 of SCCP. You can read more about that in Sect 3.4.5.2). The way SSN is used assumes that all actors that belong to the same actor layer are identi- fied by the same SSN value. Since SCCP uses the SSN to identify using layers other than TCAP as well, the way the SSN is used when configuring layers on SCCP becomes rather complicated. Furthermore, since TCAP has no addressing system for TC user identification, actor layers that rely on TCAP are actually con- figured on the SCCP level by binding the identification of TCAP actors to SCCP addressing (a violation of general transparency requirements on layer structures). Note that since the SSN only identifies a TC user within a TCAP layer element, an MTP L3 (the datagram switching layer in SS7) address has to be given as part of destAddr an origAddr as well. This address, called destination point code (DPC), identifies the SS7 node in which the TCAP layer element exists. We will end this discussion by commenting on the fact that while AMLn needs only two meta-primitives and ROSE nine, TCAP needs 15 (see "component han- dling operations" in Fig. 6.4) for the same network function. There are three main reasons for that: 6.3 TCAP, the Transaction Capability Application Part in SS7 1. The ROSE operation RO-RESULT is substituted by two operations in TCAP: TC-RESULT-L (only response or last part of a segmented response) and TC- RESULT-NL (non-final part of a segmented response). This is an effect of that TCAP does not necessarily run on a layer that accepts unlimited size of a user datum (as the OSI presentation layer does). For example, when TCAP runs on SCCP it uses an SCCP service that does not segment user data (allows only about 300 octets per invocation). This solution implies that the TC user must know which connectivity layer TCAP uses, which again is a violation of the transparency requirement of layer structures. A more user friendly TCAP had defined an optional segmentation function in the agent layer. 2. There exist three operations that have no correspondence i