If the Voice over IP standards abbreviations and acronyms seem like the alphabet soup here’s a listing of protocols/standards and a short description that might help:

Signaling

H.323 H.323Megaco H.248  Gateway Control ProtocolMGCP  Media Gateway Control ProtocolRVP over IP Remote Voice Protocol Over IP SpecificationSAPv2 Session Announcement ProtocolSGCP Simple Gateway Control ProtocolSIP Session Initiation ProtocolSkinny Skinny Client Control Protocol (Cisco)

Media

DVB Digital Video BroadcastingH.261 Video stream for transport using the real-time transportH.263 Bitstream in the Real-time Transport ProtocolRTCP RTP Control protocolRTP Real-Time Transport

H.323 Protocols Suite

H.225 Covers narrow-band visual telephone servicesH.225 Annex GH.225EH.235 Security and authenticationH.323SETH.245 Negotiates channel usage and capabilitiesH.450.1 Series defines Supplementary Services for H.323H.450.2 Call Transfer supplementary service for H.323H.450.3 Call diversion supplementary service for H.323H.450.4 Call Hold supplementary serviceH.450.5 Call Park supplementary serviceH.450.6 Call Waiting supplementary serviceH.450.7 Message Waiting Indication supplementary serviceH.450.8 Calling Party Name Presentation supplementary serviceH.450.9 Completion of Calls to Busy Subscribers supplementary serviceH.450.10 Call Offer supplementary serviceH.450.11 Call Intrusion supplementary serviceH.450.12 ANF-CMN supplementary serviceRAS Manages registration, admission, statusT.38 IP-based fax service mapsT.125 Multipoint Communication Service Protocol (MCS)

SIP Protocols

MIMESDP Session Description Protocol

SIP Session Initiation Protocol