This Recommendation provides a functional description of the Bearer Independent Call Control
(BICC) protocol. The BICC protocol provides the signalling functions required to support
narrowband ISDN services independent of the bearer technology and signalling transport technology
used.
The BICC protocol uses the Signalling Transport Converter (STC) layer for signalling message
transport. The Generic Signalling Transport Service is described in ITU-T Q.2150.0 [31]. The STCs
are defined in other Recommendations in the Q.2150.x family of Recommendations.
Several arrangements are possible for nodes that support BICC signalling. These nodes may have an
associated Bearer Control Function (BCF) in which case they are referred to as Serving Nodes (SN).
A node without an associated BCF is referred to as Call Mediation Node (CMN). Between Serving
Nodes the control of bearers is provided by other protocols - not specified by this Recommendation.
In a Serving Node (SN), the Call Service Function and the Bearer Control Function (BCF) entities
may be physically separated. The Call Bearer Control (CBC) signalling is used between these two
entities in case of physical separation. The CBC protocol is specified in ITU-T Q.1950 [61].
Bearer control signalling can be deployed over a separate signalling transport or the Bearer Control
Protocol (BCP) can be tunnelled over the "horizontal" BICC protocol between peer CSFs and the
"vertical" CBC interface between a CSF and a BCF. The Bearer Control Tunnelling Protocol is
specified in ITU-T Q. 1990 [62].
Both SNs and CMNs are modelled using the "Half Call" modelling technique. Every call processing
scenario is thus divided between an incoming and an outgoing signalling procedure. In the scope of
this Recommendation at least one of these procedures is the BICC procedure (see Figures 1 and 2).