Khả năng giao dịch và phần ứng dụng di động TCAP và MAP là "trên" của SS7 (MTP 1-3) và SCCP, cơ sở tín hiệu trên tất cả các giao diện NSS. Cả hai đều bị xử lý trong một chương này, bởi vì các chức năng của MAP không thể hiểu được nếu không biết về các TCAP. TCAP, với Layer 4 đến 6 cung cấp MAP GSMspecific với một giao diện chuẩn hóa các phương tiện truyền dẫn và SS7. Các biên giới tách biệt rõ ràng giữa TCAP và MAP, như thể hiện trong hình , trong thực. | 11 Transaction Capabilities and Mobile Application Part The TCAP and the MAP are on top of SS7 MTP 1 3 and SCCP the basis for signaling on all NSS interfaces. Both are dealt with in this one chapter because the functionality of the MAP cannot be understood without knowing about the TCAP. The TCAP with its Layers 4 through 6 provides the GSM-specific MAP with a standardized interface to the transmission medium and to SS7. The clearly separated border between TCAP and MAP as shown in Figure is in practice more difficult to identify. The transition between the two layers is rather fuzzy. An essential precondition to understanding MAP is the study of TCAP. Above MAP there are the applications themselves in the GSM case there are the NSS subsystems HLR VLR MSC and EIR. Transaction Capabilities Application Part TCAP uses SS7 or more precisely the SCCP as shown in Figure . The TCAP protocol is to some extent the most important piece of the protocol stack for GSM or any other mobile system because it provides the core functionality to support roaming. Like the SCCP TCAP is not restricted to being used by only mobile services but is utilized by many other applications for database access and similar tasks. In that respect TCAP is different from all previously presented protocols. TCAP allows its users to access databases and switching exchanges via the worldwide SS7 network and to invoke services or modify parameters. That does 185 186 GSM Networks Protocols Terminology and Implementation Layer 7 Layer 4-6 Layer 3 Figure Positioning of MAP and TCAP in the SS7 protocol stack. not exclude TCAP from being used as a platform for pure data transfer as in GSM after an inter-MSC handover. TCAP is the typical implementation of the OSI layers 4 through 6. In that function it allows integration of some translation functionality into a message for instance to provide a means for users of a transaction to discuss or synchronize on an application protocol. An example
