Ø Technology
to enable voice communication over the IP network became known as Voice over
Internet Protocol or VoIP, in short.
Ø Today,
there are two sets of standards for VoIP switching, media, and gateways. These
are H.323 from International Telecommunications Union (ITU) and Session
Initiation Protocol (SIP) from Internet Engineering task Force (IETF).
v H.323 in VoIP – MCU
Ø The
Multipoint Control Unit (MCU) supports conferences between three or more
endpoints. An MCU consists of a Multipoint Controller (MC) and a Multipoint
Processor (MP).
Ø The
MC handles H.245 negotiations between all terminals to determine common
capabilities for audio and video processing. An MCU optionally may have one or
more MPs to deal with the media streams.
Ø MP
mixes, switches, and processes audio, video, and/or data bits.
v SIP in VoIP
Ø The
Session Initiation Protocol (SIP) is a signaling protocol fortelephone calls
over IP. SIP is defined by the IETF and is gaining popularity.
Ø Unlike
the H.323, SIP is designed specifically for the Internet.
Ø SIP
defines interfaces for establishing, modifying and terminating sessions with
one or more participants in the VoIP environment. It facilitates development of
telephony application.
Ø SIP
supports the following facets of establishing and terminating multimedia
communications: User location; User capabilities; User availability; Call
setup; Call handling, and Call teardown.
