|Request received                       
                               |pass to TU                             
                               V                                       
                         +-----------+                                 
                         |           |                                 
                         | Trying    |-------------+                   
                         |           |             |                   
                         +-----------+             |200-699 from TU    
                               |                   |send response      
                               |1xx from TU        |                   
                               |send response      |                   
                               |                   |                   
            Request            V      1xx from TU  |                   
            send response+-----------+send response|                   
                +--------|           |--------+    |                   
                |        | Proceeding|        |    |                   
                +------->|           |<-------+    |                   
         +<--------------|           |             |                   
         |Trnsprt Err    +-----------+             |                   
         |Inform TU            |                   |                   
         |                     |                   |                   
         |                     |200-699 from TU    |                   
         |                     |send response      |                   
         |  Request            V                   |                   
         |  send response+-----------+             |                   
         |      +--------|           |             |                   
         |      |        | Completed |<------------+                   
         |      +------->|           |                                 
         +<--------------|           |                                 
         |Trnsprt Err    +-----------+                                 
         |Inform TU            |                                       
         |                     |Timer J fires                          
         |                     |-                                      
         |                     |                                       
         |                     V                                       
         |               +-----------+                                 
         |               |           |                                 
         +-------------->| Terminated|                                 
                         |           |                                 
                         +-----------+