3G Call Flow

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Here is UMTS subscriber call flow with the core network.

MS-A                                               MSC                                                      MS-B
****************************************************************************************************
-------Initial_UE(CM_SERVICE_REQ) -->|
------------Dir_Trnx(AUTH_REQ)         <--|
-------------Dir_Trnx(AUTH_RSP)         -->|
---------------SecurityModeCmd            <--|
--------------SecurityModeComp           -->|
-----Dir_Trnx(TMSI_RELOC_CMD)   <--|
----Dir_Trnx(TMSI_RELOC_COMP)  -->|
  -------------Dir_Trnx(SETUP)            -->|
---------Dir_Trnx(CALL_PROC)        <--|
----------------RabAssignReq               <--|
----------------RabAssignRsp               -->|

                                                                     |-->  PAGING  ---------------------------    
                                                                     |<--  Initial_UE(PAGE_RSP) -------------
                                                                     |-->  Dir_Trnx(AUTH_REQ)--------------        
                                                                     |<--  Dir_Trnx(AUTH_RSP)---------------        
                                                                     |-->  SecurityModeCmd -------------------       
                                                                     |<--  SecurityModeComp------------------        
                                                                     |-->  Dir_Trnx(TMSI_RELOC_CMD)------  
                                                                     |<--  Dir_Trnx(TMSI_RELOC_COMP) ---
                                                                     |-->  Dir_Trnx(SETUP)    -------------------       
                                                                     |<--  Dir_Trnx(CALL_CONF) --------------      
                                                                     |-->  RabAssignReq   ------------------------           
                                                                     |<--  RabAssignRsp  -------------------------            
                                                                     |<--  Dir_Trnx(CALL_ALERT)  -------------   
-----------Dir_Trnx(CALL_ALERT)       <--|
                                                                     |<--  Dir_Trnx(CALL_CONNECT)----------  
                                                                     |-->  Dir_Trnx(CALL_CONNECTACK)---- 
-------Dir_Trnx(CALL_CONNECT)     <--|
---Dir_Trnx(CALL_CONNECTACK)  -->|

 <--------------------------------------Call Connected at this stage---------------------------->
                                                                      |<--  Dir_Trnx(CALL_DISCONNECT) ------
                                                                      |-->  Dir_Trnx(CALL_REL)   ------------------     
                                                                      |<--  Dir_Trnx(CALL_RELCOMP)   ----------- 
 |<--   Dir_Trnx(CALL_DISCONNECT)---
|--  Dir_Trnx(CALL_REL)-------------------->    
                                                                      |-->  IuReleaseCmd    ---------------------------          
                                                                      |<--  IuReleaseComp    --------------------------         
--------Dir_Trnx(CALL_RELCOMP)     <--|
------------------IuReleaseCmd               <--|
------------------IuReleaseComp              -->|
*************************************************************************************************

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