SS7 Layer

BICC
Bearer Independent Call Control protocol is a call control protocol used between serving nodes. This protocol is based on the ISUP protocol, and was adapted to support the ISDN services independent of the bearer technology and signalling message transport technology used.

BISUP
The B-ISDN User Part (B-ISUP) is applicable to international B-ISDN networks. In addition, the B-ISDN User Part is suitable for national applications. Most messages and parameters specified for international use are also required in typical national applications. Moreover, coding space has been reserved in order to allow national administrations and recognized operating agencies to introduce network specific signalling messages and parameters within the internationally standardized protocol structure.

DUP
The Data User Part (DUP) defines the necessary call control, and facility registration and cancellation related elements for international common channel signalling by use of Signalling System No. 7 for circuit-switched data transmission services. The data signalling messages are divided into two categories:

• Call and circuit related messages: used to set up and clear a call or control and supervise the circuit state.
• Facility registration and cancellation related messages: used to exchange information between originating and destination exchanges to register and cancel information related to user facilities.

ISUP
ISUP is the ISDN User Part of SS7. ISUP defines the protocol and procedures used to setup, manage and release trunk circuits that carry voice and data calls over the public switched telephone network. ISUP is used for both ISDN and non-ISDN calls. Calls that originate and terminate at the same switch do not use ISUP signalling. ISDN User Part messages are carried on the signalling link by means of signal units. The signalling information field of each message signal unit contains an ISDN User Part message consisting of an integral number of octets.

MAP
Mobile Application Part (MAP) messages sent between mobile switches and databases to support user authentication, equipment identification, and roaming are carried by TCAP In mobile networks (IS-41 and GSM) when a mobile subscriber roams into a new mobile switching center (MSC) area, the integrated visitor location register requests service profile information from the subscriber's home location register (HLR) using MAP (mobile application part) information carried within TCAP messages.

MTP-2
Message Transfer Part - Level 2 (MTP-2) is a signalling link which together with MTP-3 provides reliable transfer of signalling messages between two directly connected signalling points.

MTP-3
Message Transfer Part - Level 3 (MTP-3) connects Q.SAAL to the users. It transfers messages between the nodes of the signalling network. MTP-3 ensures reliable transfer of the signalling messages, even in the case of the failure of the signalling links and signalling transfer points. The protocol therefore includes the appropriate functions and procedures necessary both to inform the remote parts of the signalling network of the consequences of a fault, and appropriately reconfigure the routing of messages through the signalling network.

Q2140
The SSCF for NNI Signaling standard consists of the Service Specific Coordination Function (SSCF) in conjunction with the Service Specific Connection Oriented Protocol (SSCOP) which defines the Service Specific Convergence Sublayer (SSCS). The purpose of the Service Specific Coordination Function is to enhance the services of SSCOP to meet the needs of the requirements of the NNI level 3 protocol. In addition the SSCF at the NNI provides communication with Layer Management for proper operation of signalling links.
The SSCF at the NNI is the uppermost sub-layer in the protocol stack for the SAAL at the NNI. By construction, it utilizes the services of the underlying SAAL sub-layers, in combination with its own functions, to provide an overall SAAL service to the SAAL user, as described below.
The SAAL at the NNI provides signalling link functions for the transfer of signalling messages over one individual signalling data link. The SAAL functions provide a signalling link for reliable transfer of signalling messages between two signalling points.
A signalling message delivered by the higher levels is transferred over the signalling link in variable length Protocol Data Units (PDUs). For proper operation of the signalling link, the PDU comprises transfer control information in addition to the information content of the signalling message.

SCCP
The Signalling Connection Control Part (SCCP) offers enhancements to MTP level 3 to provide connectionless and connection-oriented network services, as well as to address translation capabilities. The SCCP enhancements to MTP provide a network service which is equivalent to the OSI Network layer 3.

TCAP
TCAP (Transaction Capabilities Application Part) enables the deployment of advanced intelligent network services by supporting non-circuit related information exchange between signalling points using the SCCP connectionless service. TCAP messages are contained within the SCCP portion of an MSU. A TCAP message is comprised of a transaction portion and a component portion.
A TCAP message is structured as a single constructor information element consisting of the following: Transaction Portion, which contains information elements used by the Transaction sub-layer; a Component Portion, which contains information elements used by the Component sub-layer related to components; and, optionally, the Dialogue Portion, which contains the Application Context and user information, which are not components. Each Component is a constructor information element.

TUP
The Telephone User Part (TUP) carries the telephone user messages on the signalling data link by means of signal units.
The signalling information of each message constitutes the signalling information field of the corresponding signal unit and consists of an integral number of octets. It basically contains the label, the heading code and one or more signals and/or indications.
The service information octet comprises the service indicator and the subservice field.
The service indicator is used to associate signalling information with a particular User Part and is only used with message signal units (see Recommendation Q.704, § 12.2).
The information in the subservice field permits a distinction to be made between national and international signalling messages. In national applications when this discrimination is not required possibly for certain national User Parts only, the subservice field can be used independently for different User Parts.