2 Recommendation T.122 (02/98)
– ITU-T Recommendation F.710 (1991), General principles for audiographic conference
service.
– ITU-T Recommendation T.123 (1996), Network specific data protocol stacks for multimedia
conferencing.
3 Definitions
This Recommendation defines the following terms:
3.1 MCS provider: An entity (i.e. active element) of an MCS subsystem, interacting directly
with application entities above and transport entities below. The services it provides and the services
it uses are modelled in terms of abstract primitives. An MCS provider communicates with peer MCS
providers.
3.2 MCS domain: A tree of MCS connections among MCS providers or, in the degenerate case,
part of a single MCS provider. The MCS providers involved are said to host the domain. A domain
sets the boundary for data transfer among attached MCS users.
3.3 MCS domain selector: An octet string that distinguishes multiple domains hosted by the
same MCS provider. The creation of MCS providers, their configuration to host one or more
domains, and the internal structure of domain selectors are all local matters.
3.4 top MCS provider: In every domain a single MCS provider will become the Top MCS
Provider and will be the exclusive manager of all the domain's channel, user Ids and token resources.
3.5 MCS connection: A specified set of transport connections, managed as one unit, between a
pair of MCS providers. Each end of an MCS Connection is bound to a respective MCS domain
selector. One end of each MCS Connection is designated to be hierarchically superior to the other.
3.6 MCS user: An application entity obtaining services from an MCS provider. Once they have
been attached to the same domain, MCS users can transfer data in point-to-point or multicast fashion.
3.7 MCS Service Access Point (MCSAP): A point through which an MCS user accesses an
MCS provider.
3.8 MCS attachment: A multi-connection end point within an MCSAP. Each MCS attachment
is bound to an MCS domain selector. An MCS user may attach through an MCSAP to domains
hosted by the MCS provider.
3.9 MCS user Id: A short identifier, unique within an MCS domain, that distinguishes between
MCS attachments. A user with multiple attachments to the same domain, through the same or
different SAPs, has equally many user Ids.
3.10 control-MCSAP: A unique MCSAP per MCS provider (distinguished by some local means)
to which the MCS Connect and MCS Disconnect primitives are restricted. The MCS user of a
Control-MCSAP does not have direct access to data transfer through the MCS Connection end points
it contains; this is limited to the MCS provider. It is a local option whether a Control-MCSAP may
also contain MCS attachments like ordinary MCSAPs and allow the MCS user to invoke other MCS
primitives.
3.11 MCS channel: A channel is a domain-wide address. Channels are used for MCS data unit
distribution lists. All users who are members of the same channel will receive data sent to that
channel.
3.12 MCS private channel: A channel with an authorized group of users. Only they may send
and receive data over the channel. Attempts by unauthorized users to invoke an MCS primitive
involving a private channel as parameter will fail.