consequence of this generic model is that all service elements have a tem- porary existence in the logical node. The model can, of course, be modified SO that the logical node may include also permanent service elements over other permanent association endpoints. The discriminator translates between AEid and Aid. Another consequence is that service elements can terminate different protocols (PRA and PRB in Fig. 5.19). This is because the ASH uses the association proto- col to negotiate with the peer-ASH about which protocol to use. It is the responsibility of the ASH to establish an association. The scenario may look as shown in Fig. 5.20. The model shows only the scenario in the initiating node. The scenario is quite similar to the previous one: 1. A service element requests an association from the ASH. The parameter may either be a name of an SE or a request for any protocol element that operates according to the protocol PRB (AML supports both variants of associate opera- tions). The latter is assumed here. 2. The ASH finds the address to a logical node that can support the protocol. 5 Protocol Network Modelling 3. The ASH creates a message that requests an association to a PRB-SE in the remote logical node. The ASH suggests the association identifier ai1 to be used in communication between the SEs. 4. The ASH requests sending from the discriminator over the permanent associa- tion endpoint x0. Events in the scenario: type B 1 associateReq((PRB)) Find SAPI for PRB 4 sendReq(destSAPI,SDU) sendCnlReq(destSAPI,SDU) AssReq recCnlRepCnf(origSAPI,SDU) 10 ASH 2 recRepCnf(origSAPI,SDU) AssCnf 11 useOrd({AEid ,destSAPI) 12 associateCnf({AEid x1}) MTid Aid userData Discriminator MTid Aid userData CNL-CSP Fig. 5.20 Association handling scenario in a logical node 5. The discriminator sends everything that comes from the ASH on association ai0. 6. The discriminator uses the destSAPI provided by ASH for sending over the CNL-CSP. 7. A response-SDU is received from the remote logical node. 8. The discriminator reads the corre