 the OSI RM, which is why this form of partitioning is regarded as "horizontal partitioning." 3.1 Introduction Logical node is n11 Logical Connection created by node is n12 the connectivity stratum Standardized and manageable Connectivity layer interface stratum is nw0 Hide nw0 Logical network is nw1= {n11,n12} Fig. 3.2 A possible logical network in the OSI RM, L=layer dimension; N=node dimension; NO=logical-node dimension; n...=(logical) node name; nw...=(logical) network identifier The two logical nodes n11 and n12 are created by horizontal partitioning of the model in Fig. 3.1. We then used the fact that all layers below exist only to create some kind of logical connections for layer 4, on which layers 5 through 7 also depend. A logical connection is the equivalence to a connection over a physical media in the OSI layer model. If we can specify how this logical connection is cre- ated and used, we can also disregard all layer and network structures below the layer 3/4 interface, which we regard as just a logical network (nw0) that offers a defined type of connections. As a result we can define the logical network nw1 as depicted in Fig. 3.2. For this logical network to make sense in network manage- ment, the layer 3/4 interface must be standardized as some kind of network inter- face. Note also that each logical network must have its own N dimension, since it exists only in some of the nodes of a network. This is why we introduce the logical- node dimension (NO), i.e., we let each logical network define its own structure of logical nodes. A complex layer structure (e.g., the OSI layer structure) may also be horizon- tally partitioned on several levels by defining more than one layer interface as net- work interfaces, resulting in a structure of nested logical networks (see Fig. 3.3). Note that, at the extreme, each layer in a layer structure can define a logical net- work. The connection between logical nodes on a higher level depends on connections on a lower level (this is the essence of the OSI RM layer con