(or type d-m-t-c on) to get two envi- ronment instances. C. Select Trace > MSC Level: Set: a Select Unit name window appears, select System V76test and press OK : a Select Trace value window appears, select 31* Block trace */ and press OK. D. Select Trace > MSC Trace: Start: select 0 1* Basic MSC */ and press OK. E. Select Execute > Command Script, choose testl.com and press OK: the Simulator executes the commands contained in testl.com, and the MSC trace contains only blocks, instead of processes, as illustrated in Figure 4.14. F. Rename the MSC: in the MSC Editor, type testl instead of SimulatorTrace. G. Save the MSC: in the MSC Editor, select File > Save As, navigate to the desired directory, enter testl.msc and press OK. H. Exit from the Simulator. 4.2.3 Detect a bug in the SDL model 4.2.3.1 Check the number of retransmissions You will check that the retransmission of SABME occurs a maximum of three times after its first transmission, as specified in Section 3.2.3. For that, you will generate an MSC trace Interactive Simulation 51 MSC Test1 block block block dataLink DLCaSU DLCa_2 dataLink_1 DLCb_3 DLCbSU L_EstabReq V76frame V76frame (SABME : (. 0.)) L_Establnd (SABME : (. 0 )) DLC number 0 established. L_EstabResp V76frame V76frame L_EstabConf (UA (.0.) ) (UA (.0.) ) L_SetparmReq V76frame V76frame (XIDcmd : 0) Exchange L_SetparmInd (XIDcmd : 0) identification (XID): SetparmResp V76frame V76frame SetparmConf (XIDresp 0) (XIDresp : 0) L_DataReq V76frame (0, 86) V76frame (.0,86,15.)) L_Datalnd Transfer of data (1 : (. 0,86,15.)) 86 through DLC (0,86) number 0: L_ReleaseReq V76frame V76frame (DISC : (. 0 )) ( DISC : (.0.)) Release of V76frame DLC number 0: V76frame (UA : (.0.) ) (UA:1.0.)) L_Releaselnd L_Releaselnd Figure 4.14 The black box MSC trace created by the Simulator containing only the process DLC in block DLCa and display the value of the retransmission counter N320cnt. A. Launch (or restart) the Simulator. B. Press the button SDL in the Trace group. C. Select Trace > MSC Level: Set: a Select Unit name