 Any of the individual protocols can, however, be recursively discriminated further, which may result in a hierarchy of service elements in the C-dimension. The integrator is not concerned with (and does not know) what functions the protocol elements are performing in the D-dimension (integrators only see service elements). However, integrators do sometimes support addressing between proto- col elements by names. This means that a service element in one logical node can request from its integrator to be associated with a named protocol element some- where in the logical network. The integrator will find the global SAP of the logical node where that protocol element exists, and establish an association between its own service element and the remote protocol element. The association is estab- lished by message exchange between the integrators in the two logical nodes that are involved. A protocol element can use one or several association endpoints at a time. Com- pared to the permanency of SAPs, association endpoints often have a temporary existence. A temporary association endpoint is established, assigned to a protocol element and released by the activities of the integrator. Through this disintegration step we have separated the functionality of a logical node into a number of protocol elements and an integrator that manages associa- tions between its own service elements and protocol elements in other logical 2.3 Architectural Principles nodes. The protocol elements in a logical node may be functionally identical or dif- ferent, and they may have a permanent or a temporary existence in functional space. In the D-dimension a protocol element belongs to a distributed system of proto- col elements, called a protocol network. A protocol network is contained in a logi- cal network. A protocol network can be defined relatively independently from other protocol networks, both from a specification point of view, and from a configura- tion point of view. Due to the possibly temporary existence of protocol elements, a p