tailieunhanh - GSM Networks : Protocols, Terminology, and Implementation - Chapter 9

Tín hiệu Phần điều khiển kết nối SCCP sử dụng các lớp MTP 1 đến 3 của SS7. Trong GSM, các dịch vụ được sử dụng bởi một số hệ thống con (Hình ). Các dịch vụ của SCCP được sử dụng, đặc biệt, bởi một phần các trạm cơ sở ứng dụng hệ thống phụ (BSSAP) trên giao diện A và một phần giao dịch các ứng dụng khả năng (TCAP) cùng với phần ứng dụng di động (MAP) trên các giao diện khác nhau trong NSS. Lưu ý rằng ISUP cũng có thể sử dụng SCCP, nhưng các ứng. | 9 Signaling Connection Control Part The SCCP uses the layers MTP 1 through 3 of SS7. In GSM those services are used by a number of subsystems Figure . The services of the SCCP are used in particular by the base station subsystem application part BSSAP on the A-interface and by the transaction capabilities application part TCAP together with the mobile application part MAP on the various interfaces within the NSS. Note that ISUP also may use the SCCP but fewer and fewer applications use that combination. Tasks of the SCCP In contrast to the MTP 1 through 3 which is responsible for the transport and address functionality between two network nodes the SCCP by means of its Layer 3 functions offers end-to-end addressing even across several network nodes and countries. Additionally the SCCP allows for a distinction among the various applications within a network node internally the SCCP refers to these applications as subsystems. Two connection-oriented and two connectionless service classes are available to the users of the SCCP for actual data transfer. Furthermore the SCCP comes with its own management functions for administrative tasks which are independent from those known from the SS7 signaling network management. Although the SCCP is considered a Layer 3 functionality in the ITU Recommendations through it also provides features that belong to Layer 4 including mechanisms for error detection and an optional segmentation of the data to be transmitted. 153 154 GSM Networks Protocols Terminology and Implementation Figure The SCCP as a platform for various users. Services of the SCCP Connection-Oriented Versus Connectionless The SCCP offers two connection-oriented and two connectionless service classes to its users. The difference between the two is as follows. Two network nodes establish a virtual connection between the two subsystems for transaction 1 2 or 3 in case of the connection-oriented mode. The identification of the connection is