Signaling & Network Control Dr. Eng. Amr T. Abdel-Hamid NETW 704 Winter 2006 SCCP + TCAP

Amr Talaat, 2006 Signaling Connection Control Part (SCCP)

Amr Talaat, 2006 SCCP Usage SCCP provides the following additional capabilities over the MTP:  Enhances MTP to meet OSI Layer 3  Powerful and flexible routing mechanisms  Enhanced transfer capability, including segmentation/reassembly when message is too large to fit into one Message Signal Unit (MSU)  Connectionless and connection-oriented data transfer services  Management and addressing of subsystems (primarily database- driven applications)

Amr Talaat, 2006 MOBILE SCCP Architecture Base Station Subsystem Mobile Application Part (BSSMAP), Direct Transfer Application Part (DTAP) use it to transfer radio-related messages in GSM.

Amr Talaat, 2006 SCCP Architecture

Amr Talaat, 2006 SCCP Architecture SCCP connection-oriented control (SCOC)  Responsible for setting up and releasing a virtual connection between two SCCP users.  offers features including sequencing, flow control, and segmentation and can override congestion procedures by assigning data priority. SCCP connectionless control (SCLC)  Responsible for transferring data between SCCP users without creating a virtual connection. SCCP routing control (SCRC)  Provides additional routing beyond that offered by MTP3, through the use of global titles. SCCP management (SCMG)  Responsible for tracking application status and informing SCMG at other SCCP nodes, as necessary.

Amr Talaat, 2006 SCCP Message Transfer Services The SCCP provides two categories of service for data transfer: connection-oriented services and connectionless services. Within each service are defined as follows:  Class 0: Basic connectionless class  Class 1: In-sequence delivery connectionless class  Class 2: Basic connection-oriented class  Class 3: Flow control connection-oriented class

Amr Talaat, 2006 Service Classes

Amr Talaat, 2006 Connection Oriented SCCP A establishes a logical connection by sending a Connection Request (CR) message to SCCP B and assigning a SLR to the request. The remote node confirms the connection by sending a Connection Confirm (CC) message and includes its own SLR and a DLR that is equal to SCCP A's SLR. The subsequent data message DT1 only needs to send the DLR because the logical connection has been established through the proceeding exchange of SLR and DLR.

Amr Talaat, 2006 SCCP Routing Control (SCRC) SCRC performs the following three functions:  Routes messages received from the MTP to appropriate local subsystem.  Routes messages from local subsystems to other local subsystems.  Routes messages from local subsystems to subsystems in remote nodes by utilizing MTP's transport services. The following are different types of network addressing that SCCP supports:  Point Code (PC) routing (MTP ROUTING)  Subsystem Number (SSN) routing  Global Title (GT) routing

Amr Talaat, 2006 Subsystem Number (SSN) routing Subsystem is an application that uses SCCP. Applications are predominantly database driven, except where ISUP is the subsystem (for a limited number of supplementary services), or where BSSAP uses SCCP (for radio-related signaling in GSM) SSN is placed inside the CdPA parameter. The SSN of the originating subsystem is also included in the Calling Party Address (CgPA) parameter to identify the subsystem that sent the SCCP message.

Amr Talaat, 2006 Global Title Routing "A global title is an address, such as dialed-digits, which does not explicitly contain information that would allow routing in the SS7 network.“ Example: 1800 A GT is a telephony address. As such, the GT address must be translated into an SS7 network address (DPC+SSN) before it can be finally delivered. The GT is placed in the global title address information (GTAI) parameter within the CgPA and CdPA fields. the SP that has been requested by another SP to perform GTT does not have to know the exact final destination of a message. Instead, it can perform intermediate GTT, in which it uses its tables to locate another SP that might have the final address required in its routing tables.

Amr Talaat, 2006 Global Title Routing

Amr Talaat, 2006 Transaction Capabilities Application Part (TCAP) Allows services at network nodes to communicate with each other using an agreed-upon set of data elements. Provides a generic interface between services that is based on the concept of "components." Components comprise the instructions that service applications exchange at different nodes. Transactions Components

Amr Talaat, 2006 Generic Service Interface TCAP is designed to be generic to accommodate the needs of a wide variety of different services. Some common services that use TCAP include number translation services. Custom Local Area Signaling Services (CLASS), Mobile Wireless, and Advanced Intelligent Network (AIN) services. Most TCAP services can be viewed as a dialogue of questions and answers. A switch needs additional information that is associated with call processing, or with a particular service that causes it to send a TCAP query that requests the needed information.

Amr Talaat, 2006 Transaction is a set of related messages that are exchanged between application processes at two different nodes. a node can have many simultaneous transactions in progress and send and receive multiple TCAP messages. When a node sends a message and expects a reply, the sending node establishes and maintains a Transaction ID. This allows an incoming message to be properly associated with previously sent messages. Transactions always begin with an initiating TCAP message that contains an Originating Transaction ID. When the service has completed, the Transaction ID becomes available for use again by the application.

Amr Talaat, 2006 Transaction Message Types

Amr Talaat, 2006 Transaction Message Types

Amr Talaat, 2006 Transaction ID

Amr Talaat, 2006 Transaction ID

Amr Talaat, 2006 Transaction ID Releasing Transaction IDs transactions end in one of two ways: either with a terminating message or a prearranged end.

Amr Talaat, 2006 Components Components are a means of invoking an operation at a remote node. A TCAP message can contain several components, thereby invoking several operations simultaneously. The TCAP component is based on the ITU X.410 specification for Remote Operations in Message Handling Systems  Invoke: Requests an operation to be performed  Return Result: Reports the successful completion of a requested operation  Return Error: Reports the unsuccessful completion of a requested operation  Reject: Reports a protocol violation, such as an incorrect or badly-formed OPDU

Amr Talaat, 2006 Components