H.323 Multipoint Conferences
H.323 defines three types of multipoint conferences, as apparent in Figure 5-11: centralized,
decentralized (or sometimes alleged distributed), and ad hoc. H.323 additionally defines a
hybrid of the aboriginal two.
All types of multipoint conferences await on a distinct MC to alike the associates of
a conference. Each endpoint has an H.245 ascendancy approach affiliation to the MC. Either
the MC or the endpoint initiates the ascendancy approach setup. H.323 defines the following
three types of conferences:
■ Centralized multipoint conference: The endpoints charge accept their audio, video, or
data channels affiliated to a multipoint processor (MP). The MP performs mixing
and switching of the audio, video, and data, and if the MP supports the capability,
each endpoint can accomplish in a altered mode.
Figure 5-11 Multipoint Conferences
■ Broadcast multipoint conference: The endpoints do not accept a affiliation to an
MP. Instead, endpoints multicast their audio, video, and abstracts streams to all participants
in the conference. Because an MP is not accessible for switching and mixing,
any bond of the appointment streams is a action of the endpoint, and all endpoints
must use the aforementioned advice parameters.
To board situations in which two streams (audio and video) would be handled
by the altered multipoint appointment models, H.323 defines a “hybrid.” A
hybrid describes a bearings in which the audio and video streams are managed by a
single H.245 ascendancy approach with the MC, but area one beck relies on multicast
(according to the broadcast model) and the added uses the MP (as in the centralized
model).
■ Ad hoc multipoint conference: Any two endpoints in a alarm can catechumen their relationship
into a point-to-point conference. If neither of the endpoints has a collocated
MC, the casework of a attendant are used. When the point-to-point appointment is
created, added endpoints become allotment of the appointment by accepting an invitation
from a accepted participant, or the endpoint can appeal to accompany the conference.