iscrepancy is not accidental, but reflects a choice between the main functions that an integrator can perform: discrimination, message handling, associ- ation handling and relaying. The way these functions are implemented depends on a number of factors, including the type of CSP used by the logical node. It is also strongly dependent on the type of protocol that the integrator supports. Discrimination 5.3.1 Introduction There are two properties that can be used to classify the discrimination function in a logical node: Number of discrimination levels. If a logical node has no internal structure of service elements, we say that the discrimination level is 0. If the logical node has a flat structure of service elements, the discrimination level is 1. Some protocol networks may implement additional discrimination between internal objects, which case we say that the discrimination level is 2, and SO forth. Considering what we know about different types of CSPs, one can identify four aspects of a network architecture that can be used to provide discrimination inside logical nodes. We call such aspects discrimination qualifiers. Discrimina- tion between service elements of a logical node can be provided based on addresses, identified by SAP identifiers (SAPI). An alternative is to used con- nections, identified by connection endpoint identifiers (CEI). A third method is to identify service elements by names¹. These names represent reference points on different discrimination levels. The last option is to base discrimination on message type, identified by a mes- sage type identifier (MTid). A name differs from an address in that it is not related to routing. This implies that names do not change when addresses are changed, and that using names for identifying communication partners requires a name-address translation function. For example, the global title offered by SCCP is a name, while the MTP point code, combined with the subsystem number, is an address. In this case SCCP provides the name-address translation functi