ic operations and the primitives defined in CORBA, see Orfali et al. (1996). CORBA is designed 4 Physical Network Modelling for distributed object applications. Therefore, there are also considerable differ- ences. Among other things, CORBA has no locRec, and it has two versions of sen- dRec, one blocking (invoke) and one non-blocking (send, get_response). Our node platform in Fig. 4.22 does not support object communication. Therefore, we can deal effectively with simpler operations. The operations of the global SAP are some or all of the operations we defined in Sect. 3.2.5. The first mapping example, see Fig. 4.23, shows in pseudo-code how the global synchronous receive operation srecREQUEST is handled by the MEH. srecREQUEST is a receive operation that may be used by the logical node in A- EVH to access global SDUs from the logical node in B-EVH. A-EVH A-MEH 1. gevOrd(srecReq(...)) 2. createLocalPdu(srecReq(...) 3. T1=timer-value 4. sendRec(in B, T1, localSDU;out resp) 5. Case resp time-out >devRepCnf(timeOutRepCnf(...) Case localPDU not srecREQ -> Case ASPtype Confirm devRepCnf(srecCnf(globalSDU)) Refuse devRepCnf(srecRef(...)) Fig. 4.23 An implementation of the use of srecREQUEST 1. The A-EVH calls the logical node in the B-EVH by executing a gevOrd. The parameters of the gevOrd are the information elements of a global srecRequest. 2. The A-MEH creates a local PDU. Here it is assumed that no fragmentation is needed, and that the service of the CSP is reliable. Therefore, A-MEH only needs to sequence the data and encode them (which is done by the procedure createLocalPdu). Otherwise, the A-MEH might also need to fragment the data into several local PDUs and to add parameters in the PDUs for error handling. 3. A timer value is selected (may be delivered as a parameter in the gevOrd). 4. The A-MEH executes a sendRec. The local address of the B-MEH is B. localSDU is the bit-representation of a localPDU. 5. A response is delivered. 6. The response might be a time-out, which indicates that the logical node in B- E