 40 60 Good(40), Fair (24)
Standard Algorithm Bit Rate (Kbit/s) Picture Quality
H.261 Discrete cosine transform (DCT) with motion compensation px64 (p=# of ISDN B channels) Low
H.263 Improved version of H.261 Various Medium
Additional Information